A pressure foot on your drilling spindle will help with burrs or warped panels. It could be nothing more than a spring loaded ring or U shaped foot that compresses the stack of boards right before the drill bit enters. I always used .125" tempered masonite as the back up board. The entry material was .010" aluminum or phenolic sheet.
Most drilling machines use a pin and slot tooling plate. The stack of boards are pinned together with .125" dowel pins. We ran 12" x 18" and 18" x 24" panels that were pinned half way across the shorter dimension on each end. The dowel pin holes were drilled about .25" from the panel edge. One pin went into the bushing hole and the other end of the panel went into the .125" wide tooling slot. This pin and slot tooling allowed panels of any length to be pinned to the tooling plates.
You could make a pin and slot tooling plate for your bridgeport that clamped to the t slots. MDF or aluminum would work good for this. Just clamp the plate to the table and write a program that drills a tooling hole and cuts a long slot.
I've never seen a circuit board drilling process that left no burrs. That's why every plant has a conveyorized deburring scrubbler. For small jobs you can wet sand the panels with 220 grit sandpaper. That works fine for deburring.
--- In Homebrew_PCBs@yahoogroups.com, "designer_craig" <cs6061@...> wrote:
>
> Thanks for the info.
>
> I took a guess at a starting point and used 5400 RPM & 8.6 IPM on a .042" dia carbide bit. Seemed to work just fine, had some burs on the back side but they sanded off without much effort. I was using some masonite as a backer but possibly I need something a little more dense to help reduce the burs.
>
> Eventually I am going to build an accessory high speed spindle attachment to get the RPM up to 25K to 30K.
>
> I also need to build some sort of holding fixture possibly a vacuum fixture to hold the blank boards.
>
> Craig
>
> --- In Homebrew_PCBs@yahoogroups.com, "designer_craig" <cs6061@> wrote:
> >
> >
> > I just finished up my CNC quill drive conversion my Bridgeport and would
> > like to use it to drill boards. I have not found a reference to what
> > speeds and feeds to use for drilling.
> >
> > I am looking for the surface feet per minute and feed per turn numbers
> > for small carbide drills in FR-4. My 5400 RPM maximum going to be
> > well below the 30,000 to 60,000 RPM used by a real PCB drilling spindle
> > but it should still work fine if I use the correct feed rate.
> >
> > Anyone got a reference for these parameters.
> >
> >
> >
> > BP Quill Drive
> > <http://picasaweb.google.com/lh/photo/B-uAtxYUicys82cFdd5HYg?feat=direct\
> > link>
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>