Our extension taps are made to conventional tap dimensions.
Extension taps have an extended shank to reach inaccessible, long reach holes. Thread length, shank diameter, and shank square are made to standard specifications listed in Table 302 for machine screw and fractional taps, and to Table 311 for pipe taps. Extension taps are available in both hand and spiral point styles, and in small shank style. Tap body elements are made to Table 303-A Special Extension Taps specifications.
Two distinct types of extension taps would be Pulley taps and Nut taps as described below.
Pulley Tap – The hub portion of pulley parts contain oil cups and set screw holes, most of which cannot be reached with ordinary hand taps. Pulley taps have the same basic thread dimensions as hand taps, but pulley taps differ in that they have a longer shank which is of the same basic major diameter as the threaded portion. When tapping pulley hub holes, the taps are inserted through holes in the rims which are slightly larger than the shanks of the taps. These holes serve as guides or bushings for the taps to assure proper alignment when tapping. Pulley taps can also be used for general tapping in parts where an extra long length is required to reach the holes being tapped.
Nut Tap – Nut taps feature a long chamfer which assists in entering the drilled hole, and distributes the cutting action over several teeth. These taps were initially designed for tapping nuts and have a long thread length. The shank diameter is smaller than the tap’s minor diameter to allow the accumulation of several nuts after tapping. Nut taps also feature an extended square length.