On 11/02/11 13:49, Carl Denk wrote: > First I would suggest a hole saw, they are inexpensive, don't require a > huge drill to drive it, make a fairly neat hole, and are available in > 1/16" (1.6 mm) increments. Well, I picked up two hole-saw kits -- a =A310 one from Maplin, and a =A315= =20 one from B&Q. The B&Q one is exactly the same as the "monkey-metal" one I rubbished=20 earlier: a setscrew holding a drill bit in the middle of a metal holder.=20 It sort-of works, but if the saw blade locks up while the drill bit=20 continues spinning, it might (probably will) damage the drill bit. The Maplin one is a little nicer. The saw blades are solid units -- you=20 pick a blade, attach it to the drill bit via a mounting block, which=20 uses an Allen bolt to hold the drill bit in place. The coupler (which=20 goes into the drill chuck) has a few flat edges, apparently to make it=20 easier for a 3-jaw chuck to grip. Similar idea, but the drill bit is=20 more likely to stick in this case -- but even so, once the drill bit is=20 through, it's not a big deal. Unfortunately my POS cordless drill decided to play silly devils. The=20 battery won't hold a charge, and because it's a noname POS, you can't=20 get replacements. That'll teach me to buy no-name kit... Solution: another new toy. A Bosch PSR 18 LI-2. Feels like it was built=20 to hammer nails, fast charge battery, and apparently you can buy=20 everything from case components to the motor, gearbox, switches and the=20 even the speed controller module as a spare part... Wish I'd bought it from Amazon (about =A360 cheaper than B&Q) but I wanted= =20 it today, and paid the price... It's still worth =A3160, IMO. > No matter which method, drill briefly and allow material and cutter to > cool, and if possible a coolant. If the material melts, a rougher hole > happens, and possible to seize tool in hole. That's pretty much par for the course when cutting/drilling any type of=20 plastic. "Go slowly!" I still ended up using a set of files to clean up the hole (and the=20 Dremel to cut off a few bits for the lens mount), but it went pretty=20 well. Just need to give the plastic a good clean and apply a bit of=20 black Milliput putty to get rid of a few light leaks. > 3rd, with dremel, use a 1/8" dia. cutter used to cut wood and drywall > like Dremel #560, 561, or Rotozip cutters. I went looking for the Dremel round-cutter while I was at B&Q -- but not=20 a Dremel tool to be seen. Spent a good 15-20 minutes perusing the=20 "electric tools" aisle, to no avail. > Here again material needs to > be kept cool. A template that the chuck or smooth part of bit rides on > will be helpful, these bits like to wander. In my experience all drill bits like to wander unless you're using a=20 drill press... Plasterboard bits can usually be persuaded into running straight using a=20 bit of masking tape arranged in an "X" over the desired location, and a=20 small hole (made with a bradawl) in the middle. An automatic centre=20 punch works great on aluminium and other soft metals. It's been a while=20 since I've tried the masking-tape trick on plastic, though IIRC it=20 didn't work too well. > If drilling multiple holes in a circle, start with smaller pilot holes, > then using progressively larger bits, say start with 1/8" and stop at > 1/4". In plastic, if the drill gets near an adjacent hole, it might try > to walk into the next hole, then it gets messy. And yet... I didn't think of that. A bunch of 3mm holes joined up with a=20 carbide router bit would have worked pretty well... (... and it's at this point I start re-reading the "panel building"=20 section of Steve Kasten's book, and all the old EPE "Techniques:=20 Actually Doing It!" columns by R. A. Penfold...) --=20 Phil. piclist@philpem.me.uk http://www.philpem.me.uk/ --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .