The term extension tap includes distinct application tools but refers to any longer than standard USCTI table taps. They include pulley taps, nut taps, bent shank taps for volume nut tapping machines and simply standard thread taps with either a shank larger than the major diameter of the thread or small shank having a shank size smaller than the minor diameter of the thread. Pulley, nut and bent shank taps are for a very specific purpose. The shank of a pulley tap is a guide tapping pulleys and other hard to reach parts. Nut taps are common in conventional machines when tapping special nuts, running onto a long shank. Bent shank taps are either brazed or screwed into long extension shanks for high volume tapping on special nut tapping machines . Large shank and small shank extension taps are used when reach to the part, or in the case of small shank tools the tap can cut threads longer than the length of thread of the tap.