GearWrench 388708N 1/4 x 28 NF Taper Tap The GearWrench 388708N 1/4 x 28 NF Taper Tap features tapered cutting edges, which give a less aggressive cut than plug taps in small diameters. Manufactured from carbon steel, the GearWrench 388707N 1/4 x 20 NC Taper Tap has clear laser-etched size markings for easy identification.