Broken Tap Removal
by David F. Bryant
Over the years I have drilled and tapped hundreds of holes for scope mounts on various rifles and pistols. On occasion I will break off a tap, especially in old military rifles.
When this happens, I leave the mill in position and mount a carbide grinding bit or carbide drill that is smaller than the drilled hole and then crank the spindle speed up to max on the variable drive head of my Bridgeport. Feed the bit into the broken tap using a little sulphur based cutting oil and watch the center of the tap turn to dust and smoke! The remaining threads in the hole will be undamaged.
You may have to hit the top of the broken tap to “level” it off before drilling; I use a small hammer that I have rehardened the face on to do this. This technique works well with larger taps as well; just use a carbide drill a little larger than the center web of the tap and the tap threads can be removed easily.
Starting a Tap in the Drill Press
by Douglas Graham
When tapping in the drill press, I lower the tap to the hole with the spindle off and then pull the handle down to start the tap under some slight pressure. A little tapping fluid is very helpful. I clamp the tap in the drill chuck firmly, but not too tight, and the tap will turn in the chuck jaws when it is just a little way in. Then, I shut off the drill press and continue by hand with a tap wrench.
This procedure gets the tap started straight in the hole and, provided you don’t over-tighten the drill chuck, it’s easy on the taps. I’ve been doing it this way for 40 plus years!
