Just a question of interest, but how do you drill a hole using a .012" drill bit? This question came up when a couple of us 2nd year precision machinist apprentice found a .012"drill bit in a cabnet on the shop floor (we do not drill anything that small). Also how do you check something that small for TIR? This information would be a great topic for my Metal Cutting class. Thanks for any and all responses.

At my age I can't see a hole that small, so I wouldn't bother to try. :)

First, you look all over creation for a drill chuck that will hold it:D ER16 collets won't go that small, and many drill chucks which are rated 0 to 1/4" are really .030 to 1/4". Maybe the smaller series of ER collets will hold tiny drills, I've never bought anything smaller than ER16.

Buy a 10 pack of drills.

Buy a sensitive drilling attachment, which is a spring loaded drive, on which the drill chuck mounts. The drill press then provides the rotary motion, and you apply fingertip pressure to the thrust flange of the sensitive drilling attachment, and can very tenderly drill the hole.

Break through is the most critical moment when using a sensitive drilling attachment. Make sure to back up the part with something to stabilize and slow the exit of the drill point.

CNC is actually quite good for small drills, as the feedrate is very nicely controlled. However, you need to have a good bit of background experience to know what the drill can take for a feedrate, and how deep it can go per peck. Hence the requirement for a 10 pack of drills :D

What is really amazing is the guys who can make the flutes in those tiny drill bodies.

Hu is correct. An alternative is to EDM the hole with a hollow copper tube with a .010" OD. It will produce a .013" ID hole (in my experience). It can be measured with a toolmakers measuring microscope with the proper (reticle?) installed. Flushing can be accomplished by feeding fluid thru the hollow tube. This setup can drill quite deep if you keep the tube straight.

My printed circuit boards regularly have < 0.012" holes (for vias).

It is common in the pcb industry to use > 30,000 rpm spindles and a backing material; the carbide drills typically have a 1/8" shank.

One man's technology is another man's magic ;-)