Calibration Services Done Right: Hiring a Pro vs. Handling It in House

Even the best, most expensive metrology equipment is unreliable if it’s not calibrated correctly.

Getting the tools and staff to do that in-house, however, is beyond the budget of many smaller machine shops—and not necessarily the best choice even for larger ones.

Whether it’s better than hiring an outside company to handle calibration “really depends on the company, the skill level of their quality control people, the number and types of measuring tools they use, and how often they have to get them calibrated,” says Jim Salsbury, senior vice president of quality and services at Mitutoyo America Corp. in Chicago.

In a recent interview with Better MRO, he discussed developments in metrology during 25 years with the company, the trends shaping the field’s future and what businesses need to do to ensure their metrology tools are accurately evaluating whether machined workpieces meet client specifications.

Better MRO: When I started in manufacturing, the inspector would come around once a year and grab your micrometers and other hand tools, then bring everything back a couple of hours later with a calibration sticker on them. How is that responsibility handled by most of your customers today?

Salsbury: It’s really a mix. We train a lot of people here on everything they need to calibrate in-house, but at the same time, we provide a broad array of calibration services. It really depends on the company, the skill level of their quality control people, the number and types of measuring tools they use, and how often they have to get them calibrated.

Better MRO: Let’s say you own a small machine shop. Give us some examples of what you would tackle on your own.

Salsbury: As a general rule, it’s what you said a moment ago—micrometers, calipers and so on. Calibrating those in-house is pretty easy. You don’t need a special facility and you don’t need very expensive equipment: A set of high-quality, traceable gage blocks will take care of most of it. When you move into height gages and indicators, though, you start getting into more expensive equipment and tighter temperature controls. For instance, you could spend $10,000 for a good indicator tester, and if you want to check your pin and plug gages in-house, about the same amount of money for a laser-scan micrometer. Some of these might not make financial sense until the shop reaches a certain size.

Gage Block Calibration

Better MRO: Let’s flip the question around. What types of measuring equipment should a smaller shop avoid calibrating on its own?

Better MRO: What do you mean by “Do what they say they’re going to do?” Isn’t that guaranteed if they are accredited?

Salsbury: Maybe, but then again, maybe not. I’ll give you an example. One of our customers bought a linear height gage that is roughly 10 times more accurate than competing products. They sent it out to a third-party lab, which declined to certify it. Why? Because the tools they were using to calibrate the gage were less accurate than the gage itself. Unfortunately, this kind of situation is becoming more common, which is why manufacturers must verify in advance that their calibration partner can meet their requirements—and in the worst case, make sure that any reported measurement uncertainty is smaller than the tolerance that’s being checked.

Better MRO: If a shop’s calibration provider needs accreditation, doesn’t the shop itself? And if so, what’s involved?

Salsbury: Maybe not yet, but I think it’s coming. We’re starting to see some organizations requiring in-house labs to be accredited, although they still seem to be on the fringe. It’s definitely something to keep an eye out for since I can tell you that getting accredited would be a heavy lift for a smaller company. We’ll just have to wait and see. For now, the only thing that’s changed over recent years is that—generally speaking—whatever third-party calibration lab you use must be accredited.

How does your shop handle metrology equipment calibration? Tell us in the comments below.