Re: PCB drill working

["Mark Cummings" <NOTfigjams@primus.com.au>]

I assume Rich was going to place the PCB onto a metal plate, so drilling
past the point of contact would mean drilling into the metal, reducing the
lifespan of the drill and making a mess of the table.

Mark


Michael J. Mahon <mjmahon@aol.com> wrote in message
20010604163724.24820.00000011@ng-fy1.aol.com">news:20010604163724.24820.00000011@ng-fy1.aol.com...
> 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
>
>  Email:  mjmahon@aol.com
>  Home page:  http://members.aol.com/MJMahon/