TAPS - High Speed Steel

From experience in the shop, we have learned to not use carbon steel taps and dies.  While carbon steel taps can be broken out of a part if the tap breaks, we have found they break far more easily than do taps made of High Speed Steel.  As a result, we don’t even allow carbon steel taps in the shop.  While High Speed Steel taps and dies are slightly more expensive, the much lower rate of breakage more than makes up for the difference.   We find very little use for taper taps; plug and bottoming being almost exclusively used here.  We use gun taps (spiral cutting taps) whenever possible.  The big advantage here is that the tap drives the chips before it rather than loading up the flutes, which is the major cause of breakage.  Of course, with a blind hole, if threads are required all the way to the bottom, a bottoming tap must be used to finish the threads.  A suitable cutting oil for the material being threaded will go a long way towards preserving the sharpness of the tool cutting edge and lowering the effort required to generate threads.