I have a heap of small holes to tap shortly and I want them to be firstly straight, and secondly I dont want too many (nil!) broken taps. I therefore needed a piloted tap driver!
Almost all my holes are 4 BA so Ive built this around that particular size. I will make a few more in common sizes though...
The unit itself is quite simple BUT... I had my first attempt at knurling, and while not perfect, Im pretty impressed with the result...


I might just go and knurl something else.....

P.s. that a 4 BA die next to it for reference... centre shaft is 12mm.