In “The Twits,” a short story by Roald Dahl, Mr. and Mrs. Twit, a disagreeable older married couple, play a series of nasty pranks on each other. One of these tricks is particularly illuminating for manufacturers and repair shops relying on torque tools to properly assemble products or handle maintenance jobs.
To get back at Mrs. Twit, Mr. Twit glues a piece of wood no thicker than a penny to the bottom of Mrs. Twit’s cane and chair. Since the pieces of wood are so small, Mrs. Twit doesn’t even notice the difference. Mr. Twit repeats this process night after night, gluing on piece after piece of wood. Soon enough, Mrs. Twit’s feet won’t touch the floor when she sits in her chair, and her cane goes halfway up to her shoulder. Naturally, Mr. Twit informs her that the cane and the chair can’t be growing—the only explanation is that Mrs. Twit is shrinking! He convinces her of this so thoroughly that she agrees to be tied to 100 balloons in the front yard in order to stretch her back out.
So, what does this have to do with manufacturing or repair? Well, what Mr. Twit knew was that when change is gradual, it can be very difficult to notice (pretty smart for a twit). As you use your tools, day by day, they can slowly slip out of alignment so gradually that you won’t notice it until the next time you test them for calibration. If you only test your tools once every six months, then your tools may have been applying increasingly incorrect amounts of torque to every fastener they’ve tightened for the last half a year. This can lead to faulty products, inaccurate repairs, and exposure to liability. To prevent this gradual slippage, it’s important to routinely use a torque sensor to keep your tools calibrated.
Frequent Calibration Testing Prevents Inaccurate Fastening
Keeping tools in calibration requires frequent testing. This is not because tools frequently go out of calibration—high-quality tools are designed to hold their values for extended periods, up to months or years. Instead, it’s because when tools do go out of calibration, it’s difficult to notice.
Each fastener tightened with an improperly calibrated tool will be too loose or too tight, running a higher risk of failing in the field. The farther out of calibration the tool is, the higher the risk. The longer a tool goes between calibration tests, the more fasteners may be tightened incorrectly.
Routine calibration testing can be fast and simple, which is good news for managers worried about tool downtime and laboratory fees. Torque sensors and torque analyzers are simple, benchtop devices designed to rapidly inform employees if the tool they’re testing meets calibration standards.
Modern Torque Testers Allow for Rapid Daily Calibration Tests
Modern torque testers, which combine sensors and analyzers, are small and easy to use. An operator selects a test torque amount on the device, sets their tool to deliver that same amount, then applies torque until their tool shuts off, clicks, deflects, or slips. The torque tester displays a pass/fail indication, such as a green or red light.
To ensure accuracy, tool operators can perform the test several times in a row. If they see three green lights in three tests, for instance, then they know they’re good to go. If a tool fails, then they can flag it and remove it from service to be recalibrated. Since this entire sequence takes less than a minute, it can be performed daily without losing productivity.
Little changes can add up to big trouble—just ask Mrs. Twit. When tools slip out of calibration, they often do it so gradually that it’s difficult to detect until it’s too late. However, by testing your torque tools regularly, you can significantly reduce the risk of inaccurate fastening. The size and simplicity of modern torque testers allow operators to test calibration quickly and effectively. Knowing your tools are in calibration, every day, provides peace of mind and a promise of reliability that you can promote to your customers.
