Synth-DIY Yahoo! Groups Archives

drill pcb

2016-02-21 by rfmicrowave1@...

hello to the group I wanted to know what would be a low cost-effective solution to drill pcb ? I had found this on ebay
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080

PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustabl...

PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080 in | eBay

View on www.ebay.it

Preview by Yahoo

Thank
Roberto

Re: [Homebrew_PCBs] drill pcb

2016-02-22 by DJ Delorie

"rfmicrowave1@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
writes:

> hello to the group I wanted to know what would be a low cost-effective
> solution to drill pcb ? I had found this on ebay

You can't beat free... (assuming you have the dremel already)

http://www.delorie.com/pcb/dremel-stand/

Hello Roberto

For the price it is really a machine which should work for PCB drilling. Should it have a bit of wobble, you can still change the chuck against a good self tightening chuck closing down to almost zero. If I did not already had a precision machine for drilling my pcb's, I would buy it and replace the UK power plug - hihi. Thanks for the link.

I am sure that this drilling machine is far, far better than the Dremel assembly of Mr. Delorie.

Rgds
Jean-Claude

Am 21.02.2016 um 10:09 schrieb rfmicrowave1@... [Homebrew_PCBs]:

hello to the group I wanted to know what would be a low cost-effective solution to drill pcb ? I had found this on ebay
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080

PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustabl...
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080 in | eBay

View on www.ebay.it

Preview by Yahoo

Thank
Roberto

Re: drill pcb

2016-02-22 by bobledoux@...

This drill is sold in the USA by Harbor Freight. I have one. I use it for drilling PCB's.

There is too much run out for carbide bits. It works well with steel bits. The chuck will hold .020 or 0.5mm drill bits or larger bits.

My speed control quit working. So I wired it as a switch. So mine operates as a single speed motor, but it has variable speed adjustment with the belt pulleys.

Re: drill pcb

2016-02-22 by craigl2@...

How much runout does it have? And, how much runout is too much.?

I ask this because while I was in the process of building a inverted drill (to drill PCBs from the bottom up) at one point I had a runout of at least .01 inches. This is probably much more than your average Dremel. Despite this I was able to drill holes down to .0225 (#74 drill) using carbide drills without breaking any bits. Admittedly I was using 45X magnification to align the board and was watching as the drill broke through, therefore I did not plunge the drills to half or more of their length.

I seriously doubt that the problem people are having with drill breakage using Dremels is due simply to runout. I also don't doubt that they are having better results with other tools such as Proxxon rotary tools.

The reason I mention this is that it would be difficult for the average person to improve the runout of tools such as the Dremel but if another cause for drill breakage was found perhaps that could be easily corrected.

Craig

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-22 by <n0tt1@...>

The Harbor Freight models don't look the same as the one from GB.

Do you have a HF model number of the one you have?

Thanks,

Charlie

On 22 Feb 2016 06:25:46 -0800 "bobledoux@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> writes:

This drill is sold in the USA by Harbor Freight. I have one. I use it for drilling PCB's.

There is too much run out for carbide bits. It works well with steel bits. The chuck will hold .020 or 0.5mm drill bits or larger bits.

My speed control quit working. So I wired it as a switch. So mine operates as a single speed motor, but it has variable speed adjustment with the belt pulleys.

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-22 by Harvey White

On 22 Feb 2016 07:55:32 -0800, you wrote:

>How much runout does it have? And, how much runout is too much.?

Some of this you can see. (for the too much) My opinion is that if
you can see the drill wobble, (and especially if the very fine drill
wobbles more than its own diameter), that's too much.

>
>I ask this because while I was in the process of building a inverted drill (to drill PCBs from the bottom up) at one point I had a runout of at least .01 inches. This is probably much more than your average Dremel. Despite this I was able to drill holes down to .0225 (#74 drill) using carbide drills without breaking any bits. Admittedly I was using 45X magnification to align the board and was watching as the drill broke through, therefore I did not plunge the drills to half or more of their length.

Runout in such a design can come from at least four sources: 1) drill
being bent; 2) collet wobble; 3) bearing wobble; and 4) mount wobble.

I built one, too (and highly recommend the design if you can do it).

1) bent drills are unlikely in carbide
2) collets made from aluminum (dremel) are more likely to be deformed
and inaccurate, while hardened steel chucks or steel collets (example:
proxxon) are less likely to be deformed. I also suspect that proxxon
engineers to a higher standard.
3) ditto on the bearings
4) I used a linear table, one dimension, and relatively thick aluminum
(at least 1/4 inch) for support. I also used a linear stepper for the
drive, so it was not a factor (the table would have swamped any
variation).

Given that (and that the depth of penetration is settable), I've had
no problems with drill breaking.

>
>I seriously doubt that the problem people are having with drill breakage using Dremels is due simply to runout. I also don't doubt that they are having better results with other tools such as Proxxon rotary tools.
>

Yep. The mounts for the drills, if unsteady, and allowing sideways
movement while drilling, will also cause problems.

>The reason I mention this is that it would be difficult for the average person to improve the runout of tools such as the Dremel but if another cause for drill breakage was found perhaps that could be easily corrected.

Ancient fix for car problems: remove licence plates, replace
intervening material, replace licence plates.

I'd say that if the collets and chucks can't be improved, and
replacement of the tool is not desired, then I would concentrate on
the mount for wobble.

Harvey

>
>Craig

Re: drill pcb

2016-02-22 by craigl2@...

The real problem run out caused for me was the drill wandering before biting in and therefore being "off target". This was still a problem although less when I temporarily used a high-end spindle with a run out of less than .0005".

The runout is still present with the six dollar hobby RC motor I'm currently using but I found a way around the problem. Simply drilling through a .007' thick piece of cardboard helps somewhat but the drill would still wander off sometimes as much as .005".

The solution I found was to use a guide bushing positioned about .01" from the PCB. This results in the hole being drilled to .001" accuracy or better.

I am using a 1/8 inch thick piece of flat stock steel as the drill table. This provides three benefits:

1. Magnets hold the table to the frame so it can be quickly and easily removed for more open access to change the drill bits.

2. Two 3/8" X 3/8" neodymium magnets placed on top of the PCB allow it to be slid around for positioning but hold it (hands free) in place firmly for drilling. These may be a little stronger than necessary.

3. I made small bushings with a short 3/16" piece of steel drilled through with the appropriate size drill. These were pressed into a 1/8" thick plastic disk and four 1/8" X 1/8" neodymium magnets were pressed through 1/8" holes every 90 degrees. When I change to a different drill size I slip the appropriate size bushing down over the drill, replace the tabletop and slowly raise the drill until the magnets attach the bushing disk in perfect alignment to the underside of the table. Because there is still some runout of the drill there is a small countersunk area in the bushing facing the drill to guide it into the hole.

Craig

Re: drill pcb

2016-02-22 by bobledoux@...

I stand corrected. I did not get my drill press from harbor Freight.

This is the model I have:

http://www.jetsinc.com/index.php?main_page=product_info&products_id=1644

I purchased it four years ago.

It has a three speed pulley system. On ebay they go for $65 to $120 US. I see it for $75 with free shipping.

http://www.ebay.com/itm/MINI-DRILL-PRESS-COMPACT-DRILL-PRESSES-BENCH-JEWELER-HOBBY-3-SPEEDS-MAX-8500-RPM-/190586354986?hash=item2c5fd4fd2a:g:OHkAAOSwmUdUVnf7

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-22 by Michael Young

Aside from runout, feeds and speeds can be the culprit. FSWizard Pro gives the following for a 0.03" 2-flute, uncoated carbide drill in FR4.

RPM 20k
SFM 150 ft/min
Feed rate: 29 in/min

Torque and breaking torque are listed as equal.

In pure copper, RPM is 40k at roughly the same feed rate, for half the chip load. I don't have any thoughts on what this might mean for copper clad FR4.

Also check that the spindle mount is rigid and on axis with the feed. Strict perpendicularity to the work might not be so critically important, but can help reduce wander when starting the hole. A shorter bit is more gooderer, but they the bits seem to come in only one length.

I use a rotozip clamped to a linear guide. It develops 20k+ rpm and very seldom breaks bits. I attribute this mostly to the high RPM and the relatively rigid mount and guide. Any slop or flex in the mount is sure to cause problems. Hand held is definitely out of the question (I didn't read the entire thread, so maybe this isn't an issue).

Mike.

On 2/22/2016 11:33 AM, craigl2@... [Homebrew_PCBs] wrote:

The real problem run out caused for me was the drill wandering before biting in and therefore being "off target". This was still a problem although less when I temporarily used a high-end spindle with a run out of less than .0005".

The runout is still present with the six dollar hobby RC motor I'm currently using but I found a way around the problem. Simply drilling through a .007' thick piece of cardboard helps somewhat but the drill would still wander off sometimes as much as .005".

The solution I found was to use a guide bushing positioned about .01" from the PCB. This results in the hole being drilled to .001" accuracy or better.

I am using a 1/8 inch thick piece of flat stock steel as the drill table. This provides three benefits:

1. Magnets hold the table to the frame so it can be quickly and easily removed for more open access to change the drill bits.

2. Two 3/8" X 3/8" neodymium magnets placed on top of the PCB allow it to be slid around for positioning but hold it (hands free) in place firmly for drilling. These may be a little stronger than necessary.

3. I made small bushings with a short 3/16" piece of steel drilled through with the appropriate size drill. These were pressed into a 1/8" thick plastic disk and four 1/8" X 1/8" neodymium magnets were pressed through 1/8" holes every 90 degrees. When I change to a different drill size I slip the appropriate size bushing down over the drill, replace the tabletop and slowly raise the drill until the magnets attach the bushing disk in perfect alignment to the underside of the table. Because there is still some runout of the drill there is a small countersunk area in the bushing facing the drill to guide it into the hole.

Craig

RE: [Homebrew_PCBs] drill pcb

2016-02-23 by keith printy

Only problem I see with this besides the shipping cost to the united states is ,it requires 220 volts

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Sunday, February 21, 2016 4:09 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] drill pcb

hello to the group I wanted to know what would be a low cost-effective solution to drill pcb ? I had found this on ebay
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080

!

PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustabl...

PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080 in | eBay

View on www.ebay.it

Preview by Yahoo

Thank
Roberto

RE: [Homebrew_PCBs] Re: drill pcb

2016-02-23 by Jeff Heiss

This sounds interesting. Are there any pictures avaible?

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Monday, February 22, 2016 12:34 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] Re: drill pcb

The real problem run out caused for me was the drill wandering before biting in and therefore being "off target". This was still a problem although less when I temporarily used a high-end spindle with a run out of less than .0005".

The runout is still present with the six dollar hobby RC motor I'm currently using but I found a way around the problem. Simply drilling through a .007' thick piece of cardboard helps somewhat but the drill would still wander off sometimes as much as .005".

The solution I found was to use a guide bushing positioned about .01" from the PCB. This results in the hole being drilled to .001" accuracy or better.

I am using a 1/8 inch thick piece of flat stock steel as the drill table. This provides three benefits:

1. Magnets hold the table to the frame so it can be quickly and easily removed for more open access to change the drill bits.

2. Two 3/8" X 3/8" neodymium magnets placed on top of the PCB allow it to be slid around for positioning but hold it (hands free) in place firmly for drilling. These may be a little stronger than necessary.

3. I made small bushings with a short 3/16" piece of steel drilled through with the appropriate size drill. These were pressed into a 1/8" thick plastic disk and four 1/8" X 1/8" neodymium magnets were pressed through 1/8" holes every 90 degrees. When I change to a different drill size I slip the appropriate size bushing down over the drill, replace the tabletop and slowly raise the drill until the magnets attach the bushing disk in perfect alignment to the underside of the table. Because there is still some runout of the drill there is a small countersunk area in the bushing facing the drill to guide it into the hole.

Craig

RE: [Homebrew_PCBs] Re: drill pcb

2016-02-23 by craigl2@...

---In Homebrew_PCBs@yahoogroups.com, <jeff.heiss@...> wrote :

This sounds interesting. Are there any pictures avaible?

I do not currently have any photographs. I may be able to take some within the next few days. Are there any aspects of the drill you are particularly interested in?

Craig

Re: drill pcb

2016-02-23 by craigl2@...

A feed rate of 29 in./min. equates to drilling through a PCB in a little over 1/10 of a second. Are you really drilling through them this quickly?

Craig

---In Homebrew_PCBs@yahoogroups.com, <mikewhy@...> wrote :

Aside from runout, feeds and speeds can be the culprit. FSWizard Pro gives the following for a 0.03" 2-flute, uncoated carbide drill in FR4.

RPM 20k
SFM 150 ft/min
Feed rate: 29 in/min
........

Re: drill pcb

2016-02-23 by jim.strohm@...

International voltage converters are widely available in the states.

73
Jim N6OTQ

---In Homebrew_PCBs@yahoogroups.com, <keethpr@...> wrote :

Only problem I see with this besides the shipping cost to the united states is ,it requires 220 volts

RE: [Homebrew_PCBs] Re: drill pcb

2016-02-23 by mikewhy

Me personally, the 1/2" per second or so leaves a large margin even with bits already starting to dull. Someone else with a slower spindle might find the margin not nearly as large as intuition might suggest. Breaking torque was the limit in the FSWizard figures I gave. For 5000 rpm, a seemingly safe and slow feed of 1/8" per second exceeds the recommended feed rate of 7.05 in/min.

Mike.

-------- Original message --------

From: "craigl2@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>

Date: 2/23/2016 11:16 AM (GMT-06:00)

To: Homebrew_PCBs@yahoogroups.com

Subject: [Homebrew_PCBs] Re: drill pcb

A feed rate of 29 in./min. equates to drilling through a PCB in a little over 1/10 of a second. Are you really drilling through them this quickly?

Craig

---In Homebrew_PCBs@yahoogroups.com, <mikewhy@...> wrote :

Aside from runout, feeds and speeds can be the culprit. FSWizard Pro gives the following for a 0.03" 2-flute, uncoated carbide drill in FR4.

RPM 20k
SFM 150 ft/min
Feed rate: 29 in/min
........

Re: [Homebrew_PCBs] drill pcb

2016-02-23 by Roger Blair

FYI... 110V, USA.
http://www.ebay.com/itm/MINI-DRILL-PRESS-COMPACT-DRILL-PRESSES-BENCH-JEWELER-HOBBY-3-SPEEDS-MAX-8500-RPM/190586354986?_trksid=p4069.c100039.m2059&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20140107094819%26meid%3D8798deee68494a4f924698bb53d5a287%26pid%3D100039%26rk%3D3%26rkt%3D4%26mehot%3Dag%26sd%3D272029555215

Roger

On 2/22/2016 4:25 PM, 'keith printy' keethpr@... [Homebrew_PCBs] wrote:

Only problem I see with this besides the shipping cost to the united states is ,it requires 220 volts

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Sunday, February 21, 2016 4:09 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] drill pcb

hello to the group I wanted to know what would be a low cost-effective solution to drill pcb ? I had found this on ebay
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080

!

PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustabl...

PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080 in | eBay

View on www.ebay.it

Preview by Yahoo

Thank
Roberto

Re: [Homebrew_PCBs] drill pcb

2016-02-23 by Dennis Shelgren

Yea, just using the feeds and speeds calculator, I typically go as fast (rpms) as I can manage. Of course I have an air drill for pcbs. 56k rpms max.

On Feb 23, 2016 1:26 PM, "Roger Blair Roger.Blair@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> wrote:

FYI... 110V, USA.
http://www.ebay.com/itm/MINI-DRILL-PRESS-COMPACT-DRILL-PRESSES-BENCH-JEWELER-HOBBY-3-SPEEDS-MAX-8500-RPM/190586354986?_trksid=p4069.c100039.m2059&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20140107094819%26meid%3D8798deee68494a4f924698bb53d5a287%26pid%3D100039%26rk%3D3%26rkt%3D4%26mehot%3Dag%26sd%3D272029555215

Roger

On 2/22/2016 4:25 PM, 'keith printy' keethpr@... [Homebrew_PCBs] wrote:

Only problem I see with this besides the shipping cost to the united states is ,it requires 220 volts

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Sunday, February 21, 2016 4:09 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] drill pcb

hello to the group I wanted to know what would be a low cost-effective solution to drill pcb ? I had found this on ebay
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080

!

PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustabl...

PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080 in | eBay

View on www.ebay.it

Preview by Yahoo

Thank
Roberto

RE: [Homebrew_PCBs] drill pcb

2016-02-23 by Jeff Heiss

What kind of air drill? Those are some impressive RPMs.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, February 23, 2016 4:30 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] drill pcb

Yea, just using the feeds and speeds calculator, I typically go as fast (rpms) as I can manage. Of course I have an air drill for pcbs. 56k rpms max.

On Feb 23, 2016 1:26 PM, "Roger Blair Roger.Blair@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> wrote:

FYI... 110V, USA.
http://www.ebay.com/itm/MINI-DRILL-PRESS-COMPACT-DRILL-PRESSES-BENCH-JEWELER-HOBBY-3-SPEEDS-MAX-8500-RPM/190586354986?_trksid=p4069.c100039.m2059&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20140107094819%26meid%3D8798deee68494a4f924698bb53d5a287%26pid%3D100039%26rk%3D3%26rkt%3D4%26mehot%3Dag%26sd%3D272029555215

Roger

On 2/22/2016 4:25 PM, 'keith printy' keethpr@... [Homebrew_PCBs] wrote:

Only problem I see with this besides the shipping cost to the united states is ,it requires 220 volts

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Sunday, February 21, 2016 4:09 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] drill pcb

hello to the group I wanted to know what would be a low cost-effective solution to drill pcb ? I had found this on ebay
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080
!
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustabl...
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080 in | eBay
View on www.ebay.it
Preview by Yahoo

Thank
Roberto

RE: [Homebrew_PCBs] Re: drill pcb

2016-02-23 by Jeff Heiss

I’m intrigued by the interchangeable bushings. Maybe one of the bushings, or motor, linear slide or overall unit?

Jeff

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, February 23, 2016 12:07 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Re: drill pcb

---In Homebrew_PCBs@yahoogroups.com, <jeff.heiss@...> wrote :

This sounds interesting. Are there any pictures avaible?

I do not currently have any photographs. I may be able to take some within the next few days. Are there any aspects of the drill you are particularly interested in?

Craig

RE: [Homebrew_PCBs] Re: drill pcb

2016-02-24 by keith printy

Aren’t most of these converters to convert 220 down to 120 ?

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, February 23, 2016 12:35 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] Re: drill pcb

International voltage converters are widely available in the states.

73
Jim N6OTQ

---In Homebrew_PCBs@yahoogroups.com, <keethpr@...> wrote :

Only problem I see with this besides the shipping cost to the united states is ,it requires 220 volts

RE: [Homebrew_PCBs] drill pcb

2016-02-24 by Dennis Shelgren

Just a super cheap one from harbor freight. A much better option would be dental gear. Seriously, most dentists are also home machinists! You need at least 30k rpm for dental mills and old bits might be free! My dentist was super suprised I loved machining. We talked for an hour straight!

On Feb 23, 2016 1:40 PM, "'Jeff Heiss' jeff.heiss@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> wrote:

What kind of air drill? Those are some impressive RPMs.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, February 23, 2016 4:30 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] drill pcb

Yea, just using the feeds and speeds calculator, I typically go as fast (rpms) as I can manage. Of course I have an air drill for pcbs. 56k rpms max.
On Feb 23, 2016 1:26 PM, "Roger Blair Roger.Blair@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> wrote:

FYI... 110V, USA.
http://www.ebay.com/itm/MINI-DRILL-PRESS-COMPACT-DRILL-PRESSES-BENCH-JEWELER-HOBBY-3-SPEEDS-MAX-8500-RPM/190586354986?_trksid=p4069.c100039.m2059&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20140107094819%26meid%3D8798deee68494a4f924698bb53d5a287%26pid%3D100039%26rk%3D3%26rkt%3D4%26mehot%3Dag%26sd%3D272029555215

Roger
On 2/22/2016 4:25 PM, 'keith printy' keethpr@... [Homebrew_PCBs] wrote:

Only problem I see with this besides the shipping cost to the united states is ,it requires 220 volts

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Sunday, February 21, 2016 4:09 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] drill pcb

hello to the group I wanted to know what would be a low cost-effective solution to drill pcb ? I had found this on ebay
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080
!
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustabl...
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080 in | eBay
View on www.ebay.it
Preview by Yahoo

Thank
Roberto

Re: drill pcb

2016-02-24 by craigl2@...

I will try to get some photographs within the next few days (it's in the workshop area I have on the other side of town).

In the meantime this is the motor I am using:

http://www.robotshop.com/en/rs-550-motor-19300rpm-12v-6249oz-in.html

It draws about 1.1 amps with no load and 1.9 amps when drilling with a #65 drill. Using a current clamp on my Fluke multimeter, set to capture the minimum and maximum values, the start up current draw is about 7.6 amps. A 12 volt 4 amp power supply bought from the above source only causes the motor to stutter, a 12 volt 15 amp power supply from the above source works but only if the switch is on the correct side of the power supply (I believe I had it on the output side). The problem with both of these supplies appear to be due to protection circuitry and the initial start up draw. Currently I am using 12 volt 3.5 amp power supply from a Nintendo Game Cube which works well however, I'm a little concerned it may eventually fail due to the large initial power draw.

I think this is the same motor for a couple dollars cheaper:

http://www.goldmine-elec-products.com/prodinfo.asp?number=G21086

This is the chuck I am using:

http://www.amazon.com/Water-Brass-3-17mm-Motor-2-5mm-3-17mm/dp/B00NXSETD0/ref=sr_1_1?ie=UTF8&qid=1456280385&sr=8-1&keywords=Gold+Tone+Brass+3.17mm+1%2F8%22+Motor+Shaft

They are also available on eBay.

The motor shaft has about .00025" runout. There is about a .004" runout with the chuck as measured on the drill shaft. I am unclear why this is since it's a straight through .125" hole so there is no problem with concentricity as there would be trying to connect a motor with a different size shaft to a standard carbide PCB drill. My first attempt at making my own connector drilling and reaming a brass rod and using set screws was only slightly better with about .003" runout. In any case using the guide bushings makes this a nonissue.

I used a linear stage probably by Del-Tron but unmarked. Most of these are not meant to be used in a vertical position but so far it hasn't failed. If it does I will probably replace it with a small linear rail from eBay. Neither of these are cheap but you can find something suitable on eBay for 20-30 dollars, maybe less if you are not in a hurry. The cheaper linear rails likely have somewhat more friction but should still result in a very sensitive feel as long as they use ball bearings and not simple plastic slides. Although you may get by with 1/2" of travel 1" or so gives more leeway in construction. The finished drill press has a much more sensitive feel than my Cameron micro drill ( http://cameronmicrodrillpress.com/manual-micro-drill-presses/cameron-164-series/cameron-164/ ) or an Albrecht sensitive drill adapter used in a regular drill press.

Craig

---In Homebrew_PCBs@yahoogroups.com, <jeff.heiss@...> wrote :

I’m intrigued by the interchangeable bushings. Maybe one of the bushings, or motor, linear slide or overall unit?

Jeff

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, February 23, 2016 12:07 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Re: drill pcb

---In Homebrew_PCBs@yahoogroups.com, <jeff.heiss@...> wrote :

This sounds interesting. Are there any pictures avaible?

I do not currently have any photographs. I may be able to take some within the next few days. Are there any aspects of the drill you are particularly interested in?

Craig

RE: [Homebrew_PCBs] drill pcb

2016-02-24 by Jeff Heiss

Can standard 1/8” shank PCB drill bits fit in a dental drill? Are there adapters to fit them if not?

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, February 23, 2016 9:59 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] drill pcb

Just a super cheap one from harbor freight. A much better option would be dental gear. Seriously, most dentists are also home machinists! You need at least 30k rpm for dental mills and old bits might be free! My dentist was super suprised I loved machining. We talked for an hour straight!

On Feb 23, 2016 1:40 PM, "'Jeff Heiss' jeff.heiss@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> wrote:

What kind of air drill? Those are some impressive RPMs.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, February 23, 2016 4:30 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] drill pcb

Yea, just using the feeds and speeds calculator, I typically go as fast (rpms) as I can manage. Of course I have an air drill for pcbs. 56k rpms max.

On Feb 23, 2016 1:26 PM, "Roger Blair Roger.Blair@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> wrote:

FYI... 110V, USA.
http://www.ebay.com/itm/MINI-DRILL-PRESS-COMPACT-DRILL-PRESSES-BENCH-JEWELER-HOBBY-3-SPEEDS-MAX-8500-RPM/190586354986?_trksid=p4069.c100039.m2059&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20140107094819%26meid%3D8798deee68494a4f924698bb53d5a287%26pid%3D100039%26rk%3D3%26rkt%3D4%26mehot%3Dag%26sd%3D272029555215

Roger

On 2/22/2016 4:25 PM, 'keith printy' keethpr@... [Homebrew_PCBs] wrote:

Only problem I see with this besides the shipping cost to the united states is ,it requires 220 volts

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Sunday, February 21, 2016 4:09 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] drill pcb

hello to the group I wanted to know what would be a low cost-effective solution to drill pcb ? I had found this on ebay
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080
!
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustabl...
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080 in | eBay
View on www.ebay.it
Preview by Yahoo

Thank
Roberto

RE: [Homebrew_PCBs] drill pcb

2016-02-24 by Tony Smith

They’re about $30 or so, I’ve got mine clamped to a mini-mill. They work well. For the price they work very well.

If you do decide to clamp it to something do it at the ends, not the middle.

Tony

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Wednesday, 24 February 2016 1:59 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] drill pcb

Just a super cheap one from harbor freight. A much better option would be dental gear. Seriously, most dentists are also home machinists! You need at least 30k rpm for dental mills and old bits might be free! My dentist was super suprised I loved machining. We talked for an hour straight!

On Feb 23, 2016 1:40 PM, "'Jeff Heiss' jeff.heiss@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> wrote:

What kind of air drill? Those are some impressive RPMs.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, February 23, 2016 4:30 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] drill pcb

Yea, just using the feeds and speeds calculator, I typically go as fast (rpms) as I can manage. Of course I have an air drill for pcbs. 56k rpms max.

On Feb 23, 2016 1:26 PM, "Roger Blair Roger.Blair@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> wrote:

FYI... 110V, USA.
http://www.ebay.com/itm/MINI-DRILL-PRESS-COMPACT-DRILL-PRESSES-BENCH-JEWELER-HOBBY-3-SPEEDS-MAX-8500-RPM/190586354986?_trksid=p4069.c100039.m2059&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20140107094819%26meid%3D8798deee68494a4f924698bb53d5a287%26pid%3D100039%26rk%3D3%26rkt%3D4%26mehot%3Dag%26sd%3D272029555215

Roger

On 2/22/2016 4:25 PM, 'keith printy' keethpr@... [Homebrew_PCBs] wrote:

Only problem I see with this besides the shipping cost to the united states is ,it requires 220 volts

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Sunday, February 21, 2016 4:09 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] drill pcb

hello to the group I wanted to know what would be a low cost-effective solution to drill pcb ? I had found this on ebay
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080
!
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustabl...
PCB Art Mini Bench Drill Press 6mm Chuck Fully Adjustable Speed 100080 in | eBay
View on www.ebay.it
Preview by Yahoo

Thank
Roberto

RE: [Homebrew_PCBs] Re: drill pcb

2016-02-24 by jim.strohm@...

Depends. Most of them are autotransformers. In this case, the full winding is used for 220 and it's tapped halfway down for 110. I got my last two for free on CraigsList.

---In Homebrew_PCBs@yahoogroups.com, <keethpr@...> wrote :

Aren’t most of these converters to convert 220 down to 120 ?

International voltage converters are widely available in the states.

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-24 by rolohar@...

Not an "autotransformer"

You probably want to stay away from an "autotransformer" in this situation because of line isolation factors.

A simple "step down" of "step up transformer would be a safer choice, where there is a primary and

a secondary winding configuration.

Do your homework before delving into this transformer application.

Regards,

Roland F. Harriston, P.D.

***************************

From: "jim.strohm@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 9:29:25 AM
Subject: RE: [Homebrew_PCBs] Re: drill pcb

Depends. Most of them are autotransformers. In this case, the full winding is used for 220 and it's tapped halfway down for 110. I got my last two for free on CraigsList.

---In Homebrew_PCBs@yahoogroups.com, <keethpr@...> wrote :

Aren’t most of these converters to convert 220 down to 120 ?

International voltage converters are widely available in the states.

Re: drill pcb

2016-02-25 by craigl2@...

Since you would normally be plugging the drill into a 220 wall outlet directly how is plugging it into an autotransformer any less safe?

Craig

---In Homebrew_PCBs@yahoogroups.com, <rolohar@...> wrote :

Not an "autotransformer"

You probably want to stay away from an "autotransformer" in this situation because of line isolation factors.

A simple "step down" of "step up transformer would be a safer choice, where there is a primary and

a secondary winding configuration.

Do your homework before delving into this transformer application.

Regards,

Roland F. Harriston, P.D.

***************************

From: "jim.strohm@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 9:29:25 AM
Subject: RE: [Homebrew_PCBs] Re: drill pcb

Depends. Most of them are autotransformers. In this case, the full winding is used for 220 and it's tapped halfway down for 110. I got my last two for free on CraigsList.

---In Homebrew_PCBs@yahoogroups.com, <keethpr@...> wrote :

Aren’t most of these converters to convert 220 down to 120 ?

International voltage converters are widely available in the states.

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by rolohar@...

Perhaps I do not understand exactly how the autotransformer would be used with the tool you are

planning to use.

A "real" autotransformer has only one winding, therefore there is no isolation between the power source and the

tool you are using, so it is possible that the user could be exposed to the full power from the source.

Please explain how you plan to use the "autotransformer" in this application....which is (I believe) to

operate a 220 volt tool and a 120 volt power source.

Or, perhaps, the term "autotransformer" is not an accurate name of the device you want to use.

A step up or step down transformer would be cool.

Regards,

Roland

From: "craigl2@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 6:45:40 PM
Subject: [Homebrew_PCBs] Re: drill pcb

Since you would normally be plugging the drill into a 220 wall outlet directly how is plugging it into an autotransformer any less safe?

Craig

---In Homebrew_PCBs@yahoogroups.com, <rolohar@...> wrote :

Not an "autotransformer"

You probably want to stay away from an "autotransformer" in this situation because of line isolation factors.

A simple "step down" of "step up transformer would be a safer choice, where there is a primary and

a secondary winding configuration.

Do your homework before delving into this transformer application.

Regards,

Roland F. Harriston, P.D.

***************************

From: "jim.strohm@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 9:29:25 AM
Subject: RE: [Homebrew_PCBs] Re: drill pcb

Depends. Most of them are autotransformers. In this case, the full winding is used for 220 and it's tapped halfway down for 110. I got my last two for free on CraigsList.

---In Homebrew_PCBs@yahoogroups.com, <keethpr@...> wrote :

Aren’t most of these converters to convert 220 down to 120 ?

International voltage converters are widely available in the states.

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by Stefan Trethan

The point he makes, correctly, is that the tool does not need isolation since it is designed to operate directly on 220V anyway.

Many of the 220->110 and 110->220 converters sold are autotransformers.

ST

On Thu, Feb 25, 2016 at 2:57 AM, rolohar@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

Perhaps I do not understand exactly how the autotransformer would be used with the tool you are
planning to use.

A "real" autotransformer has only one winding, therefore there is no isolation between the power source and the
tool you are using, so it is possible that the user could be exposed to the full power from the source.

Please explain how you plan to use the "autotransformer" in this application....which is (I believe) to
operate a 220 volt tool and a 120 volt power source.

Or, perhaps, the term "autotransformer" is not an accurate name of the device you want to use.
A step up or step down transformer would be cool.

Regards,

Roland

From: "craigl2@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 6:45:40 PM
Subject: [Homebrew_PCBs] Re: drill pcb

Since you would normally be plugging the drill into a 220 wall outlet directly how is plugging it into an autotransformer any less safe?

Craig

---In Homebrew_PCBs@yahoogroups.com, <rolohar@...> wrote :

Not an "autotransformer"

You probably want to stay away from an "autotransformer" in this situation because of line isolation factors.

A simple "step down" of "step up transformer would be a safer choice, where there is a primary and
a secondary winding configuration.

Do your homework before delving into this transformer application.

Regards,

Roland F. Harriston, P.D.
***************************

From: "jim.strohm@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 9:29:25 AM
Subject: RE: [Homebrew_PCBs] Re: drill pcb

Depends. Most of them are autotransformers. In this case, the full winding is used for 220 and it's tapped halfway down for 110. I got my last two for free on CraigsList.

---In Homebrew_PCBs@yahoogroups.com, <keethpr@...> wrote :
Aren’t most of these converters to convert 220 down to 120 ?
International voltage converters are widely available in the states.

RE: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by keith printy

An autotransformer is similar to how a variac works. I have several of those here ,even some 220 volt ones you would need to make sure the switch is in the line that is 220 volts above the neutral

These can deliver up to 280 volts at full setting so one would need to be careful with not setting it too high

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Wednesday, February 24, 2016 8:58 PM
To: Homebrew PCBs
Subject: Re: [Homebrew_PCBs] Re: drill pcb

Perhaps I do not understand exactly how the autotransformer would be used with the tool you are

planning to use.

A "real" autotransformer has only one winding, therefore there is no isolation between the power source and the

tool you are using, so it is possible that the user could be exposed to the full power from the source.

Please explain how you plan to use the "autotransformer" in this application....which is (I believe) to

operate a 220 volt tool and a 120 volt power source.

Or, perhaps, the term "autotransformer" is not an accurate name of the device you want to use.

A step up or step down transformer would be cool.

Regards,

Roland

From: "craigl2@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 6:45:40 PM
Subject: [Homebrew_PCBs] Re: drill pcb

Since you would normally be plugging the drill into a 220 wall outlet directly how is plugging it into an autotransformer any less safe?

Craig

---In Homebrew_PCBs@yahoogroups.com, <rolohar@...> wrote :

Not an "autotransformer"

You probably want to stay away from an "autotransformer" in this situation because of line isolation factors.

A simple "step down" of "step up transformer would be a safer choice, where there is a primary and

a secondary winding configuration.

Do your homework before delving into this transformer application.

Regards,

Roland F. Harriston, P.D.

***************************

From: "jim.strohm@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 9:29:25 AM
Subject: RE: [Homebrew_PCBs] Re: drill pcb

Depends. Most of them are autotransformers. In this case, the full winding is used for 220 and it's tapped halfway down for 110. I got my last two for free on CraigsList.

---In Homebrew_PCBs@yahoogroups.com, <keethpr@...> wrote :

Aren’t most of these converters to convert 220 down to 120 ?

International voltage converters are widely available in the states.

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by rolohar@...

Disadvantages of an Autotransformer

The main disadvantage of an autotransformer is that it does not have the primary to secondary winding isolation of a conventional double wound transformer. Then autotransformer’s can not safely be used for stepping down higher voltages to much lower voltages suitable for smaller loads.
If the secondary side winding becomes open-circuited, current stops flowing through the primary winding stopping the transformer action resulting in the full primary voltage being applied to the secondary terminals.
If the secondary circuit suffers a short-circuit condition, the resulting primary current would be much larger than an equivalent double wound transformer due to the increased flux linkage damaging the autotransformer.
Since the neutral connection is common to both the primary and secondary windings, earthing of the secondary winding automatically Earth’s the primary as there is no isolation between the two windings. Double wound transformers are sometimes used to isolate equipment from earth.

From: "Stefan Trethan stefan_trethan@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 7:20:50 PM
Subject: Re: [Homebrew_PCBs] Re: drill pcb

The point he makes, correctly, is that the tool does not need isolation since it is designed to operate directly on 220V anyway.

Many of the 220->110 and 110->220 converters sold are autotransformers.

ST

On Thu, Feb 25, 2016 at 2:57 AM, rolohar@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

Perhaps I do not understand exactly how the autotransformer would be used with the tool you are
planning to use.

A "real" autotransformer has only one winding, therefore there is no isolation between the power source and the
tool you are using, so it is possible that the user could be exposed to the full power from the source.

Please explain how you plan to use the "autotransformer" in this application....which is (I believe) to
operate a 220 volt tool and a 120 volt power source.

Or, perhaps, the term "autotransformer" is not an accurate name of the device you want to use.
A step up or step down transformer would be cool.

Regards,

Roland

From: "craigl2@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 6:45:40 PM
Subject: [Homebrew_PCBs] Re: drill pcb

Since you would normally be plugging the drill into a 220 wall outlet directly how is plugging it into an autotransformer any less safe?

Craig

---In Homebrew_PCBs@yahoogroups.com, <rolohar@...> wrote :

Not an "autotransformer"

You probably want to stay away from an "autotransformer" in this situation because of line isolation factors.

A simple "step down" of "step up transformer would be a safer choice, where there is a primary and
a secondary winding configuration.

Do your homework before delving into this transformer application.

Regards,

Roland F. Harriston, P.D.
***************************

From: "jim.strohm@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 9:29:25 AM
Subject: RE: [Homebrew_PCBs] Re: drill pcb

Depends. Most of them are autotransformers. In this case, the full winding is used for 220 and it's tapped halfway down for 110. I got my last two for free on CraigsList.

---In Homebrew_PCBs@yahoogroups.com, <keethpr@...> wrote :
Aren’t most of these converters to convert 220 down to 120 ?
International voltage converters are widely available in the states.

RE: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by K5ESS

Autotransformer Rebuttal

“The main disadvantage of an autotransformer is that it does not have the primary to secondary winding isolation of a conventional double wound transformer.” Well it’s a disadvantage only if you need isolation. Where is the need for isolation to operate a 220v drill press via a step-up autotransformer from 110v?

“Then autotransformer’s can not safely be used for stepping down higher voltages to much lower voltages suitable for smaller loads.” Patently false. Variable autotransformers have been safely used for years to step down voltages. Any electrical device used incorrectly can be a safety hazard. When used properly an autotransformer is completely safe. One primary use for autotransformers is as a variable AC voltage source. Here are examples of commercial autotransformers versions of which have been used for years.

http://www.variac.com/staco_Variable_Transformer_Map.htm?gclid=CPKuw8b7kcsCFQctaQodlooPpQ

http://www.danaherspecialtyproducts.com/uploadedFiles/Siteroot/Superior_Electric/Products_and_Solutions/POWERSTAT%C2%AE_Variable_Transformers/powerstat%20cat.pdf

One use for small autotransformers “sometimes called Variacs (a tradename) is in the restoration of old radios. It is recommended that you connect the radio to a “Variac” and slowly bring up the applied voltage so as to not overstress the old components. The problem here is that some of these old radios have the chassis connected to one side of the AC line (mains to some non-US folks). This can result in a hazard if the power plug is inserted incorrectly leaving the radio chassis at line potential and a shocking hazard should you touch the chassis and a ground. This is an instance where an autotransformer doesn’t provide protective isolation if the radio is connected improperly.

“If the secondary side winding becomes open-circuited, current stops flowing through the primary winding stopping the transformer action resulting in the full primary voltage being applied to the secondary terminals.” Well in the case we’re talking about (an autotransformer that steps up the 110v line to 220v for the drill press) that would not result in any overvoltage damage since the “full primary voltage” of 110v would be applied to the 220v drill press. In addition, the remaining autotransformer winding would present a series inductance that would reduce the applied voltage by an amount determined by the load.

“If the secondary circuit suffers a short-circuit condition, the resulting primary current would be much larger than an equivalent double wound transformer due to the increased flux linkage damaging the autotransformer.” That’s why we use fuses. Transformers are generally very tolerant to overload so a short period of overload (before the fuse blows) is unlikely to damage it. Wellllll that assumes the autotransformer is fused which it should be.

Since the neutral connection is common to both the primary and secondary windings, earthing of the secondary winding automatically Earth’s the primary as there is no isolation between the two windings. Double wound transformers are sometimes used to isolate equipment from earth In the US power wiring has three connections, LINE, NEUTRAL, GROUND. I think most countries follow this standard now. It appears that the drill press in question has a three prong plug so that it adheres this standard. Any autotransformer used to power this drill press from US standard power should carry through all three connections, LINE, NEUTRAL, GROUND.

mnothdurft

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Wednesday, February 24, 2016 8:41 PM
To: Homebrew PCBs
Subject: Re: [Homebrew_PCBs] Re: drill pcb

Disadvantages of an Autotransformer

The main disadvantage of an autotransformer is that it does not have the primary to secondary winding isolation of a conventional double wound transformer. Then autotransformer’s can not safely be used for stepping down higher voltages to much lower voltages suitable for smaller loads.
If the secondary side winding becomes open-circuited, current stops flowing through the primary winding stopping the transformer action resulting in the full primary voltage being applied to the secondary terminals.
If the secondary circuit suffers a short-circuit condition, the resulting primary current would be much larger than an equivalent double wound transformer due to the increased flux linkage damaging the autotransformer.
Since the neutral connection is common to both the primary and secondary windings, earthing of the secondary winding automatically Earth’s the primary as there is no isolation between the two windings. Double wound transformers are sometimes used to isolate equipment from earth.

From: "Stefan Trethan stefan_trethan@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 7:20:50 PM
Subject: Re: [Homebrew_PCBs] Re: drill pcb

The point he makes, correctly, is that the tool does not need isolation since it is designed to operate directly on 220V anyway.

Many of the 220->110 and 110->220 converters sold are autotransformers.

ST

On Thu, Feb 25, 2016 at 2:57 AM, rolohar@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

Perhaps I do not understand exactly how the autotransformer would be used with the tool you are

planning to use.

A "real" autotransformer has only one winding, therefore there is no isolation between the power source and the

tool you are using, so it is possible that the user could be exposed to the full power from the source.

Please explain how you plan to use the "autotransformer" in this application....which is (I believe) to

operate a 220 volt tool and a 120 volt power source.

Or, perhaps, the term "autotransformer" is not an accurate name of the device you want to use.

A step up or step down transformer would be cool.

Regards,

Roland

From: "craigl2@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 6:45:40 PM
Subject: [Homebrew_PCBs] Re: drill pcb

Since you would normally be plugging the drill into a 220 wall outlet directly how is plugging it into an autotransformer any less safe?

Craig

---In Homebrew_PCBs@yahoogroups.com, <rolohar@...> wrote :

Not an "autotransformer"

You probably want to stay away from an "autotransformer" in this situation because of line isolation factors.

A simple "step down" of "step up transformer would be a safer choice, where there is a primary and

a secondary winding configuration.

Do your homework before delving into this transformer application.

Regards,

Roland F. Harriston, P.D.

***************************

From: "jim.strohm@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 9:29:25 AM
Subject: RE: [Homebrew_PCBs] Re: drill pcb

Depends. Most of them are autotransformers. In this case, the full winding is used for 220 and it's tapped halfway down for 110. I got my last two for free on CraigsList.

---In Homebrew_PCBs@yahoogroups.com, <keethpr@...> wrote :

Aren’t most of these converters to convert 220 down to 120 ?

International voltage converters are widely available in the states.

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by rolohar@...

YOU ALWAYS NEED "SAFETY" WHEN WORKING WITH POWER LINE ELECTRICITY!

TV "cheater cords" once used in repairing TV sets were known as "Suicide Cords" because the defeated the

isolation between the TV set and the power outlet.

Autotransformers and Variacs are often referred to as "Widow Makers" because they also do not isolate the

user from being exposed to the full potential of the voltage source.......be it 120 or 220 or whatever.

Mark My Words!

Get a step-up or step-down transformer that has the primary winding completely isolated from the

secondary winding and works on the concept of INDUCTION rather that direct hard wired connection

to whatever power source you are using.

Regards,

RFH

From: "'K5ESS' k5ess.nothdurft@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 9:41:55 PM
Subject: RE: [Homebrew_PCBs] Re: drill pcb

Autotransformer Rebuttal

“The main disadvantage of an autotransformer is that it does not have the primary to secondary winding isolation of a conventional double wound transformer.” Well it’s a disadvantage only if you need isolation. Where is the need for isolation to operate a 220v drill press via a step-up autotransformer from 110v?

“Then autotransformer’s can not safely be used for stepping down higher voltages to much lower voltages suitable for smaller loads.” Patently false. Variable autotransformers have been safely used for years to step down voltages. Any electrical device used incorrectly can be a safety hazard. When used properly an autotransformer is completely safe. One primary use for autotransformers is as a variable AC voltage source. Here are examples of commercial autotransformers versions of which have been used for years.

http://www.variac.com/staco_Variable_Transformer_Map.htm?gclid=CPKuw8b7kcsCFQctaQodlooPpQ

http://www.danaherspecialtyproducts.com/uploadedFiles/Siteroot/Superior_Electric/Products_and_Solutions/POWERSTAT%C2%AE_Variable_Transformers/powerstat%20cat.pdf

One use for small autotransformers “sometimes called Variacs (a tradename) is in the restoration of old radios. It is recommended that you connect the radio to a “Variac” and slowly bring up the applied voltage so as to not overstress the old components. The problem here is that some of these old radios have the chassis connected to one side of the AC line (mains to some non-US folks). This can result in a hazard if the power plug is inserted incorrectly leaving the radio chassis at line potential and a shocking hazard should you touch the chassis and a ground. This is an instance where an autotransformer doesn’t provide protective isolation if the radio is connected improperly.

“If the secondary side winding becomes open-circuited, current stops flowing through the primary winding stopping the transformer action resulting in the full primary voltage being applied to the secondary terminals.” Well in the case we’re talking about (an autotransformer that steps up the 110v line to 220v for the drill press) that would not result in any overvoltage damage since the “full primary voltage” of 110v would be applied to the 220v drill press. In addition, the remaining autotransformer winding would present a series inductance that would reduce the applied voltage by an amount determined by the load.

“If the secondary circuit suffers a short-circuit condition, the resulting primary current would be much larger than an equivalent double wound transformer due to the increased flux linkage damaging the autotransformer.” That’s why we use fuses. Transformers are generally very tolerant to overload so a short period of overload (before the fuse blows) is unlikely to damage it. Wellllll that assumes the autotransformer is fused which it should be.

Since the neutral connection is common to both the primary and secondary windings, earthing of the secondary winding automatically Earth’s the primary as there is no isolation between the two windings. Double wound transformers are sometimes used to isolate equipment from earth In the US power wiring has three connections, LINE, NEUTRAL, GROUND. I think most countries follow this standard now. It appears that the drill press in question has a three prong plug so that it adheres this standard. Any autotransformer used to power this drill press from US standard power should carry through all three connections, LINE, NEUTRAL, GROUND.

mnothdurft

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Wednesday, February 24, 2016 8:41 PM
To: Homebrew PCBs
Subject: Re: [Homebrew_PCBs] Re: drill pcb

Disadvantages of an Autotransformer

The main disadvantage of an autotransformer is that it does not have the primary to secondary winding isolation of a conventional double wound transformer. Then autotransformer’s can not safely be used for stepping down higher voltages to much lower voltages suitable for smaller loads.
If the secondary side winding becomes open-circuited, current stops flowing through the primary winding stopping the transformer action resulting in the full primary voltage being applied to the secondary terminals.
If the secondary circuit suffers a short-circuit condition, the resulting primary current would be much larger than an equivalent double wound transformer due to the increased flux linkage damaging the autotransformer.
Since the neutral connection is common to both the primary and secondary windings, earthing of the secondary winding automatically Earth’s the primary as there is no isolation between the two windings. Double wound transformers are sometimes used to isolate equipment from earth.

From: "Stefan Trethan stefan_trethan@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 7:20:50 PM
Subject: Re: [Homebrew_PCBs] Re: drill pcb

The point he makes, correctly, is that the tool does not need isolation since it is designed to operate directly on 220V anyway.

Many of the 220->110 and 110->220 converters sold are autotransformers.

ST

On Thu, Feb 25, 2016 at 2:57 AM, rolohar@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

Perhaps I do not understand exactly how the autotransformer would be used with the tool you are

planning to use.

A "real" autotransformer has only one winding, therefore there is no isolation between the power source and the

tool you are using, so it is possible that the user could be exposed to the full power from the source.

Please explain how you plan to use the "autotransformer" in this application....which is (I believe) to

operate a 220 volt tool and a 120 volt power source.

Or, perhaps, the term "autotransformer" is not an accurate name of the device you want to use.

A step up or step down transformer would be cool.

Regards,

Roland

From: "craigl2@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 6:45:40 PM
Subject: [Homebrew_PCBs] Re: drill pcb

Since you would normally be plugging the drill into a 220 wall outlet directly how is plugging it into an autotransformer any less safe?

Craig

---In Homebrew_PCBs@yahoogroups.com, <rolohar@...> wrote :

Not an "autotransformer"

You probably want to stay away from an "autotransformer" in this situation because of line isolation factors.

A simple "step down" of "step up transformer would be a safer choice, where there is a primary and

a secondary winding configuration.

Do your homework before delving into this transformer application.

Regards,

Roland F. Harriston, P.D.

***************************

From: "jim.strohm@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 9:29:25 AM
Subject: RE: [Homebrew_PCBs] Re: drill pcb

Depends. Most of them are autotransformers. In this case, the full winding is used for 220 and it's tapped halfway down for 110. I got my last two for free on CraigsList.

---In Homebrew_PCBs@yahoogroups.com, <keethpr@...> wrote :

Aren’t most of these converters to convert 220 down to 120 ?

International voltage converters are widely available in the states.

Re: drill pcb

2016-02-25 by craigl2@...

They also make 110 V to 110 V isolation transformers. You could buy a bunch and plug them into all the outlets in your house instead of plugging anything directly into the outlet. Just for "safety"…

Craig

---In Homebrew_PCBs@yahoogroups.com, <rolohar@...> wrote :

YOU ALWAYS NEED "SAFETY" WHEN WORKING WITH POWER LINE ELECTRICITY!

TV "cheater cords" once used in repairing TV sets were known as "Suicide Cords" because the defeated the

isolation between the TV set and the power outlet.

Autotransformers and Variacs are often referred to as "Widow Makers" because they also do not isolate the

user from being exposed to the full potential of the voltage source.......be it 120 or 220 or whatever.

Mark My Words!

Get a step-up or step-down transformer that has the primary winding completely isolated from the

secondary winding and works on the concept of INDUCTION rather that direct hard wired connection

to whatever power source you are using.

Regards,

RFH

RE: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by Andrew Volk

I wonder if your added runout is due to the hole being not EXACTLY 0.125”, or one or both of the shafts being a smidge small. Also, if you use set screws only on one side, you may distort the coupler enough for 0.004” runout. Collets, after all, go to a lot of trouble to grip the drill shaft on all sides equally.

Andy

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, February 23, 2016 8:03 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] Re: drill pcb

I will try to get some photographs within the next few days (it's in the workshop area I have on the other side of town).

In the meantime this is the motor I am using:

http://www.robotshop.com/en/rs-550-motor-19300rpm-12v-6249oz-in.html

It draws about 1.1 amps with no load and 1.9 amps when drilling with a #65 drill. Using a current clamp on my Fluke multimeter, set to capture the minimum and maximum values, the start up current draw is about 7.6 amps. A 12 volt 4 amp power supply bought from the above source only causes the motor to stutter, a 12 volt 15 amp power supply from the above source works but only if the switch is on the correct side of the power supply (I believe I had it on the output side). The problem with both of these supplies appear to be due to protection circuitry and the initial start up draw. Currently I am using 12 volt 3.5 amp power supply from a Nintendo Game Cube which works well however, I'm a little concerned it may eventually fail due to the large initial power draw.

I think this is the same motor for a couple dollars cheaper:

http://www.goldmine-elec-products.com/prodinfo.asp?number=G21086

This is the chuck I am using:

http://www.amazon.com/Water-Brass-3-17mm-Motor-2-5mm-3-17mm/dp/B00NXSETD0/ref=sr_1_1?ie=UTF8&qid=1456280385&sr=8-1&keywords=Gold+Tone+Brass+3.17mm+1%2F8%22+Motor+Shaft

They are also available on eBay.

The motor shaft has about .00025" runout. There is about a .004" runout with the chuck as measured on the drill shaft. I am unclear why this is since it's a straight through .125" hole so there is no problem with concentricity as there would be trying to connect a motor with a different size shaft to a standard carbide PCB drill. My first attempt at making my own connector drilling and reaming a brass rod and using set screws was only slightly better with about .003" runout. In any case using the guide bushings makes this a nonissue.

I used a linear stage probably by Del-Tron but unmarked. Most of these are not meant to be used in a vertical position but so far it hasn't failed. If it does I will probably replace it with a small linear rail from eBay. Neither of these are cheap but you can find something suitable on eBay for 20-30 dollars, maybe less if you are not in a hurry. The cheaper linear rails likely have somewhat more friction but should still result in a very sensitive feel as long as they use ball bearings and not simple plastic slides. Although you may get by with 1/2" of travel 1" or so gives more leeway in construction. The finished drill press has a much more sensitive feel than my Cameron micro drill ( http://cameronmicrodrillpress.com/manual-micro-drill-presses/cameron-164-series/cameron-164/ ) or an Albrecht sensitive drill adapter used in a regular drill press.

Craig

---In Homebrew_PCBs@yahoogroups.com, <jeff.heiss@...> wrote :

I’m intrigued by the interchangeable bushings. Maybe one of the bushings, or motor, linear slide or overall unit?

Jeff

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, February 23, 2016 12:07 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Re: drill pcb

---In Homebrew_PCBs@yahoogroups.com, <jeff.heiss@...> wrote :

This sounds interesting. Are there any pictures avaible?

I do not currently have any photographs. I may be able to take some within the next few days. Are there any aspects of the drill you are particularly interested in?

Craig

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by Stefan Trethan

You know just enough to be dangerous.

None of your statements are correct.

Cheater cords are not dangerous because they defeat the isolation between the TV and power outlet - there is no isolation between the TV and power outlet. They are dangerous for other reasons (chiefly miswiring).

Autotransformers and variacs are not generally referred to as widowmakers any more than all tree limbs are referred to as widowmakers. The proposed use here is safe and in compliance with the relevant standards.

You are dealing with lethal voltages at the output, no matter if it is ground referenced or not.

ST

On Thu, Feb 25, 2016 at 6:30 AM, rolohar@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

YOU ALWAYS NEED "SAFETY" WHEN WORKING WITH POWER LINE ELECTRICITY!

TV "cheater cords" once used in repairing TV sets were known as "Suicide Cords" because the defeated the
isolation between the TV set and the power outlet.

Autotransformers and Variacs are often referred to as "Widow Makers" because they also do not isolate the
user from being exposed to the full potential of the voltage source.......be it 120 or 220 or whatever.

Mark My Words!

Get a step-up or step-down transformer that has the primary winding completely isolated from the
secondary winding and works on the concept of INDUCTION rather that direct hard wired connection
to whatever power source you are using.

Regards,

RFH

RE: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by K5ESS

Another Rebuttal

YOU ALWAYS NEED "SAFETY" WHEN WORKING WITH POWER LINE ELECTRICITY!

OK!!!!!

TV "cheater cords" once used in repairing TV sets were known as "Suicide Cords" because the defeated the

isolation between the TV set and the power outlet. How did they defeat the isolation between the TV set and the power outlet? Old TVs had their power cords physically attached to the rear cover, preventing a means to service the set without another means to power the set. Cheater cords provided a way to power the TVs with the rear cover removed and had nothing to do with isolation between the TV and the power outlet.

Autotransformers and Variacs are often referred to as "Widow Makers" because they also do not isolate the

user from being exposed to the full potential of the voltage source.......be it 120 or 220 or whatever. So what “protects” the user from being exposed to the full potential of the voltage source in the absence of an autotransformer? As I stated “Any electrical device used incorrectly can be a safety hazard. When used properly an autotransformer is completely safe.”

mnothdurft

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Wednesday, February 24, 2016 11:30 PM
To: Homebrew PCBs
Subject: Re: [Homebrew_PCBs] Re: drill pcb

YOU ALWAYS NEED "SAFETY" WHEN WORKING WITH POWER LINE ELECTRICITY!

TV "cheater cords" once used in repairing TV sets were known as "Suicide Cords" because the defeated the

isolation between the TV set and the power outlet.

Autotransformers and Variacs are often referred to as "Widow Makers" because they also do not isolate the

user from being exposed to the full potential of the voltage source.......be it 120 or 220 or whatever.

Mark My Words!

Get a step-up or step-down transformer that has the primary winding completely isolated from the

secondary winding and works on the concept of INDUCTION rather that direct hard wired connection

to whatever power source you are using.

Regards,

RFH

From: "'K5ESS' k5ess.nothdurft@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 9:41:55 PM
Subject: RE: [Homebrew_PCBs] Re: drill pcb

Autotransformer Rebuttal

“The main disadvantage of an autotransformer is that it does not have the primary to secondary winding isolation of a conventional double wound transformer.” Well it’s a disadvantage only if you need isolation. Where is the need for isolation to operate a 220v drill press via a step-up autotransformer from 110v?

“Then autotransformer’s can not safely be used for stepping down higher voltages to much lower voltages suitable for smaller loads.” Patently false. Variable autotransformers have been safely used for years to step down voltages. Any electrical device used incorrectly can be a safety hazard. When used properly an autotransformer is completely safe. One primary use for autotransformers is as a variable AC voltage source. Here are examples of commercial autotransformers versions of which have been used for years.

http://www.variac.com/staco_Variable_Transformer_Map.htm?gclid=CPKuw8b7kcsCFQctaQodlooPpQ

http://www.danaherspecialtyproducts.com/uploadedFiles/Siteroot/Superior_Electric/Products_and_Solutions/POWERSTAT%C2%AE_Variable_Transformers/powerstat%20cat.pdf

One use for small autotransformers “sometimes called Variacs (a tradename) is in the restoration of old radios. It is recommended that you connect the radio to a “Variac” and slowly bring up the applied voltage so as to not overstress the old components. The problem here is that some of these old radios have the chassis connected to one side of the AC line (mains to some non-US folks). This can result in a hazard if the power plug is inserted incorrectly leaving the radio chassis at line potential and a shocking hazard should you touch the chassis and a ground. This is an instance where an autotransformer doesn’t provide protective isolation if the radio is connected improperly.

“If the secondary side winding becomes open-circuited, current stops flowing through the primary winding stopping the transformer action resulting in the full primary voltage being applied to the secondary terminals.” Well in the case we’re talking about (an autotransformer that steps up the 110v line to 220v for the drill press) that would not result in any overvoltage damage since the “full primary voltage” of 110v would be applied to the 220v drill press. In addition, the remaining autotransformer winding would present a series inductance that would reduce the applied voltage by an amount determined by the load.

“If the secondary circuit suffers a short-circuit condition, the resulting primary current would be much larger than an equivalent double wound transformer due to the increased flux linkage damaging the autotransformer.” That’s why we use fuses. Transformers are generally very tolerant to overload so a short period of overload (before the fuse blows) is unlikely to damage it. Wellllll that assumes the autotransformer is fused which it should be.

Since the neutral connection is common to both the primary and secondary windings, earthing of the secondary winding automatically Earth’s the primary as there is no isolation between the two windings. Double wound transformers are sometimes used to isolate equipment from earth In the US power wiring has three connections, LINE, NEUTRAL, GROUND. I think most countries follow this standard now. It appears that the drill press in question has a three prong plug so that it adheres this standard. Any autotransformer used to power this drill press from US standard power should carry through all three connections, LINE, NEUTRAL, GROUND.

mnothdurft

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Wednesday, February 24, 2016 8:41 PM
To: Homebrew PCBs
Subject: Re: [Homebrew_PCBs] Re: drill pcb

Disadvantages of an Autotransformer

The main disadvantage of an autotransformer is that it does not have the primary to secondary winding isolation of a conventional double wound transformer. Then autotransformer’s can not safely be used for stepping down higher voltages to much lower voltages suitable for smaller loads.
If the secondary side winding becomes open-circuited, current stops flowing through the primary winding stopping the transformer action resulting in the full primary voltage being applied to the secondary terminals.
If the secondary circuit suffers a short-circuit condition, the resulting primary current would be much larger than an equivalent double wound transformer due to the increased flux linkage damaging the autotransformer.
Since the neutral connection is common to both the primary and secondary windings, earthing of the secondary winding automatically Earth’s the primary as there is no isolation between the two windings. Double wound transformers are sometimes used to isolate equipment from earth.

From: "Stefan Trethan stefan_trethan@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 7:20:50 PM
Subject: Re: [Homebrew_PCBs] Re: drill pcb

The point he makes, correctly, is that the tool does not need isolation since it is designed to operate directly on 220V anyway.

Many of the 220->110 and 110->220 converters sold are autotransformers.

ST

On Thu, Feb 25, 2016 at 2:57 AM, rolohar@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

Perhaps I do not understand exactly how the autotransformer would be used with the tool you are

planning to use.

A "real" autotransformer has only one winding, therefore there is no isolation between the power source and the

tool you are using, so it is possible that the user could be exposed to the full power from the source.

Please explain how you plan to use the "autotransformer" in this application....which is (I believe) to

operate a 220 volt tool and a 120 volt power source.

Or, perhaps, the term "autotransformer" is not an accurate name of the device you want to use.

A step up or step down transformer would be cool.

Regards,

Roland

From: "craigl2@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 6:45:40 PM
Subject: [Homebrew_PCBs] Re: drill pcb

Since you would normally be plugging the drill into a 220 wall outlet directly how is plugging it into an autotransformer any less safe?

Craig

---In Homebrew_PCBs@yahoogroups.com, <rolohar@...> wrote :

Not an "autotransformer"

You probably want to stay away from an "autotransformer" in this situation because of line isolation factors.

A simple "step down" of "step up transformer would be a safer choice, where there is a primary and

a secondary winding configuration.

Do your homework before delving into this transformer application.

Regards,

Roland F. Harriston, P.D.

***************************

From: "jim.strohm@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 24, 2016 9:29:25 AM
Subject: RE: [Homebrew_PCBs] Re: drill pcb

Depends. Most of them are autotransformers. In this case, the full winding is used for 220 and it's tapped halfway down for 110. I got my last two for free on CraigsList.

---In Homebrew_PCBs@yahoogroups.com, <keethpr@...> wrote :

Aren’t most of these converters to convert 220 down to 120 ?

International voltage converters are widely available in the states.

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by Cecil Bayona

Don't ever get in a car, about 50,000 people a year die in automobiles, let's all be safe, we need the government to protect us from life..

On 2/24/2016 11:43 PM, craigl2@... [Homebrew_PCBs] wrote:

They also make 110 V to 110 V isolation transformers. You could buy a bunch and plug them into all the outlets in your house instead of plugging anything directly into the outlet. Just for "safety"…

Craig

---In Homebrew_PCBs@yahoogroups.com, <rolohar@...> wrote :

YOU ALWAYS NEED "SAFETY" WHEN WORKING WITH POWER LINE ELECTRICITY!

TV "cheater cords" once used in repairing TV sets were known as "Suicide Cords" because the defeated the

isolation between the TV set and the power outlet.

Autotransformers and Variacs are often referred to as "Widow Makers" because they also do not isolate the

user from being exposed to the full potential of the voltage source.......be it 120 or 220 or whatever.

Mark My Words!

Get a step-up or step-down transformer that has the primary winding completely isolated from the

secondary winding and works on the concept of INDUCTION rather that direct hard wired connection

to whatever power source you are using.

Regards,

RFH

-- Cecil - k5nwa http://thepartsplace.k5nwa.com/

Re: drill pcb

2016-02-25 by craigl2@...

All good points.

I have a Mitutoyo digital micrometer which measures to .00005" but, I have difficulty in getting repeatable measurements to less than .0002–3" accuracy. The motor shaft seems to measure .1248" sometimes and .1250" at other times. It is only about .33" long but as near as I can tell there is no taper or out of roundness. I did not think to measure the drill shanks as they are standard 1/8" carbide PCB drills.

Although I used a .124" reamer followed by a .125" reamer the hole is somewhat larger than .125" , a .1250" gage pin fits in, a .1255" pin does not (both are + or "go" types). The coupling was made of brass, I am thinking of trying to make another out of steel and lapping it to size.

Set screws can be used to hold something in very a precise position as evidenced by end mill holders, but possibly not with a coupling of this diameter / wall thickness.

Craig

---In Homebrew_PCBs@yahoogroups.com, <amvweb@...> wrote :

I wonder if your added runout is due to the hole being not EXACTLY 0.125”, or one or both of the shafts being a smidge small. Also, if you use set screws only on one side, you may distort the coupler enough for 0.004” runout. Collets, after all, go to a lot of trouble to grip the drill shaft on all sides equally.

Andy

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by symons391@...

I hope this helps for those not familiar with transformer terminology.

The most common type of transformer has a winding for the mains & the output voltages are separate windings or separate windings with various taps on those windings.

That gives isolation between the mains & the output voltages.

An Autotransformer has a single winding.

One end of the winding is a common for the mains & the output for the neutral or cold connection.

For it to be a step up transformer then the other mains connection (active or hot) is a tap part way up the winding & the output voltage is at the far end.

For a step down transformer, one end of the winding is still a common for the mains but the the output is the tap part way along while the other mains connection (active or hot) is at the far end of the winding.

Autotransformers are cheaper to produce because they use less winding ie copper & possibly less iron as well.

Autotransformers have two disadvantages.

1. There is no isolation between the mains input & the output because they share the winding.

2. If there is winding fault then the output can be directly connected to the mains input & receive the mains voltage.

If the autotransformer is stepping the voltage up then the output device will be running on a lower voltage but if the autotransformer is stepping the voltage down then the output will get over voltage. The fault may be a winding failure but even just a bad screw connection or a broken wire. An example of the major problems this can cause is if a non-USA person is using an autotransformer stepping down 220V or 240V to 110V for a USA appliance then the failure will cause the 110V appliance to cop the full 220V or 240V & this may even spectacularly destroy it.

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by Harvey White

On Thu, 25 Feb 2016 07:08:17 +0100, you wrote:

>You know just enough to be dangerous.
>None of your statements are correct.
>
>Cheater cords are not dangerous because they defeat the isolation between
>the TV and power outlet - there is no isolation between the TV and power
>outlet. They are dangerous for other reasons (chiefly miswiring).

It used to be that to get power to a radio (the all American 5) one
side of the AC line was connected directly to the chassis, and the
other side was rectified to produce power. The plastic knobs and case
were used to protect the user from the AC line. The particular
difficulty with this design is that the original cable could be
plugged in backwards. The radio would work, but the chassis was now
sitting at full line potential.

Any television so wired (and there were some) would suffer from the
same difficulty. I once modified a small color TV to be a monitor.
Unfortunately, it had the same kind of power supply and required an
isolation transformer to be used safely because the chassis was now
directly exposed.

In measuring equipment, typically oscilloscopes, the chassis is
connected to the AC ground pin. Thus the probe ground is equivalent
to the safety ground at the wall. This prohibits using the scope in a
"floating" mode where the ground/chassis would be at an elevated
potential.

Some people simply cut the ground pin on the scope power cord in an
effort to permit this kind of measurement. That results in the
metallic chassis of the scope being at elevated potentials. There's
also the problem when the device being measured has a fault that can
elevate its chassis above ground. There are some scopes where the
chassis is isolated and the scope is battery powered. These are
specifically made for such kinds of measurements (Tektronix 200
series).

The isolation transformer would help run the device in this situation
and prevent possible difficulties. In fact, there is a piece of test
equipment that combines an isolation transformer with a variac, and
has metering to detect leakage to ground in the device plugged in.
This is not a common piece of equipment, though.

As a note, the back of the TV set used to have the power cable
attached directly. Remove the back of the TV and the power cable was
disconnected. A cheater cord was this power cable that did not have a
back attached.

Harvey

>
>Autotransformers and variacs are not generally referred to as widowmakers
>any more than all tree limbs are referred to as widowmakers. The proposed
>use here is safe and in compliance with the relevant standards.
>
>You are dealing with lethal voltages at the output, no matter if it is
>ground referenced or not.
>
>
>
>ST
>
>On Thu, Feb 25, 2016 at 6:30 AM, rolohar@... [Homebrew_PCBs] <
>Homebrew_PCBs@yahoogroups.com> wrote:
>
>>
>>
>> YOU ALWAYS NEED "SAFETY" WHEN WORKING WITH POWER LINE ELECTRICITY!
>>
>> TV "cheater cords" once used in repairing TV sets were known as "Suicide
>> Cords" because the defeated the
>> isolation between the TV set and the power outlet.
>>
>> Autotransformers and Variacs are often referred to as "Widow Makers"
>> because they also do not isolate the
>> user from being exposed to the full potential of the voltage
>> source.......be it 120 or 220 or whatever.
>>
>> Mark My Words!
>>
>> Get a step-up or step-down transformer that has the primary winding
>> completely isolated from the
>> secondary winding and works on the concept of INDUCTION rather that direct
>> hard wired connection
>> to whatever power source you are using.
>>
>> Regards,
>>
>> RFH
>>
>>

Re: drill pcb

2016-02-25 by jim.strohm@...

Roland, let's say (for instance) that you had a 220V device that you plugged directly into a Euro 220V outlet.
Then let's say you had a comparable 110V device that you plugged into a 110V American outlet.
What would be the difference in isolation between the two? Now let's say you were to use an autotransformer to use the 110V device on the 220V outlet, and (after disconnecting, of course) used the autotransformer to use the 220V device on the 110V outlet?

Assuming no exposed mains wiring, what would be the isolation differences between those four cases?

73
Jim N6OTQ

---In Homebrew_PCBs@yahoogroups.com, <rolohar@...> wrote :

Not an "autotransformer"

You probably want to stay away from an "autotransformer" in this situation because of line isolation factors.

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by rolohar@...

A "cheater cord" was (is) dangerous because it allowed a person access to the TV chassis when the back of the

TV set was removed. The original power cord on the TV set was configured so that if the back of the TV was

removed, the power cord came off with the back of the TV set. The "back" of TV sets in those days was

usually made of some non-conductive material like fiberboard or other paper-based material, to

ISOLATE the user from the voltage potential of the chassis.

The power cord was permanantly anchored to this back, so that it was not possible (normally) to remove the back

without disconnecting the power cord.

TV repair men made "cheater" cords that would allow them to power up the TV set with the back removed.

They lovingly named these cheater cords "suicide cords" because they allowed the repairman to be

exposed to the live, powered-on TV chassis, and if he was not careful, he could do damage to himself.

Variacs and autotransformers only have one winding. There is no primary/secondary winding

configuration. There is no iron core to facilitate induction between the primary and the secondary

windings. Autotransformers and Variacs and Rheostats were lovingly referred to as "Widow Makers"

for the same reason..............the user is not isolated from the power source as in a "regular"

transformer. An Isolation transformer generally performs NO step up or step down function.

It merely ISOLATES the user and the circuitry from the power line.

Four or five minutes spent reading any of the literature on Variacs (a trade name, actually) and

auto transformers (which really are not "transformers" in the true technical sense) will reveal the

precautions that must be observed when employing these devices.

There are many, many appliances made that will allow one to use 220 volt equipment on 110 volt

sources, and vice-versa. These devices are constructed in such a way as to isolate the user

(and whatever is plugged into them) with complete isolation from the power source. The are

often simply called "Converters". There are probably many circuit configurations that are used

in these devices.

There are also very elaborate "converter boxes" that are used in more sophisticated applications.

Some have metering and monitoring features, and be the type of device that would be applicable

to machine tools, etc.

Please review the definitions of:

Variac

Autotransformer

Rheostat

Step-Up and Step-Down TRANSFORMERS!

Isolation TRANSFORMER

Inductance

Be Careful,

Roland F. Harriston, P.D.

***************************

From: "Harvey White madyn@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Thursday, February 25, 2016 6:24:49 AM
Subject: Re: [Homebrew_PCBs] Re: drill pcb

On Thu, 25 Feb 2016 07:08:17 +0100, you wrote:

>You know just enough to be dangerous.
>None of your statements are correct.
>
>Cheater cords are not dangerous because they defeat the isolation between
>the TV and power outlet - there is no isolation between the TV and power
>outlet. They are dangerous for other reasons (chiefly miswiring).

It used to be that to get power to a radio (the all American 5) one
side of the AC line was connected directly to the chassis, and the
other side was rectified to produce power. The plastic knobs and case
were used to protect the user from the AC line. The particular
difficulty with this design is that the original cable could be
plugged in backwards. The radio would work, but the chassis was now
sitting at full line potential.

Any television so wired (and there were some) would suffer from the
same difficulty. I once modified a small color TV to be a monitor.
Unfortunately, it had the same kind of power supply and required an
isolation transformer to be used safely because the chassis was now
directly exposed.

In measuring equipment, typically oscilloscopes, the chassis is
connected to the AC ground pin. Thus the probe ground is equivalent
to the safety ground at the wall. This prohibits using the scope in a
"floating" mode where the ground/chassis would be at an elevated
potential.

Some people simply cut the ground pin on the scope power cord in an
effort to permit this kind of measurement. That results in the
metallic chassis of the scope being at elevated potentials. There's
also the problem when the device being measured has a fault that can
elevate its chassis above ground. There are some scopes where the
chassis is isolated and the scope is battery powered. These are
specifically made for such kinds of measurements (Tektronix 200
series).

The isolation transformer would help run the device in this situation
and prevent possible difficulties. In fact, there is a piece of test
equipment that combines an isolation transformer with a variac, and
has metering to detect leakage to ground in the device plugged in.
This is not a common piece of equipment, though.

As a note, the back of the TV set used to have the power cable
attached directly. Remove the back of the TV and the power cable was
disconnected. A cheater cord was this power cable that did not have a
back attached.

Harvey

>
>Autotransformers and variacs are not generally referred to as widowmakers
>any more than all tree limbs are referred to as widowmakers. The proposed
>use here is safe and in compliance with the relevant standards.
>
>You are dealing with lethal voltages at the output, no matter if it is
>ground referenced or not.
>
>
>
>ST
>
>On Thu, Feb 25, 2016 at 6:30 AM, rolohar@... [Homebrew_PCBs] <
>Homebrew_PCBs@yahoogroups.com> wrote:
>
>>
>>
>> YOU ALWAYS NEED "SAFETY" WHEN WORKING WITH POWER LINE ELECTRICITY!
>>
>> TV "cheater cords" once used in repairing TV sets were known as "Suicide
>> Cords" because the defeated the
>> isolation between the TV set and the power outlet.
>>
>> Autotransformers and Variacs are often referred to as "Widow Makers"
>> because they also do not isolate the
>> user from being exposed to the full potential of the voltage
>> source.......be it 120 or 220 or whatever.
>>
>> Mark My Words!
>>
>> Get a step-up or step-down transformer that has the primary winding
>> completely isolated from the
>> secondary winding and works on the concept of INDUCTION rather that direct
>> hard wired connection
>> to whatever power source you are using.
>>
>> Regards,
>>
>> RFH
>>
>>

Re: drill pcb

2016-02-25 by duwaynes@...

While I was in the military, I had several assignments to countries that used 220 volts.
First thing after getting there was to purchase several 220-110 volt converters for my 110 volt devices.
These were always simple auto-transformers. They were either a metal or plastic box ( depending on power rating) with a grounded Euro 220 v plug on a cord. On the box was a polarized grounded 3 prong 110 volt socket. If everything is plugged in the way it should be there are no problems with auto transformers.
DuWayne
KV4QB

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by rolohar@...

Symons:

Thanks for the dissertation.

It is obvious that you have done your homework.

Regards,

Roland F. Harriston, P.D.

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by rolohar@...

Craig........................Silly!

Roland F. Harriston, P.D.

Re: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by Brad Thompson

On 2/25/2016 10:39 AM, rolohar@... [Homebrew_PCBs] wrote:

<snip>

Variacs and autotransformers only have one winding. There is no
primary/secondary winding
configuration. There is no iron core to facilitate induction between
the primary and the secondary
windings.
<snip>
Hello--

There's most definitely an iron core in an AC-line autotransformer!
There has to be because otherwise there would be
no transformer action to step up or step down the incoming line voltage.

As for troubleshooting older "hot chassis" equipment, for safety's sake
always power the equipment with an AC-line
isolation transformer. If you need to power a 120VAC item from a 240 VAC
line (or vice versa), you can use
a transformer **with isolated windings** designed exactly for this
purpose. These are sometimes referred to as
"industrial control transformers".

73--

Brad AA1IP

RE: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by Boman33

I have been ignoring the back and forth arguing but here is an undiscussed warning:

That a VARIABLE auto-transformer (Variac) works stepping down 220V to 110V does not mean that it can be wired backwards and step up 110V to 220V.

If it is turned down, the output voltage will get higher and higher and it will eventually short the 110V input line. Lots of fireworks and destroyed equipment.

This does not apply to fixed ratio auto-transformers.

Bertho

RE: [Homebrew_PCBs] Re: drill pcb

2016-02-25 by keith printy

I remember the all American 5. My grandmother had one in a metal case. The plug was not polarized and if you plugged it in the wrong way and touched the radio you got “bit”

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Thursday, February 25, 2016 10:39 AM
To: Homebrew PCBs
Subject: Re: [Homebrew_PCBs] Re: drill pcb

A "cheater cord" was (is) dangerous because it allowed a person access to the TV chassis when the back of the

TV set was removed. The original power cord on the TV set was configured so that if the back of the TV was

removed, the power cord came off with the back of the TV set. The "back" of TV sets in those days was

usually made of some non-conductive material like fiberboard or other paper-based material, to

ISOLATE the user from the voltage potential of the chassis.

The power cord was permanantly anchored to this back, so that it was not possible (normally) to remove the back

without disconnecting the power cord.

TV repair men made "cheater" cords that would allow them to power up the TV set with the back removed.

They lovingly named these cheater cords "suicide cords" because they allowed the repairman to be

exposed to the live, powered-on TV chassis, and if he was not careful, he could do damage to himself.

Variacs and autotransformers only have one winding. There is no primary/secondary winding

configuration. There is no iron core to facilitate induction between the primary and the secondary

windings. Autotransformers and Variacs and Rheostats were lovingly referred to as "Widow Makers"

for the same reason..............the user is not isolated from the power source as in a "regular"

transformer. An Isolation transformer generally perfor! ms NO step up or step down function.