Buying guide · Printable checklist

Used Gage Buying Checklist: What to Check Before You Pay

A used gage is only worth buying if it still measures. A clean case and a famous brand don’t tell you that. This is the bench check to run on calipers, micrometers, indicators, height gages, bore gages, pins and thread gages, plus how to read the paperwork and when to walk away. Print it, bring a couple of gage blocks, or use the photo list to screen a listing remotely.

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

• Every gage
• Cal certs
• Calipers
• Micrometers
• Indicators
• Height gages
• Bore gages
• Pins & threads
• Blocks & plates
• Photos to ask for
• Walk-away list

1. Every gage, every time

• Brand, model, range, resolution or graduation, and serial number written down.
• Measuring faces looked at under light and magnification: no rust, pitting, chips, burrs or bright worn spots.
• No signs of a drop: bent frames, cracked dials, dented cases, crooked spindles.
• Original case and accessories present (setting standards, spanners, extensions, anvils).
• Tool has acclimated to room temperature before you judge tenths. A gage pulled from a cold truck reads differently.
• Zero checked, then at least one reading checked against a gage block or standard. Zero alone proves very little.

2. Reading a calibration certificate

• Serial number on the cert matches the serial on the tool.
• Calibration date noted. A cert is a snapshot of that day, not a promise about today.
• Lab name and whether the cal was accredited (ISO/IEC 17025 cert shows the accreditation body and certificate number).
• As-found and as-left data, not just “pass.” As-found tells you how far it drifted in service.
• Measurement uncertainty and the points actually checked are listed.
• A sticker with no matching cert is a sticker. Treat it as no paperwork.

For production or audited work, plan to have a used gage calibrated under your own quality system before it goes to the floor, cert or not. Budget that in before you agree on price.

3. Calipers (dial, digital, vernier)

• Close the outside jaws and hold them to a light: no visible gap along the jaws.
• Zero repeats after opening and closing several times.
• Jaw tips square and sharp, not rounded, chipped or ground on. Inside (ID) jaws not bent.
• Slide runs the full travel smoothly with no tight spots or rocking. Lock screw works.
• Dial calipers: needle doesn’t jump or skip, and the rack is clean with no damaged teeth.
• Digital calipers: no corrosion in the battery bay, display steady, zero and unit buttons work, no lost count when you move the slide quickly.
• Read a gage block near the start, middle and end of the travel.
• Depth rod straight and flush with the end of the beam at zero.

4. Micrometers

• Anvil and spindle faces clean and undamaged; carbide faces not chipped.
• Close with the ratchet or friction thimble and check zero. Larger mics (over 1" / 25 mm) need their setting standard. Missing standard is a price point.
• Spindle turns smoothly over the whole range with no tight spots and no side play.
• Ratchet or friction thimble slips consistently; spindle lock holds without shifting the reading.
• Readings checked against gage blocks at several points across the range, not only at whole turns.
• Frame not sprung. If faces can be checked with an optical flat, the bands tell you about flatness and parallelism.
• Sets: every frame and standard present and matched, not a mixed set sold as complete.
• Full walkthrough, including optical-flat checks and when re-cal isn't worth it: buying used micrometers.

5. Dial and test indicators

• Plunger (or stylus) moves smoothly through its travel and the needle doesn’t stick or hesitate.
• Repeatability: lift and release onto the same surface several times. The reading should return to the same mark.
• Revolution counter tracks the main needle; bezel turns and locks.
• Contact point present, tight and not worn flat. Test-indicator stylus straight and the right length for that model.
• Crystal not cracked; stem and back not bent (a bent stem means it was dropped or forced).

6. Height gages

• Base underside clean and flat. Set it on a surface plate: it should not rock.
• Column free of dents; slider moves smoothly, fine adjust works, locks hold.
• Scriber or probe intact; carbide scriber tip not chipped.
• Zero on the plate, then check gage-block stacks at a few heights through the range.
• Electronic height gages: powers up, probing functions work, charger or power supply included, air float works if equipped.

7. Bore gages

• Dial bore gages: full set of anvils, extensions and washers present; centralizing guide works; plunger smooth.
• Indicator included, and it is the one that belongs with the gage.
• Three-point internal micrometers: setting ring(s) included. The rings are often worth as much as the heads, so confirm them in writing.
• Reading repeats when set in a ring or a mic set to size, several times in a row.

8. Pin gages and thread gages

• Pin sets: count the empty slots. Sizes legible; tolerance class and plus/minus marked on the case or cert.
• Spot-check a few random pins with a micrometer; look for rust, nicks and bright wear bands at the ends. Full walkthrough, plus classes and plus/minus: pin gage set guide.
• Thread plugs: GO and NOGO members both present, markings legible (size, pitch, class such as 2B or 3B), members tight in the handle. What the class means and how to check a used plug: thread plug gage 2B vs 3B.
• Thread rings: adjustable rings still have their lock screws and sealant intact. Broken seals mean someone adjusted it.
• Thread wear can’t be judged by eye on a bench. Thread gages need a lab check (setting plugs, thread wires) before you trust them for acceptance. Price accordingly.

9. Gage blocks and surface plates

• Gage block set complete against the case layout; grade marked on the case or cert.
• No rust, staining or burrs on the gaging faces; clean blocks still wring. Grades, the 81-piece layout and the full bench check: used gage block set guide.
• Granite plate: chips at the edges are common; chips, pits or worn hollows in the working area are not. Tag, stand, the repeat-reading screen and the six photos to ask for: used granite surface plate guide.
• Plate grade and last flatness check noted. A plate that has been moved should be checked again where it will sit.

Remote screening: the 8 photos to ask for

1. The whole lot or case open, every piece in view
2. Brand, model, range and serial markings
3. Measuring faces close up (jaws, anvils, spindle, scriber, contact point)
4. Zero reading with the tool closed or on its standard
5. A reading on a gage block, with the block size visible
6. Any cert page showing serial and date
7. Close-ups of rust, dents or damage
8. For sets: the case layout with empty slots visible

If a seller won’t shoot those, you are buying blind. Price it as unknown or pass.

Buy, renegotiate or walk

Rule of thumb: if the savings versus new don’t cover a calibration plus any missing standards or accessories, buy new or keep looking.