P.D. = Pitch Diameter
M = Measurement over wires
W = Wire diameter
C = Constant
C = .86603 x Pitch (inches) -3W
P.D. = M-C
W = .57735 x
Thread Measuring Wires
Tolerance and specifications:
- within .000020 of best wire diameter for specified tpi.
- within .000005 of the calibrated size provided on label.
- have the same diameter within .000005.
- roundness within .000010.
- taper does not exceed .000010.
- standard 2 lengths.
- minimum hardness of RC 62.5.
- surface finish lapped, 1 MU AA.
- traceable to NIST.
- wires meet or exceed Federal specifications ASME/ANSI B1.2 and B1.6M for Grade A Master Thread Wires
Use of best size wires
In measuring screw threads it is desirable to use wires which touch the thread at or near the pitch diameter for the reason that with such Best Size wires the measurement of pitch diameter is least effected by an error in the included angle of thread.
Notes: Maximum and minimum wires should be used which are safely within the limiting dimensions given by the above formulas.
Call for information and pricing of special wire diameters including Whitworth, British Association, Buttress and worm threads.
Root Diameter Wires:
60° and 55° threads from 41/2-64 TPI.
Price per set of 3 wires.
Call for prices.