I once in my machinist career had to tap blind holes for some small screws in H900 17-4PH stainless. I broke the first several I tried by hand tapping. I was building the part on a CNC machine. One could set the spindle to stop at a given depth & reverse rotation. I calculated the feed rate to accommodate the spindle speed in relation to threads per inch. I then proceeded to "Power" tap the rest without breaking another tap. I have tapped hundreds of holes by simply chucking the tap in a drill chuck on a Bridgeport mill & hand feeding by feel. This works great on a through hole, but not so well for a blind hole.
We used a lot of two flute taps which had the lead ground to curl the chip ahead of the tap, which was called a "Gun Tap". This designation had nothing to do with firearms, but because they were designed for power tapping.
You can actually power tap under conditions which are near impossible to tap by hand. You can believe it or not as you see fit but with over 35 years in machine shops, I tapped a "LOT" of holes both by hand & by power.
