Typical specials include self-captive tapping screws and double-thread combinations. Self-captive screws combine coarse-pitch starting threads with a finer pitch farther along the screw shank.

Historically, the threading of holes has been a fairly straightforward operation, usually performed close to the end of a part’s machining. Once the holes had been drilled, thread taps of the ...

Twist drills do not make accurately sized or good finish holes; a reamer of some type is often used to cut the final size and finish. A reamer will not make the original hole; it will only enlarge a ...