Chuck Adapter Collets for Very Small-Diameter Bits

A CNC can drill a 1/16th-inch pilot hole, but you may need a custom-made adapter for chucking the bit. November 29, 2014

Question (WOODWEB Member) :
I want to drill a very small starter/locator hole for a screw. What is the smallest hole you drill with your machine? What bit setup do you use? I will be using a drill bank.

Forum Responses
(CNC Forum)
From Contributor D:
For slide and hinge plate holes I use a through point 5mm and drill .125 deep. For through holes I use a 1/8 bit.



From the original questioner:
How do you chuck the 1/8th inch bit?


From Contributor D:
With an adapter to fit in my 10mm collet.


From the original questioner:
I can find down to 2mm adapters but none for US sizes.


From Contributor B:
For very small tooling you can use a collet chuck extension like a DA200. This is a tool holder that will fit into your normal collet. Then get the whole series of the collets and your good to go.


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From the original questioner:
Is it flawed thinking to try and drill holes smaller than 2mm. Will I get lots of broken bits?


From Contributor B:
You are getting the broken bits because you are drilling too fast for the material that you are drilling or maybe you need to peck drill or change you spindle speed. The pilot hole diameter should be determined by the screw size that you are using.


From contributor M:
I just use an 1/8" bit, or 3.2mm which is the metric equivalent. I use split drill bushings from Amana Tool and they seem to work well. They are pretty simple adapters and work in either LH or RH rotation drill spindles so it doesn't matter which one you decide to use as your spot for the small tool.


From Contributor U:
Someone must make smaller adapters. I have one that has a 1/16" drill in it and it came with one of the used machines I bought and no markings on it so I do not know who made it. Something a machine shop could make or modify for you though.


From Contributor I:
You can buy a 3mm and 3.2mm from Amana with a 10mm shank, no adapters needed. I through-bore screw locations on all panels and Iíve only have had one break in five years.


From contributor M:
My local tool supplier has made them as small as 1/16" diameter. They are very easy to make.