Dave, in the aircraft industry where those are mostly used, they are called micrometer countersinks, and indeed you can make high precision countersinks with them, accurate and repeatable to .001" in depth. The aircraft mechanics mostly use them for countersinking Alclad aluminum sheet for exposed flush countersunk rivet heads. I have just one of them, and it is a treasured tool. The aircraft guys also use angle air drills with a very short 1/4-20 socket and short threaded drills, countersinks, counterbores, etc. (like those at the left side of your photo) for working in the tight quarters of aircraft wings and other god awful places with poor access. I am looking for one of those air drills for a reasonable price and with a reasonably slow speed. I have lots of the 1/4" tools, and they are sold cheap on ePay, high quality, too.