Homebrew PCBs

On Sun, 02 Oct 2005 16:14:15 +0200, Andrew Mawson <andrew@...>  
wrote:

> I tend to use resharpend drills (as they are cheaper and so am I !)
> but
> use a collar to set the length to a standard so changing mid way
> through a board is less hassel.
> The 1/8" drill shank has a 3mm collar forced over it so is a very
> tight
> fit.
> Actually adjusting the collar to sit so that the drill tip (or more
> critically a fishtail cutter tip)is exactly where it should be is a
> bit
> hit or miss and I wondered if anyone else uses this method and if so
> has a magic way to adjust them.
> I sat down to design a screw device to force the drill through the
> collar until it touches a contact and lights an led, but then
> realised
> that the collars vary in thickness and the critical reference is from
> the TOP of the collar to drill tip.
> AWEM


I have a screw device too, i didn't sit down to design much though....

It's just a large nut with a short piece of copper tubing soldered to it,  
and a washer soldered on the end of that.
There are also two large screws, one with a small indentation and one with  
a small stud. the first one is used to move the ring around and the second  
one can push the drill out all the way if i need the ring for another one.

All the rings i have are same thickness, and i manually set them (maybe  
0.2mm tolerance). If the rings are not the same one could build a similar  
screw adjuster that uses the top side as reference.

ST