I don't use anything less than 0.3mm, anything smaller and the breakage rate increases dramatically. 50% of the time I will use a pin vice then the other 50% I will twist the drill between my fingers, depending on the job at hand. On average when using a 0.3mm drill bit I can drill 30 - 40 holes in plastic without breaking a bit, this includes blind holes where the drill bit has to be withdrawn before cutting through. I also use these bits for drilling into thin brass sheet and micro brass tubes and have had a lot of success, occassionally a bit will break when it is just about to break through the other side of the tube or sheet but I can usually "feel" when this is about to happen and I back off a little then run a HSS bit through to finish the hole off.
I have never used my Dremel with these drill bits, I think that it would be too difficult to hold the machine steady while drilling, you have to bear in mind that these small drill bits are designed to be operated in machines which rotate at 100,000rpm, the high speed gives the drill bit its strength, my Dremel nor my pin vice comes anywhere close to that speed.
For the accuracy and sharpness of these carbide drill bits they outweigh the usual HSS drill bits, especially in the smaller sizes, they are extremely sharp and will cut through brass tube with ease leaving a very clean hole, plastic drilling is a breeze. Don't forger, when removing the drill bit after drill into plastic reverse the direction so the bit will screw itself out of the hole, this will eliminate a lot of breakages.
To clean out a pre-existing hole I always use a HSS drill bit, no need to risk a good carbide drill bit just to get some paint out of a hole, and because the carbide is so sharp it will quite easily drill deeper without you knowing about it.
Des.
