Tapping holes while material is still clamped to my mill table?

[Robin Hewitt]

(by the way...in the tool management of my CNC software, I see there are 'tap' tools available as an option to select...what's going on there?!!! My spindle turns at 7000RPM...how on earth can you tap a hole that way!! :confused: )

You can fly cut a screwthread with cnc, spiralling dwn in to the hole but the tool needs to have a considerably smaller radius than the hole.

Have you tried a spiral flute taper tap? That woiuld destress you somewhat at the fracture point