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From: "Barry L. Ornitz" <>
Subject: Re: drilling holes in PCB's
Date: 01 Dec 1998

Paul Gustafson wrote in message <>...
>Hi John,
>Dremel makes a drill press type adapter for their tools. {snip}

Make sure the press is rigidly attached to your workbench, and use as high
a speed as possible for the small drill sizes.

>I made a pulse width modulated variable speed reversible power supply for
>the motor. It turns about 3600 rpm wide open and is just right for pcbs
>and other small stuff.  Good luck with your project,
>Paul G.

This is really far too low a speed for carbide PCB bits.  If you have ever
done work on a lathe, you probably learned about cutting speed in inches
per minute (or meters/second).  As the work gets smaller, you need to speed
the lathe up to maintain the same cutting speed.  The same thing holds for
drilling.  The smaller the drill bit, the faster it needs to turn.  The
cutting speed for a drill is based on the radial distance of the edge to
the bit center.

The printed circuit board manufacturing industry typically uses air turbine
driven drills.  It is not uncommon for these to turn at 100,000 RPM or
more.  And if you thought high-end audio equipment was expensive.....
:-)       You might talk to a friendly dentist, however.

There are prototype PCB shops that will turn out a single (or perhaps up to
50) boards for a nominal cost.  They typically expect the design to be
given to them in Gerber format, although many other formats are also
supported.  I use Orcad to design my boards, and I can call the company I
prefer to work with (Volunteer Circuits, Bells, TN) and upload my files.  A
few days later, I get back solder plated double sided board with excellent
plated through holes.  Multilayer boards take only a little while longer.

If you insist on drilling the holes yourself, the drill press needs an
extremely well centered chuck.  The carbide drills cannot withstand ANY
flexing.  I have never seen a small one (#55 or smaller) survive drilling
with a portable drill yet.

If you have access to steel piano wire in straight lengths, you can make
your own drills.  Take a one inch piece of the wire and file the end down
to a slightly blunt point.  This will typically make about three holes in
fiberglass/epoxy circuit board.  Throw it away after this.  A commercial
high speed steel bit last just a few holes more and costs many times more!

            Barry L. Ornitz

From: "Barry L. Ornitz" <>
Subject: Re: Where to get PC board drill bits?
Date: 26 May 1999

Assortments of such bits are often sold by surplus dealers (*).  Commercial
PWB houses generally do not sharpen the carbide bits, but even when they
do, they stop when the bit gets too short for stacked boards.  Thus many
appear surplus.

The only problem with carbide bits is that you cannot use them in a
hand-held drill.  They really need an accurate drill press.  Any side
torque and they snap as the carbide is extremely brittle.

With glass/epoxy boards, ordinary steel bits only last a few holes.  A
carbide bit will last many orders of magnitude longer.

        73,  Barry L. Ornitz     WA4VZQ

(*)  I think Alltronics has carried them in the past.

Don wrote in message <>...
>I wonder if anyone can give me an Idea of places to order small drills (
>somewhere in the vicinity of size #70) for drilling homemade pc boards?
>I have quite a few electronics and surplus catalogs, but most of them
>dont carry bits this small. They dont neccesarily have to be carbide.

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