What I Learned Today — Taking Precision Tool Accuracy For Granted

What I Learned Today — Taking Precision Tool Accuracy For Granted

We often take for granted that a precision tool will always perform up to its expected standards. So, we were surprised one day when we casually decided to check the accuracy of our veteran height mic with a dial caliper only to discover that the height mic indicated a reading was in error by almost 0.012 inch. This isn’t a deal breaker by any means, but it was a bit of a surprise. Then we checked the accuracy of the dial caliper just for fun and it was within 0.001 inch of a quality standard that we know is accurate.

The point is, that over time, a precision tool can lose its accuracy so it’s best to regularly check them against a standard. This is especially true with micrometers and items like clicker-style torque wrenches. We performed a test a number of years ago with the help of a company that does Federal Aviation Agency (FAA)-certified calibration work. Cornerstone Metrology in Van Nuys, California did a test for us that showed a 5 lb-ft loss of accuracy when the wrench was left tightened at 70 lb-ft for three months. The wrench clicked at 70 lb-ft when in fact it had only torqued to 65 lb-ft.

Besides having a precision tool calibrated (or calibrating them yourself) on a regular basis, there are some preventative measures you can take to help maintain the accuracy of your tools. For example, with a click-style torque wrench, always return it to a very low setting like 10 lb-ft when sitting in your toolbox. With micrometers and calipers, make sure to store them in a place with as little humidity as possible and keep the measuring surfaces from touching each other while stored.

Digital torque wrenches are expensive, but several companies now make a digital torque adapter that fits in between a 1/2-inch drive breaker bar and the fastener you wish to torque. Generally, these adapters will display a series of lights or may emit an audible beep when the proper torque has been achieved.

About the author

Jeff Smith

Jeff Smith, a 35-year veteran of automotive journalism, comes to Power Automedia after serving as the senior technical editor at Car Craft magazine. An Iowa native, Smith served a variety of roles at Car Craft before moving to the senior editor role at Hot Rod and Chevy High Performance, and ultimately returning to Car Craft. An accomplished engine builder and technical expert, he will focus on the tech-heavy content that is the foundation of EngineLabs.
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