The special plastic bits have a different point angle (typically 90 degrees vs. 118 degrees for a standard bit) making them work better with the relatively brittle Plex.. Go slowly with it. If you can get it, I also recommend using "Lucite L", which is a type of plastic which is similar to Plexiglas but machines much more smoothly without the melting seen in standard Plexiglas. I've turned Lucite L on a lathe and it cuts like butter, with nice clean shavings instead of sticky melted blobs. Drills nicely too. Good luck. -Tom Computer Collector Newsletter wrote: -- Thomas Hudson http://portdistrict5.org -- 5th District Aldermanic Website http://portev.org -- Electric Vehicles, Solar Power & More http://portgardenclub.org -- Port Washington Garden Club http://portlightstation.org -- Light Station Restoration http://klanky.com -- Animation Projects

Hi, I've worked with the stuff a fair bit...competition car windows, radio gear etc. - even a guitar! Use a sharp, perferably new, bit and drill slowly so as not to melt the plastic. For larger holes, drill a small pilot hole first and work your way up through the drill sizes until you get to the size you want. Don't work on it in the cold, it shatters *much* more easily when cold. Lightly coutersink each side of the hole to reduce stress build-up. Make sure the work is solidly supported on a smooth flat surface with no bits trapped underneath. Practice on a few off-cuts first. All these things found out the hard way :-) Edges can be polished with very fine wet-and-dry paper followed by metal polish or jeweller's rouge. -- Cheers, Stan Barr stanb(a)dial.pipex.com The future was never like this!

Computer Collector Newsletter wrote: I've never seen Plexiglas shatter or split, but small cracks in the corner of a cut or radiating from a drilled hole is very very common. Plexiglas is a nightmare to machine. That includes drilling, cutting to size, sanding, everything. It's very subject to stress fractures, which means you have to cool your cut and cut very slowly and evenly. Unless you're very good with a hand drill or have a drill press, I would recommend Lexan instead. If you do use Plexiglas, there are some things you need to do: Have some spare drill bits, saw blades, etc. You'll probably dull some, and cutting with a dulled bit is very likely to cause cracks. Cool the cut with water or a light soap solution. This reduces stress during the cut, and also carries away the fragments as you cut. Polish all cuts and radius all edges. By "polish", I don't mean "make it shiny again", but remove any tool marks and ridges, and sand the corner off the edges. Any sharp corner, inside or outside, is a "stress relief point". Sounds like a good thing, right? but stress is relieved by cracking at that point. If you're bolting this piece together, or to another assembly, use some kind of rubber/plastic grommet at attachment points. Even with a good cut and good finishing, the stress of tightening screws against the Plexiglas is still risky. Even a stiff "nylock" washer is better than nothing. I'd use Lexan if at all possible, or just build a metal or plastic case with viewing windows. If you do that, you can use clips or adhesive to hold the Plexiglas and not worry about drilling at all. Doc