Homebrew PCBs

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