I read it about 40 years ago in the CC library in Colorado Springs! I am not even?sure of the date! Try google say" DIY EDM Cheap"? Bill
In my home hobby projects, I've usually only tapped holes in the range from 6-32? up to 1/4-20. The smaller 6-32 and 8-32 taps still make me nervous, even when tapping aluminum. Even when using a guide or tap follower to keep things straight, and using tapping lube, my biggest question has always been "how much torque should I be applying, and how much is too much?" Like many hobbyists, I started out with one of those large sets of "tungsten steel" taps and dies. The taps are typically plug taps, so I find the cut is quite aggressive. I will start off with a hole drilled with the recommended number drill, but more often than not, the tap will not start properly, even if I chamfer the opening of the hole. So, I go up to the next-larger number drill, and try that. Often I have to go up two drill sizes to get the tap to start. I know I'm giving up some thread engagement by doing this, but the results have been acceptable for my projects.
But, this past week, I bought a set of HSS taper taps, from 6-32 to 3/8, from an industrial supplier. I'm hoping that the less-aggressive taper taps will give me more luck in starting the tapping, and less anxiety? when trying to decide how hard to twist the tap wrench.
