Fourteen years—maybe thirteen and a half, I'd have to check my records—and somewhere north of $200,000 in metrology purchases. That's the short résumé behind what I'm about to say. The biggest mistake in precision measurement is not the brand you choose; it's forgetting that every tool's accuracy is a promise, not a guarantee. A FARO CMM arm, a C5 compact thermal camera, a good microscope, and a pair of calipers can all fail you quietly, and usually at the worst time.
I'm the quality manager at a mid-size contract manufacturer. I've personally made—and documented—enough expensive mistakes to fill a binder. The most painful one cost $3,200 and a one-week production delay. So now I maintain a pre-check list for every measurement item we own. That list has saved us more money than any single tool purchase.
Why I started writing things down
In my first year, 2017, I signed off on a FARO CMM arm because our QC lead said we needed it. He wasn't wrong—the arm was the right answer for large aluminum frames. But I never set up a calibration reminder. In September 2022, a routine check showed the arm's readings drifting. FARO's service report said the compensation date was overdue. That mistake cost $3,200 in rework plus a week of missed deliveries.
I didn't fully understand the value of a calibration schedule until that order came back completely wrong. What I learned is that a FARO CMM arm is not a 'set and forget' instrument. It's a device with a memory. If you don't track its calibration, it will happily tell you lies with three decimal places.
When I compared our Q1 and Q2 inspection logs side by side—same arm, same operators, but one after proper calibration—I finally understood why the details matter. We had been catching errors, but only after they cost us. Put another way: the arm was doing exactly what it was told. We were the ones failing the part.
What a FARO CMM arm is actually for
A FARO CMM arm solves a specific problem: dimensional measurement of parts that are too large, too awkward, or too difficult to move to a traditional CMM. It's portable, flexible, and sensitive to operator technique and environmental temperature.
Before you buy one, ask these three questions:
- What is the largest tolerance you need to inspect? If it's under 0.0005 inches, a portable arm is probably the wrong tool. A fixed CMM or a dedicated gauge is better.
- How much operator training are you willing to pay for? A FARO arm is easy to learn, but measuring correctly takes practice.
- Who will calibrate it, and when? The answer should be written down before you order.
If your parts are bigger than a car door and measured in meters, a FARO laser tracker might make more sense. That's a different investment—and a different calibration schedule. Don't combine the two in your head.
The old thinking goes, 'If it ain't broken, don't calibrate it.' That mindset comes from an era when mechanical instruments stayed put. A digital FARO arm has probes, encoders, and temperature sensors that can degrade without visibly breaking. It's not the same world.
The C5 compact thermal camera is not a CMM
The first time someone asked me about the C5 compact thermal camera, I rolled my eyes. A thermal camera in a metrology shop? I thought it was a gimmick. Then we used one to find a failing spindle bearing before it turned into a $12,000 repair. That changed my mind.
The FLIR C5 compact thermal camera doesn't measure dimensions. It won't tell you if a hole is in the wrong place. What it does is point you toward problems that affect measurement: electrical hot spots, overworked motors, bad connections. It's a diagnostic tool, not a precision measuring tool. The mistake is to treat it as an alternative to a FARO CMM arm. It isn't.
In our workflow, the C5 comes out when the CMM readings look odd. It helps us find the 'why' before we start adjusting variables.
Don't forget the microscope
It's easy to be seduced by big-ticket items. But a microscope is one of the most useful inspection tools we own. A basic stereo microscope lets you see burrs, edge breaks, and micro-cracks that calipers can't detect. It costs a fraction of a CMM arm, and it never needs software updates.
If you're setting up a quality lab on a budget, buy the microscope before the second thermal camera. You'll use it more than you expect. I know we do.
Starrett vs Mitutoyo calipers: the debate that never dies
Now to the question that shows up in every forum: Starrett vs Mitutoyo calipers? I've owned both. I still use both today. Here's the honest answer: out of the box, measured against a calibrated gauge block, both are within their published tolerances. The real differences are feel, digital output, and after-sales support. Starrett has a heavier beam; Mitutoyo's IP67 models handle coolant better. Choose the one that feels right, and then put it on the same calibration schedule as everything else.
Per FTC guidelines (ftc.gov), a vendor's performance claims must be substantiated. But even a substantiated claim doesn't account for the day your caliper gets knocked off the bench. Your own calibration process is what catches that. Don't rely on the logo.
Where this breaks down
This system works because we are a mid-size job shop with a stable product mix. If you're in aerospace, medical devices, or regulated contract manufacturing, your rules will be stricter. Calibration intervals may be shorter. Documentation requirements may be federal or customer-specific. My point isn't that every shop should copy my checklist—it's that every shop needs one.
Since we built the checklist, we've caught 47 potential errors before they left the shop. I still get tempted by the next shiny tool. The difference is that now I ask the same question first: how long will it hold its accuracy, and how will I know? That question has saved me more money than any brand loyalty or spec-sheet comparison.
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