Metallics 789CTB Carbon Steel Tap Bottoming Type 7/8-9 (1pc)

The 789CTB cuts a 7/8-9 thread, meaning 7/8 inch diameter at 9 threads per inch. That is the standard UNC coarse thread for 7/8 inch rod and bolt stock, so it will chase or clean up threads on 7/8-9 all-thread hanger rod and 7/8 inch coarse bolts.

The 789CTB is a bottoming type tap, which means it has almost no chamfer on the lead threads so it can cut threads nearly to the bottom of a blind hole. Use it when you need full-depth thread in a closed hole, such as a drilled and tapped boss or a blind hole in a beam clamp or bracket. For starting a thread from scratch in a through hole, a taper (plug) tap is easier to align and start; many jobs use the taper tap first and then finish the blind hole with the bottoming tap.

It is a carbon steel tap. Carbon steel holds an edge well for hand tapping and thread chasing in mild steel and softer materials, and it is the usual choice for field work where a tap gets used occasionally. For production tapping or harder alloys, a high speed steel tap stands up to heat better.

Yes, that is a common use. A 7/8-9 tap will chase rust, paint, or burrs out of an existing 7/8 inch coarse internal thread so a rod or bolt runs freely again. Because it is a bottoming type with a very short lead chamfer, start it square to the hole, since there is less taper to help it self-align than on a taper tap.

One tap per pack, supplied in a pouch. If you are stocking a truck or a maintenance shop and want a spare on hand for a 7/8-9 thread, order the quantity you need rather than expecting a multi-piece set.

Order it as Metallics 789CTB. The number reads as 7/8-9 thread, Carbon steel, Tap Bottoming, which is useful when you are specifying several sizes from the same family on one purchase order.