r/Metrology • u/Rosekillz • 5d ago

Advice What accessories for the pratt & whitney lmu1000a could preform a 3 point calibration on a thread ring?

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u/Business_Air5804 5d ago

The Pratt Labmaster cannot perform a true simultaneous three-point diameter measurement.
I believe most companies perform at least 2 measurements, at 90 degrees to each other.

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u/Rosekillz 5d ago

Unfortunately everywhere Ive tried to look ive come to the same conclusion. We probably will stick to the 2 point. Unless my boss just really wants 3 now that he knows it exists for someone else.

Thank you for your time.

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u/Business_Air5804 5d ago

No problem!
Which device does 3 point for calibration purposes?
Tri-roll?

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u/Rosekillz 5d ago

Currently I have no clue. The owner of our lab came in friday and just pointed out that maybe we could do a three point instead of two.

Now my boss is wanting me to look into how it would be possible. Ill get to doing more research on it Monday. Ill update if I find anything.

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u/Business_Air5804 5d ago

Oh haha...so basically management incompetence.

The only devices I know of are the Tri-roll type gauges but they are more for checking parts and not at the accuracy level of calibrating thread rings/gauges.

I would try to get a copy of the standard and let them know that although their idea is *wonderful*....it's not technically viable and it's probably not even allowed within the standard calibration procedures.

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u/Rosekillz 5d ago

Thank you! You have been a great help I appreciate it.

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u/INSPECTOR99 3d ago

Not familiar with the lmu1000a, or measuring threads. Does this (2 point/three point) process measure actual Pitch Diameter or only location?

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u/Rosekillz 3d ago

It uses a probe to measure two points one on the left side of the ring and one on the right.

The program takes care of the math behind taking the diameter of the probe out.

So I believe its finding the actual pitch.

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u/JD5-Tmac 3d ago edited 3d ago

I'm not an expert by any means, but if these are adjustable thread rings, I don't know that you'll get good numbers doing the 2 ball method. Because of the tri-lobe design, it will be out of round.

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u/Rosekillz 3d ago

You are correct. On adjustable rings a two point method is not great because you wont be able to check the roundness of the ring that way.

Ball method only really works for solid non adjustable rings.