A taper key is uniform in width but tapered in height. The bottom surface is straight and the top surface is tapered. Taper keys are often used with Gib head for easier removal of key during disassembly. When it's firmly driven, it acts to
prevent relative axial motion. Nominal dimensions of gib head are covered in ANSI B17.1-1967 standard and given in the following table.
Sunk Key: A standard form of key with rectangular or square cross-section in which the key fits into the keyseats on the shaft and the hub.