Originally Posted by 2door
Micro drills like to spin at 15K??????
Strange. I use mine in a pin vice and rotate it with my fingers. Are you sure we're talking about the same thing?
Pin vices are good for cleaning burrs in holes with the right drill, but not for actually drilling. If you do you risk cutting a hole that's not straight, round, or to size. Also those drills are very easy to break. If you want a nice surface finish in the hole the best way is to use a drill press with a dremel attached and turn it up to the highest RPM and drill with multiple light pecks and some cutting oil or wd40. Actually micro tools like to run at up to 30k-ish. Parts like jets are made on Swiss screw machines which are similar to CNC lathes only they are somewhat smaller and have multiple axes, chucks, high pressure oil coolant systems that allow for drilling very long holes in very small parts accurately and quickly, usually live tooling on different sides - so the drill spins at let's stay 10k and the chuck spins at another 10k for a combined 20, etc. And their precision is much higher than lathes. So if you were to drill a jet bigger you'd need to go into the side holes with a pin vise and either a drill or sharp edged precision gauge pin to deburr, then go down the main jet and deburr, repeat until no burrs. A screw machine can cut over 30 jets a minute... I would just buy these jets as is and not mess around with drilling them..
Also you won't be able to measure a small drill accurately enough with a caliper. The difference between jets is only .0004", my own measuring tolerance is around .0005" or so and that's on rectangular parts. Round parts? Forget it. Only thing that will work is a 1" micrometer that reads thousandths, tenths mics are the same only they also have a vernier scale on the side for the tenths.
If your drill chuck isn't small enough to hold a tiny drill you can use a pin vise to hold it, but there are some steps. First off you must check the runout. With a small drill just hold a piece of white paper behind it and see if it runs out. If it does at all you'll have to stick it out very far and drill with it deflecting somewhat so that it "follows the hole". People do this frequently with reamers. Other thing is that a pin vise won't hold it too strongly like a micro chuck so you need to go slow.