On 2/11/2011 11:12 AM, Philip Pemberton wrote: > On 11/02/11 13:49, Carl Denk wrote: > =20 >> 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. >> =20 > Well, I picked up two hole-saw kits -- a =A310 one from Maplin, and a =A3= 15 > one from B&Q. > > The B&Q one is exactly the same as the "monkey-metal" one I rubbished > earlier: a setscrew holding a drill bit in the middle of a metal holder. > It sort-of works, but if the saw blade locks up while the drill bit > continues spinning, it might (probably will) damage the drill bit. > =20 Gripping the drill bit, and relying on the bit to turn the hole saw, is=20 only for very light work at best. > The Maplin one is a little nicer. The saw blades are solid units -- you > pick a blade, attach it to the drill bit via a mounting block, which > uses an Allen bolt to hold the drill bit in place. The coupler (which > goes into the drill chuck) has a few flat edges, apparently to make it > easier for a 3-jaw chuck to grip. Similar idea, but the drill bit is > more likely to stick in this case -- but even so, once the drill bit is > through, it's not a big deal. > =20 Yep that's what the flats are for, the quality drill bits, larger than=20 3/16" that I buy at the local independent tool store, all have the=20 flats. Drill the pilot hole first just with the drill bit, or a bit of=20 the same size. I sometimes use a piece of 1/4" rod (preferable, machined=20 drill rod, but just plain rod, or even a long bolt cut off works OK) in=20 place of the drill. > Unfortunately my POS cordless drill decided to play silly devils. The > battery won't hold a charge, and because it's a noname POS, you can't > get replacements. That'll teach me to buy no-name kit... > =20 I always buy name brand that there are local repair stations for parts.=20 Long term well worth it. A lot better than at most inopportune time,=20 having to go chase tools. > Solution: another new toy. A Bosch PSR 18 LI-2. Feels like it was built > to hammer nails, fast charge battery, and apparently you can buy > everything from case components to the motor, gearbox, switches and the > even the speed controller module as a spare part... > Wish I'd bought it from Amazon (about =A360 cheaper than B&Q) but I wante= d > it today, and paid the price... It's still worth =A3160, IMO. > =20 Could be counterfeit. I have on order a set of Rayban sunglasses, as=20 hard a I try, I am quite sure they are counterfeit, if they arrive at=20 all. The Seattle address is for the main Seattle newspaper, and they=20 have concurred that they don't have an address there. :( > =20 >> 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. >> =20 > That's pretty much par for the course when cutting/drilling any type of > plastic. "Go slowly!" > > I still ended up using a set of files to clean up the hole (and the > Dremel to cut off a few bits for the lens mount), but it went pretty > well. Just need to give the plastic a good clean and apply a bit of > black Milliput putty to get rid of a few light leaks. > > =20 >> 3rd, with dremel, use a 1/8" dia. cutter used to cut wood and drywall >> like Dremel #560, 561, or Rotozip cutters. >> =20 > I went looking for the Dremel round-cutter while I was at B&Q -- but not > a Dremel tool to be seen. Spent a good 15-20 minutes perusing the > "electric tools" aisle, to no avail. > > =20 Check out these Rotozip http://www.rotozip.com/en-us/Pages/CategoryDetail.aspx?pid=3D9_8# > > Here again material needs to > =20 >> be kept cool. A template that the chuck or smooth part of bit rides on >> will be helpful, these bits like to wander. >> =20 > In my experience all drill bits like to wander unless you're using a > drill press... > > Plasterboard bits can usually be persuaded into running straight using a > bit of masking tape arranged in an "X" over the desired location, and a > small hole (made with a bradawl) in the middle. An automatic centre > punch works great on aluminium and other soft metals. It's been a while > since I've tried the masking-tape trick on plastic, though IIRC it > didn't work too well. > > =20 Haven't tried that, will have to. >> 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. >> =20 > And yet... I didn't think of that. A bunch of 3mm holes joined up with a > carbide router bit would have worked pretty well... > =20 If you have a router, that should work if you make a jig to hold the=20 work and guide the router. Sometimes I have spent much more time=20 building a jig/guide that actual cutting, but end up with a neat hole.=20 Just last night was watching a woodworking show on the TV, the whole=20 show was on router jigs. :) > (... and it's at this point I start re-reading the "panel building" > section of Steve Kasten's book, and all the old EPE "Techniques: > Actually Doing It!" columns by R. A. Penfold...) > > =20 --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .