taylortools

Standard System of Tap Marking
Taps, Dies and other types of threading tools are marked according to the Standard System of Marking
Ground Thread Taps. The tools are marked with the nominal size, number of threads per inch (pitch),
and the appropriate thread form symbol and pitch diameter symbol. Symbols typically used are listed
below.
Thread Form Symbol
Nominal Size – Lead of the Tap
Tap Material
Pitch Diameter Limit
V 1.0 – November 2011 Page 171