Metallics 7814CTT Carbon Steel Tap Taper Type 7/8-14 (1pc)

The 7814CTT is a 7/8-14 tap, so it cuts a 7/8 inch diameter thread at 14 threads per inch. That is a UNF (fine) pitch rather than the coarse 7/8-9, so it only matches fasteners and fittings already threaded 7/8-14.

A taper type tap, which is what the 7814CTT is, has a long chamfer across several leading threads so it starts square and easy in the hole and cuts gradually. It is the one to reach for on through holes and for starting a thread by hand. It will not thread to the bottom of a blind hole, since the tapered lead leaves the last threads incomplete; a plug tap follows it partway and a bottoming tap finishes the hole.

Carbon steel. That suits hand tapping and chasing or cleaning up damaged threads in mild steel at low speed. For production machine tapping or harder alloys, a high speed steel tap is the better choice, since carbon steel loses its edge with heat.

One tap per pack, supplied in a pouch. If you need taper, plug and bottoming for the same 7/8-14 thread, each has to be ordered separately.

Yes, that is a common use for a carbon steel taper tap. The tapered lead lets it pick up existing threads and run straight, and 7/8-14 matches the fine thread on the part you are repairing. Back it out often to clear chips and use cutting oil.

A 7/8-14 thread uses a 13/16 inch tap drill for roughly 75 percent thread engagement. Drill that first, then start the 7814CTT taper tap square to the work.

It is a hand tap by design. The 7814CTT is carbon steel, which is meant for a T-handle or tap wrench at low speed with cutting fluid. Powered tapping generates heat that dulls or snaps carbon steel taps, so for machine work specify a high speed steel tap instead.