Buying guide · Printable checklist

What to Look for When Buying a Used CMM

A used coordinate measuring machine is a granite structure, an air system, a probe, a controller and a software license. The granite is usually the part that survives. The controller, the license and the move are where used-CMM deals go wrong. This checklist covers what to confirm before you pay, the test to run at the machine, and the questions a listing won’t answer for you.

Print this checklist Ask about a CMM: 508-343-1219

• What you’re buying
• Software & license
• Air bearings & air
• Granite & scales
• Repeatability test
• Verification report
• Moving it
• Photos to ask for
• Walk-away list
• FAQ

1. Know exactly what you’re buying

• Maker, model, serial number and year written down from the machine’s own plate, not the listing.
• Measuring volume (X, Y, Z travel) fits your largest part plus fixturing, with room to reach every feature.
• Type: manual or DCC (computer-driven). A manual machine and a DCC machine of the same size are not the same purchase.
• Probe head identified: fixed, manually indexed, or motorized indexing, and touch-trigger or scanning. Stylus kit and probe modules included.
• Controller make and generation noted. Ask whether parts and service are still available for that controller.
• Joystick or jog box, PC, monitor, cables, reference sphere and any rotary table or fixture plate included, listed in writing.

2. Software and license transfer

• Software name and exact version recorded. Ask whether it can import the CAD formats your customers send.
• License key, dongle or license file is with the machine. No license usually means buying one.
• The software maker’s transfer policy confirmed in writing. Some allow transfer to a new owner, some charge for it, some require a new license.
• The PC boots and the software opens with the machine connected. An old operating system can limit what you can run and network.
• Existing part programs, probe files and backups offered (with any customer data removed).
• Software maintenance status asked about. Lapsed maintenance can mean a fee to update.

This is the section to settle before anything else. A clean machine with a license you can’t use is a project, not a measuring machine.

3. Air bearings and air supply

• Air on: each axis floats and moves smoothly by hand or joystick with no grabbing, rubbing or uneven spots.
• Bearing surfaces and the guideways they ride on looked at with a light: no scoring, scratches or rubbed tracks. Marks there can mean a bearing touched down.
• No hissing leaks at fittings, hoses or the bearing pads.
• Air regulator, filters and gauge present; ask what supply pressure and air quality the maker specifies.
• Ask how the shop’s air was dried and filtered. Oil or water in the air is hard on air bearings.

4. Granite, structure and scales

• Granite table: edge chips are cosmetic; chips, cracks or pits in the working area are not.
• Threaded inserts in the table are intact and not stripped. You’ll need them for fixtures.
• Bridge or column shows no impact damage. Covers and bellows are present and not torn.
• Scales are clean and undamaged where you can see them. Don’t wipe them yourself; ask the seller.
• Temperature sensors and compensation (if the model has them) are connected and reading.

5. Run it: the repeatability test

• Machine powers up, homes every axis and shows no errors you can’t explain.
• Probe qualifies on the reference sphere, and the qualification result looks consistent when you repeat it.
• Measure the same gage block or sphere several times at the center of the table. The readings should repeat closely.
• Move the same artifact to each corner of the measuring volume (and up in Z if you can) and measure again. Corners are where a machine that is out of geometry shows it.
• Compare center and corner results with the artifact’s known size. A machine that repeats but reads off at the corners needs geometry correction, not just a probe check.
• If you need it, measure a real part feature you care about: a bore, a flatness or a true position.

This isn’t a formal calibration. It tells you whether the machine is healthy enough to be worth calibrating.

6. Paperwork and the verification report

• Most recent performance verification report (ISO 10360-2 or ASME B89.4.10360.2) requested, with the date and who did it.
• The serial number on the report matches the machine.
• Service history: bearing, controller or probe repairs, and why.
• Manuals, wiring diagrams and the original configuration or error-map files, if the seller has them.

For audited or customer acceptance work, plan to have the machine verified in its new location under your quality system no matter what the old report says.

7. What the move really involves

• Shipping locks or brackets for the bridge, carriage and probe head are present. Moving a CMM without them risks the bearings and the structure.
• A rigger who has moved CMMs before is booked. Granite is heavy and cracks if lifted wrong.
• The new room is ready: stable temperature, no direct sun or HVAC blast, a solid floor away from presses and forklifts, and clean dry air.
• Leveling, settling time and a post-move verification are scheduled and budgeted.
• Get quotes for rigging, transport and the post-move verification before you agree on a price, not after.

Remote screening: the 8 photos to ask for

1. The whole machine with the PC and controller in view
2. The machine data plate with model and serial
3. The probe head and stylus kit
4. The granite table surface, including any chips
5. Close-ups of the guideways and bearing surfaces
6. The software’s About screen showing version and license
7. The latest verification report page with serial and date
8. A short video of each axis moving under power

If a seller can’t show the software running or the machine moving, price it as parts or pass.

Buy, renegotiate or walk

Rule of thumb: add the license, rigging, room prep and post-move verification to the asking price. If that total doesn’t beat the alternatives, keep looking. The used CMM price guide has a full total-cost worksheet.

Used CMM questions

What is the most important thing to check on a used CMM?

Whether the software license and controller come with it and still run. A sound granite bridge with a dead controller or a license that won't transfer is a long, expensive project, not a machine you can measure parts on next week.

How do I test a used CMM before buying it?

Home every axis, qualify the probe on the reference sphere, then measure the same gage block or sphere several times at the center of the table and at each corner of the measuring volume. The readings should repeat closely and agree with each other. Ask for the most recent ISO 10360-2 or ASME B89.4.10360.2 verification report as well.

Does a used CMM need to be recalibrated after it is moved?

Plan on it. Moving a CMM can shift its geometry, so it should be leveled where it will sit, given time to settle to the room temperature, and then verified before you rely on it for acceptance.

Can the software license on a used CMM be transferred?

It depends on the software maker. Some transfer a license to a new owner and some charge a fee or require a new license. Get the license key or dongle, the exact software version and the maker's written transfer policy before you agree on price.

Is it cheaper to buy a used CMM or send parts out for inspection?

It depends on how many parts you inspect. If you only need a few first-article packets or spot checks a month, contract CMM inspection can cost less than buying, moving, verifying and staffing a machine. Run your real numbers both ways.