Some Serious Issues with Torque Wrench Calibration
Posted by Phil WisemanAug 20, 2020 8:29:48 AM
6 minutes to read
Do you calibrate torque wrenches?
I was recently asked this question and the answer is yes. As is the case with all ISO 17025 accredited laboratories we do have limitations based on our scope of accredited services. In this specific case, the range was within our capabilities.
Companies change calibration services for a variety of reasons.
I asked specifically if they were having any issues with their current calibration service.
" Every time we get our torque wrenches back from calibration, I get complaints that they are not reading properly."
Interesting response so I asked if I could review their calibration certificates. Upon review several serious issues with their torque wrench calibration were discovered.
Torque Wrench Resolution
Resolution is the smallest change that can be detected.
As an example this company had a 600 ft lb torque wrench with a stated resolutions of 0.1ft-lbs.
There is often confusion between Resolution and Accuracy.
Imagine if you zoomed in on the image above and there were markings/subdivisions instead of just one big red dot bullseye. That is one way to think of resolution.
"The diagram in Figure 5.1 shows the same position (the point in the center of the bullseye) measured by two instruments. The two grid patterns represent the smallest objects that can be detected by the instruments. The pattern on the left represents a higher-resolution instrument."
Phil Wiseman is Chief Marketing Officer at Alliance Calibration. He earned a B.S. in Chemical Physics from Centre College. Phil is an ASQ Certified Quality Auditor and ASQ Certified Manager of Quality/Organizational Excellence.
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