Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

A previous post compared a Foredom handpiece and a Dremel for runout - a serious consideration when using solid carbide bits. They were 0.006" and 0.003" respectively.

So I thought I should go measure what I had available. I had always been told to use collets for accuracy and to minimize runout. Jacob chucks were always a no-no when it comes to precision work. My Dremel and new Foredom #40 both checked out at 0.003". So while I was at it I checked my 25 year old heavily used Unimat SL, which only has a Jacobs chuck. It came in at 0.001" of runout and the drill shaft was dead parallel to the axis of rotation.

So much for conventional wisedom. A collet won't get much better than that so I guess I know what I'm going to use for my PCB drill. I always tell my customers that if you don't measure it you don't know what it is. I should listen to myself.

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