I agree on all points.
With a large press and the friction and spring pressure involved in the
pinion feed, and the good lever action, makes for practically zero
feedback about the force on the drill (and that is tiny in the first place
because of the size).
Before i put a vice as counterweight on the back of my pivoting press the
weight of the arm and spindle would feed the drill too fast, especially at
low RPMs, which broke a drill. Now that it is balanced i get a very good
feedback of force from it, i guess the counterweight is a bit better here
than a spring, and the almost frictionless thrust bearings help too.
There's definitely a difference in "drag" between a fresh out of the box
drill and a well used one, although the holes will still be nice and clean
with a slightly dull drill and i see no reason to stop using it.
If you feed slow enough for the RPM, and board and spindle is solid, and
there's not too much runout, the drills won't break, of course. But
carbide drills are about the most brittle drill one will ever work with,
and usually the smallest too, so it takes some attention to get it right.
I have tried different arrangements, including a spindle holder for a
drill stand inctended for normal power drills, and nothing worked really
well. The pivoting press does what i need - hold the drill exactly upright
and in place while allowing me to feed it freely. With it i only break
drills when making mistakes.
Anyway, it's not a problem, but it isn't the same as drilling a 8mm hole
in a piece of wood either.
ST
On Sat, 17 Dec 2005 13:20:24 +0100, lcdpublishing
<
lcdpublishing@...> wrote:
> While I am/was a machinist and have plenty of experience drilling
> holes with a wide variety of tools, I am very new to drilling in PCB
> materal. I have only drilled a thousand or so holes so far.
>
> However, what I have learned is that the same rules apply to
> drilling PCBs as any other thin material - with one exception which
> I will explan last....
>
>
> Speed isn't that critical for PCB material - It drills fine at 800
> RPM and at 3500 RPM and at 20,000 RPM. When drilling on my drill
> press, I use around 1500 RPM or so, it's quiet and works well. The
> more RPM does help, but isnt' critical. Adjust your rate of feed
> accordingly with the RPM.
>
> Stable backer board and hold the PCB down. MDF makes a good backer
> board to rest the PCB on and to drill into - It's cheap. As the
> drill bit breaks through the back side of the board, it will have a
> tendancy to lift the PCB up, hold the PCB down to prevent this.
>
> Exception -----
>
> When drilling the PCBs on a drill press and positioning the work by
> hand, it is very natural for someone to get the spot lined up, then
> quickly pull down on the handle. PCB is soft and drills easy so the
> assumption is to drill quickly. As you get tired, this tendancy to
> feed quickly also increases. This is probably the biggest cause of
> broken drill bits.
>
> When drilling hard woods or more so with metal, there is "feed back"
> in the lever to indicate you are feeding with enough presure, with
> PCBs this isn't very noticable. So, to help guide you a bit, try
> this the next time you sit down at the drill press.
>
> Line up the part with the drill bit, gently pull down on the handle
> until the bit contacts the part. Now, try to time the cut to last 1
> second - no less. You will notice right away this is about 10 times
> longer than you naturally been doing it AND you will also notice
> that the part has much less tendancy to lift off the drill press
> table.
>
> Practice that for a while and you should see a difference right
> away. As for broken bits for me when drilling PCB material....
>
> So far this is what has broken the bits for me...
>
> 1) Dropped on floor
>
> 2) Poked hole in finger while trying to get it out of the little
> box, not once, but twice. The second time it stuck in my finger and
> when I pulled back in pain, it stuck and flew against the wall.
>
> 3) Kept drilling after I was tired (probably 40 holes or so) and
> didn't feed slowly enough and the PCB rode up the drill bit. Then in
> reaction, I pushed the board back down and bit broke
>
> 4) I tried to drill a hole free-hand with a dremel - bit broke
>
> 5) I lifted the part up off the drill press table without first
> sliding it out from under the bit - bit broke
>
> 6) I tried to drill a hole in a PCB at the drill press but with most
> of the components installed on the board. The board would not sit
> flat during drilling and the drill broke.
>
> I believe that pretty much sums up my experience so far with
> drilling PCBs.
>
> Chris
>
>
>
>
>
> --- In Homebrew_PCBs@yahoogroups.com, Mycroft2152 <mycroft2152@y...>
> wrote:
>>
>> As strange aas it may seem, in my supporting Stefan,
>> bits do break and often. Stefan is not a klutz. :)
>>
>> I thinks it's a difference in perspective, if you are
>> a machinist, with the right tools, knowing the correct
>> procedures and used to machining steel; drilling a few
>> holes in epoxy fiberglass is easy.
>>
>> For the rest of use who are weekend warriors, drilling
>> ususally means putting few holes in a 2 x 4, it's
>> difficult to downsize the procedure.
>>
>> what may be a 'hair off' to the weekend builder, will
>> look like the grand canyon to the experienced
>> machinist. Combined with the diffence in tool
>> sharpening (if ever), it all adds up to drill
>> breakage. At the low cost of drills, it's not a big
>> deal to the weekend builder.
>>
>> TANSTAAFL
>>
>> Myc
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