Re: PCB drill working

[mjmahon@aol.com (Michael J. Mahon)]

Rich J.replied:

>"Mark Cummings" <NOTfigjams@primus.com.au> wrote in message
>news:<3b1b8703@news.iprimus.com.au>...
>> For that to work you will have to sit the PCB up off the cutting table a
>bit
>> using some kind of spacer, to allow for the tapered end of the drill bit,
>> otherwise your holes will not be complete.
>
>Yes, that is a good point.  A spacer the thickness of the distance
>from the tip of the bit to where the taper ends.  I may add some sort
>of microswitch or encoder to get drill depth feedback from the plotter.

Or, even simpler, without a spacer, note the time from "drill start" to
"first contact", then add a small fudge factor (like 10%) to clear the
hole.  Now that I think about it, if the variation in drilling time is due
to board thickness rather than board hardness, then the fudge amount
should be a fixed add-on, rather than a percentage, since it's determined
by the bit geometry, not the board thickness.

-michael

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