Be careful with light ferruled heads. The tap can cut through the metal. Experiment by cutting a little, backing out, then checking to make sure that the metal is cut sufficiently without going through to the outside of the ferrule. Practice with a throw away head to get the right amount of thread cut before using it on your good points. Just a bit of experience here from going too deep on judo points. Been using this method for many years as have lots of guys from the local area with good results.