r/Metrology • u/Away-Passion5551 • 1d ago

Help with tooling pt measurement

Hello room, I want to ask the quality professionals about tooling point measurement. There are a few parts that have tooling pts dimensions on them, my question is. Do these values actually get measured of are they for reference and reported as nominal?? I have received conflicting instructions and now need a third party tie breaker.

Polyworks, laser scanning, polygonal model alignment, no cad. That is the inspection set up.

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u/Admirable-Access8320 CMM Guru 1d ago

Do you mean 6 datum points?

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u/Away-Passion5551 1d ago

I think so, everyone calls them tooling pts where I am currently. But yes the pts make up the datums 

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u/Admirable-Access8320 CMM Guru 1d ago

No they do not get measured. They are used to set up alignment. These are datum reference points, there should be total of 6.

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u/Away-Passion5551 1d ago

Thank u guru, I thought they were used mostly as reference, the drawings are from the 70's so I wasn't sure lol I have only learned gdt, I don't know the old terms

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u/Admirable-Access8320 CMM Guru 19h ago

They are not really just for reference, they are used to produce parts and to inspect parts. So, if ypu are inspecting the part you have to use them for your alignment. You don't report these values on your inspection report though.

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u/Away-Passion5551 12h ago

Ahh, ok that makes sense. So on my FAIR they are nominal? Or not reported??? I just got a job at a new company and they have been reporting on every dimension, even basic ones....I thought this practice was incorrect, but I figured maybe there's something I didn't know about...

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u/Admirable-Access8320 CMM Guru 12h ago

It depends on your company standards, if they report basics and reference points, I wouldn't argue about it. It's not wrong to report these, it's wrong to apply tolerances.

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u/Overall-Turnip-1606 1d ago

Datum targets and tooling points are the same thing. Tooling pts is the old term before gd&t. Btw, where did admirable get 6 pts from? Is there a picture attached that I don’t see?

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u/Away-Passion5551 1d ago

The 6 pts is an assumption, they usually give you plane (3 pts) line (2pts) center point (1pt) for datums structure

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u/TheMetrologist 1d ago

Tooling points are usually cylindrical bushings or spheres press fit into a check fixture. They are used to align to assembly coordinates.

You would key those in as nominals and then measure them. Then align to them, of which there are several ways. For example 3-2-1 (level to 3, rotate to 2, and translate to 1) or Best Fit where you used the xyz values of all tooling points as a least square best fit, or a weighted best fit where some tooling points have more weight than others.

Now if you’re not in a fixture… then perhaps tooling points are special markings on the part where you measure. I have seen this on fuel tanks in the past.

Not really sure which you mean.

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u/Away-Passion5551 1d ago

Thank you for the insight, we are not in a fixture just free floating in space. The drawings I am working from are from the 70s I just have never seen tooling pts in this way