The Pitch Diameter of Pipe Taper Thread Measurement and Uncertainty Using Three-Wire Probe

The pipe taper thread measurement and uncertainty 
normally used the four-wire probe according to the JIS B 0262. 
Besides, according to the EA-10/10 standard, the pipe thread could be 
measured using the three-wire probe. This research proposed to use 
the three-wire probe measuring the pitch diameter of the pipe taper 
thread. The measuring accessory component was designed and made, 
then, assembled to one side of the ULM 828 CiM machine. 
Therefore, this machine could be used to measure and calibrate both 
the pipe thread and the pipe taper thread. The equations and the 
expanded uncertainty for pitch diameter measurement were 
formulated. After the experiment, the results showed that the pipe 
taper thread had the pitch diameter equal to 19.165mm and the 
expanded uncertainty equal to 1.88µm. Then, the experiment results 
were compared to the results from the National Institute of Metrology 
Thailand. The equivalence ratio from the comparison showed that 
both results were related. Thus, the proposed method of using the 
three-wire probe measured the pitch diameter of the pipe taper thread 
was acceptable.

• J. Kloypayan
• W. Pimpakan

• Pipe taper thread
• Three-wire probe
• Measure and Calibration
• The Universal length measuring machine.

[1] JIS B 0262, "Measuring Method of Pitch Diameter of Taper screw Plug
Gauge and Inspection.” JIS Handbook, pp.187-206, 1998.
[2] ISO 7-1, "Dimensions, Tolerances and Designation,” Pipe Thread
Where Pressure-Tight Joints are Made on the Threads, 1994.
[3] EA-10/10, "Guidelines on the Determination of Pitch Diameter of
Parallel Probing,” EA European Co-Operation for Accreditation,
1999.
[4] EA-4/02, "Expression of the Uncertainty of Measurement in
Calibration,” EA European Co-Operation for Accreditation, 1999.
[5] Thomas M. Adams, "A2LA Guidelines for the Estimation of the
Uncertainty of Dimension Calibration and Testing Results,” 2002
[6] J. Kloypayan, W. Pimpakan, "Measuring Accessory Component Design
and Analysis for Taper Thread Measurement,” International Congress
on natural Science and Engineering, pp. 180-186, 2013.
[7] J. Buajarern, K. Naoi, "Asia Pacific Metrology Program
Intercomparison of high precision Roundness measurement,”
APMP.L-S4 Roundness intercomparison Protocol, Version 3, pp. 16,
2012-2013.