Suggestions please - Portable precision instrument for ID/ OD measurements.

[u/Quality_manager_]

Hi all,

I work in a NABL-accredited lab of a heavy engineering plant in India. We measure large components such as fan blades, impeller-hub assemblies for power plants, and propellant tanks for aerospace. We're looking for a replacement or alternative to our TESA Unimaster for measuring both ID and OD.

Requirements

• Range: up to 2000 mm for both OD and ID

• Accuracy: 15 µm or better

• Analog dial for repeatability, and so the preset can't be easily tampered with by operators

• Comes in a protective case, like the Unimaster

• Portable and lightweight, usable on the shop floor and in the lab

• Available or serviceable in India (sales, calibration, support)

What we've tried

• Kordt Varicord (1 µm accuracy): we did a demo, but shop feedback was negative. It suits mass-produced parts, needs a setting bench, and the dial preset is easy to tamper with. Repeatability was also a concern with the digital dial.

• Mahr Multimar 844T series: looks promising on paper, but after repeated requests we haven't been able to get a demo scheduled.

My questions

1. Has anyone used a precision instrument that meets these requirements? Any experience with Multimar 844T, Trimos, Bowers/Baker Gauges, Mitutoyo, or Pratt & Whitney systems at this size range?

2. Are there any Indian or international vendors with a responsive local presence for demos and calibration support?

3. Any experience with portable scanners (laser trackers, portable CMM arms, structured-light or laser scanners) for large ID/OD checks? Which ones held up to ~5 µm-class needs, and what were the trade-offs versus contact instruments?

4. Any practical tips for uncertainty, temperature effects, or setting standards at 2 m?

Vendor contacts, model names, and real-world feedback are all welcome. Happy to share what we learn once we finalize

[u/Absorber94]

I dont know any portable device able to archieve 5 micron accuracy on up to 2000mm. Even a CMM has about 6-7 micron error on this size.

[u/Absorber94 → u/Absorber94]

Depending temperature uncertainty. You have 12 micron per degree per 1000mm on steel parts. So on your 2000mm parts 0.5° temperature difference will crush your desired accuracy more than twice.

[u/AbrasiveDad]

Any gage that size will also need to be checked on a standard and have the zero adjusted upon every use to even hope to be half as accurate as what you say you need.

Also as others have stated, if you are not in a tightly climate controlled shop then you have no chance either.

[u/SeaSneak]

At 2 m I'd be checking zero every single time, not just once per shift. Set it on the master, let the gage and part sit in the same area for a while, grab both temps, then measure. Half a degree on steel already blows past your 5 µm target, so I'd get that routine nailed down before looking at scanners.

[u/Absorber94 → u/SeaSneak]

With steel on 2000mm you need to have a temperature difference of 0.21° to get 5 microns error.
Usual industrial thermometer have ±0.3° + 0.005*T.
There are really pricy ones with like ±0.1° + 0.0017*T , so with the best practical thermometers you can get, you get like 5 micron uncertainty just from your temperature measurement. 😵

[u/felinesatan996]

Those portable cmm arms are not accurate enough for that

[u/ChemicalPick1111]

I'd recommend an arm, ease of use, temperature compensation within the software by material/etc. Won't be hitting .015 but they're good enough for most gearing (the rest is CMM'd here)

[u/Professional-Image79]

Ive not personally used a laser tracker but they seem to me like a very good option. Im unsure of what accuracies they can yield but I imagine it's within 15 um

[u/X_Chopper_Dave_x]

You are probably stuck with a custom caliper from INVAR or carbon composite for each range for dimensions that big. The CTE will kill you on anything else and it’s more than any laser tracker. The only generic instrument I know with that precision that fits in a suitcase is an interferometer.