Many of us use use a spring loaded tapping guide for tapping in either the lathe or milling machine. If you don't have one, and you should, they inexpensive to buy -- US$ 10 to 20 will get you a commercial one. Or an hours time will make one and is a good beginners project. I built the one shown in the first photo about 40 or 50 years ago. It has a 3/8 shank and a 3/16 spindle.
Not so common is a companion to start dies square to cut external thread on a shaft. Fortunately an adapter to go on the tap driver is very quick and easy to make. The one shown is for a 1 inch die wrench but can be made for any size. It is just a thick disk faced off on both ehds. This one is 1-1/8 diameter 7/16 thick. A hole is drilled in one end that will be and easy slip fit on the spindle of the tap driver. This one has a 0.189 diaeter hole to fit lhe 0.187 spindle. Don't drill all the way through. Leave about 1/16 of solid on the far end. In this case I drilled 3/8 deep in the 7/16 thick disc. The other end of the disk is turned down to an easy fit in the back side of the die holder. M holder has a .812 hole in it so I turned the diameter to be about 0.795 or 1/64 under size. This only wants to be a shord distance. About 0.08 works well for me.
A drop of oil in the hole will last for years of use. In use the tap driver is held in the tailstock chuck as usual. The die driver is just slid on to it. The die handle locates on the turned down stub and is then fed into the part with the tailstock. After it touches the part feed the tailstock in another 3/16 of an inch or so to apply spring pressure. The die is now centered on the part and square to it so thread away with no drunken threads.
Gail in NM
