Tapping with the Tension/Compression heads can be a struggle.
Sometimes the spring compresses on entry and you won't achieve accurate depths.
For thru-holes, I always go an extra 2-3 threads deep to compensate.
Also, G84 doesn't work so great on Tormach's without an encoder.
It's better to do long-hand programming for tapping instead of using G84.
Feed in... PAUSE (one second for the spring to relax)... Reverse Spindle... Feed out
On Tormach's website (and in the manual), there's instructions for long-hand programming for tapping.
For these reasons I prefer Threadmilling.