Need Help!- Help milling small holes in polycarbonite

[Ferny]

Hey Guy's looks like there is a lot more traffic in this forum than the plastic forum so I'll post here.

I need to drill or mill 256 (16X16 grid) holes on 0.100" centers in 1/4" thick Lexan. My smallest collet on the router is 1/8" so the bit is reduced to 1/16".

I tried using a 20IPM feed and ~8000 RPM's and the first 8-10 holes were real nice. Then the swarf started building up on the bit and it broke when I wasn't looking. What can I do to make this work? Do you only drill 10 and stop to clean? Do you drill 10 then go to a scrap portion and drill a deeper hole to push the swarf up the bit? Do you keep plugging away breaking bits until you find the right speed and feed? That bit is so tiny I'm afraid I'll break it If I feed any faster???

Please Help.

Thanks,

Ferny.

[One of Many]

I'd just drill them with a low rake drill and air blast nozzle to cool and rid the bit of chips. You could peck cycle to keep the chips clear and the bit cooler too.

If you have a bench grinder with a right hand side sharp corner on the wheel. Or dress it to suit. You can grind off the hook at the cutting edge into into the flute face, toward the centerline of the bit so that both faces meet in the center. (resembling a 2 lip phillips screw driver point?) Reducing the flute rake will keep the back side of the hole crisp without breaking out. You must feed it fast at 8000rpm and keep the chip/bit moving without feed dwell. A little cooking spray can keep the material from sticking to the cutter. PC can be chemically sensitive to some solvent cleaners, crazing on contact or shortly thereafter.

DC

[Ferny]

Thanks, We tried about 20-30PSI aimed right at the bit and upped the feed rate to 40IPM and slowed the router to minimum. The next closest drill we had was 0.050" so we gave it a shot. The swarf blew off almost every time on the next hole start and was a good 2" long and straight with a twist. Looked like cotton candy building up in the corner of the enclosure!

It's hard to believe you can feed that fast with such a small bit! We have a lot to learn and all it takes is some tooling $$ and a bunch of questions from you guy's that do this for a living!

Thanks a lot!

Ferny.

[One of Many]

Glad to hear it all worked out.

Nice fishies!