Metallics 5818CTB Carbon Steel Tap Bottoming Type 5/8-18 (1pc)

It cuts 5/8-18 threads, which is the UNF fine pitch for 5/8 inch. The coarse equivalent would be 5/8-11 UNC, so if the bolt or rod you are threading for is coarse, this is the wrong tap. Check the mating fastener's pitch before cutting.

Bottoming taps have almost no lead chamfer, so they cut full-depth threads right down to the base of a blind hole. That makes the 5818CTB the finishing tap you reach for after a taper or plug tap has started the hole, or when you need usable threads to the very bottom of a drilled pocket. For starting a thread from scratch in a through hole, a taper tap enters straighter and is easier to keep square.

The 5818CTB is a carbon steel tap, which suits hand tapping and occasional cleanup work in mild steel, aluminum, and brass on electrical installs. Carbon steel loses hardness with heat, so it is not the tool for powered tapping, production runs, or hard alloys and stainless. For those, use a high speed steel tap.

Yes, that is a common use. Because the bottoming design carries full-depth threads along nearly the whole length, it will clean and re-form a damaged or paint-filled 5/8-18 hole, including one where the threads have to run to the bottom. Go slow by hand and back the tap off to clear chips, since carbon steel will not take the heat of power driving.

For a blind hole, yes in most cases. A bottoming tap has little chamfer to self-align, so starting with a taper or plug tap in 5/8-18 and finishing with the 5818CTB gives straighter threads. In a through hole where thread depth at the base is not a concern, a taper tap alone will usually do the job.

One tap per order, supplied in a pouch. If you are stocking a service van or multiple crews, order a count per truck rather than expecting a multi-pack.