Even a skilled and careful technician can be undone if their tools, such as torque wrenches, aren’t properly calibrated, which is why shop managers need to have a plan in place to verify that each piece of equipment is receiving regular checkups.
Not all tools in the shop require calibration, but technicians and supervisors need to know which ones require regular calibration to ensure repairs and replacements remain accurate in measurement, performance, and reliability. This includes everything from torque wrenches and pressure gauges to diagnostic equipment like multimeters and oscilloscopes.
“Calibration is important for any precision instrument,” explained Kevin Rohlwing, chief technical officer for the Tire Industry Association. “If measurements are incorrect, then the perceived solution may not solve the problem.”
It’s important to remember some tools, like torque wrenches, can become out of calibration through daily wear or from being dropped.
“When tools lose accuracy due to wear, mishandling, or environmental factors, the results can be catastrophic—and costly,” warned Justin Franchuk, office and HR manager at Team Torque, which tests, repairs, and calibrates various torque tools. “When your tools fail to deliver the correct torque, you’re playing a dangerous game with both product integrity and human safety.”
For example, over- or under-tightened wheel-end lug nuts can and have caused entire wheels to slip off many a truck and trailer on the road, leading to serious injury and death.
Wheel-off events happen “on average about three times a day somewhere here in North America,” said Rod Imhoff, key account manager at Chicago Pneumatic. “Now, granted, it normally goes off into a cornfield or the woods and we don’t need to hear about it, but it’s those times when it does hit some private property, a car, a building, or God forbid, a person, and you actually have a fatality.”
He added that “a fatality can be complete bankruptcy to a company that owned that vehicle when [the wheel] came off.”
But being mindful of torque wrench accuracy can ensure that these events are mitigated.
Read more: Runaway rubber wrecking balls: How proper pre-trips stop wheel-offs
How tools become uncalibrated
Torquing to a specific calibration level means stretching a stud just enough to where it wants to return to its original yield point, Imhoff explained.
“When you exceed that and you go too high, you can stretch that stud beyond a yield point; visibly, you may not even notice it, but you would certainly notice it over time,” he said.
He likened the situation to wearing a tube sock. “You might get up and put your tube sock on, and it goes up to about mid-calf, and it’s fine. But by lunchtime, it’s falling down around your ankle,” he illustrated. “Now, why is that? Because it was stretched beyond its yield point at some point.”
While over-torquing can stress a lugnut, leading to it cracking and not doing its job to keep the wheel attached to the spindle, Rohlwing said it’s more common for an imprecise wrench to not provide enough torque.
“When torque control devices go out of calibration, it usually means the actual torque is less than whatever the tool is set for,” he said. “If they are dropped, improperly stored, or damaged, the end result may not be accurate.”
Torque & torts
Whatever the case, when a wheel off causes injury or death, the last shop recorded to have touched that wheel will face severe scrutiny in court.
“In the event of a wheel-off accident, the plaintiff’s lawyer will consider everything that may have contributed to the accident,” Rohlwing explained. “Was the technician properly trained to install the wheel with the correct torque and clamping force? Did they follow industry-recommended practices? Was the torque control device calibrated? Is there a certificate of calibration to verify the accuracy?”
Read more: Tips to choose, use, and maintain torque wrenches
Rohlwing has seen this kind of interrogation firsthand as an expert witness.
“I’ve been in civil cases where these types of questions are always asked,” he recalled. “An untrained technician who doesn’t follow industry guidelines and uses a torque control method that has never been calibrated is difficult to defend,” he cautioned. “The reverse is also true in that a well-trained tech that follows the guidelines and uses a calibrated torque control device is easier to defend.”
Tracking tool checkups
Regular tool calibration is the remedy, but an effective calibration program requires an understanding of which tools require calibration and how often. This information almost always comes directly from the manufacturer.
To keep track, shops should assign a designated person or team responsible for keeping these tools in spec.
Dillon Grimes, a mobile diesel mechanic for Cox Automotive, explained that it’s a bit of a joint effort where he works. Whereas the company itself is responsible for keeping torque wrenches and other similar tools calibrated, the responsibility for air and tire pressure gauges falls to the technicians themselves.
“Whenever [a gauge] shows sign of wear, you test it against two or three different devices,” he said, “and if it registers differently, then we either recalibrate or replace those.”
DJ Painter, a former technician and now Noregon technician as a service lead, advised management to ensure all relevant shared shop tools are calibrated annually and to red tag those that aren’t. To motivate techs to also keep their personal tools calibrated according to schedule, he suggested using an incentive program.
Grimes explained that ensuring some devices are calibrated can be easily incorporated into typical repair processes without expending too much extra time.
“Every so often, I’ll go out of my way and instead of just the normal air pressure gauge I use, I’ll grab two just to verify that they’re both reading correctly.”
Many newer tools let you know when they require calibration, like the CP86 series from Chicago Pneumatic. While users should still get the tool calibrated on an annual basis or per manufacturer guidelines, these smart tools will alert you if something changes via an app on a cell phone or tablet that allows monitoring.
“If you use the tool on really high-level torques, or maybe you use the tool frequently enough, or you drop the tool, it records all of that kind of information and does its own algorithm to figure out when calibration is due,” Imhoff outlined.
For other tools, this isn’t always possible or practical, especially if the intricacies of the tool demand a higher attention to detail.
“When you think about pneumatic tools, calibration is more than just making sure it’s torquing properly,” Imhoff explained. “It’s ensuring that the rings, springs, and valves are working appropriately too. So there are some parts that can have some wear and tear and need to be replaced regularly as well.”
There are other factors that make taking care of regular calibration in house a less-than-ideal solution.
“A lot of companies will put stickers on their tools when calibration is due, but let’s call it what it is,” Imhoff remarked. “[A shop] environment is not the best for stickers to stay on things the way they should. It’s a greasy, oily environment with a lot of different cleaning chemicals and things, so it doesn’t really work so well.”
All that said, the safest way to stay on top of your calibration and ensure that your tools are holding up their end of the bargain is to regularly schedule them as per OEM guidelines.
Imhoff recommends outsourcing to a reputable third-party company instead of investing in calibration equipment and training in-house.
“If you can get a company that’s going to do an annual calibration—I call it a birthday card—they’ll send you a reminder that it’s coming up on your annual time to get calibrated,” he concluded. “That’s the best way to do it.”
