Calibrating or Verifying Metal or Steel Tape Measures

Crusader said:

100% of our final products are accepted/rejected using steel tape measures. We use the entire tape a lot of times to measure. Tape measures are various lengths but most are 25'. We're allowed up to +/- 1/2" tolerance when measuring the final product.

There are hundreds of measuring tapes all over the place that are not verified/calibrated, etc.. :mg:

My task is to verify all of them and put in a "calibration system". Can I simply buy a "master" tape and use that as its sole purpose for verifying all of the others out in use? Would that master need to go out to a certified lab to get "certified"??

Can it be that simple? The master steel tape measure does not have to be traceable to NIST, right?

:truce: Guidance please - much appreciated!!

oh yeah, there is no qc lab, no dept., etc. These steel tapes will be verified in the environment where used. I am the lab. I am the qc/qa dept. LOL!
and all of this must meet ISO 9001:2008 requirements.

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Crusader said:

<snip> Can I simply buy a "master" tape and use that as its sole purpose for verifying all of the others out in use? Would that master need to go out to a certified lab to get "certified"?? <snip>

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1. Determine how many tapes you actually need to perform the 100% inspection. These tapes would be clearly marked/distinguished from the others. I might put a large red sticker on the reference only tapes, or tape them up in a box in put them under lock and key.
2. If you have some new tapes, I would send them to a competent lab and have them verified. Set a 5 to 7 year recall.
3. If the tapes are getting worn and maybe don't roll up well, I would purchase new tapes. Check around to see if you can get some with certificates of calibration/verification. Then set the due dates.
4. Establish a very clear system which tape is to be used when; or just remove any tape not verified.

Jim Wynne said:

According to 7.6 of ISO 9001:2008, calibration or verification is required "When necessary to ensure valid results..." If you can demonstrate that calibration isn't necessary to ensure valid results, you shouldn't need to calibrate.

In practical terms, some level of control seems to be in order if there are tapes flying around all over the place. I think that if you identify them (some kind of unique ID number), create a register, and then periodically look at them (and keep a record) for damage, legibility, etc. You should be fine.

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BradM said:

There are a hundred ways to approach this. What I would do...

1. Determine how many tapes you actually need to perform the 100% inspection. These tapes would be clearly marked/distinguished from the others. I might put a large red sticker on the reference only tapes, or tape them up in a box in put them under lock and key.
2. If you have some new tapes, I would send them to a competent lab and have them verified. Set a 5 to 7 year recall.
3. If the tapes are getting worn and maybe don't roll up well, I would purchase new tapes. Check around to see if you can get some with certificates of calibration/verification. Then set the due dates.
4. Establish a very clear system which tape is to be used when; or just remove any tape not verified.

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Crusader said:

Yes, a control system is being established since there is not one at all. (I'm in a new company now)

All steel tape measures are required. In all stages. They are used incessantly to arrive at the final product, which is bought-off with a tape measure again.
I just want to get away with verifying these against a master tape measure (brand new) without having to send that master out to a "calibration" lab.

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Crusader said:

I've attached a pdf of a basic instruction for verifying tape measures. Will this pass?

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Crusader said:

I've attached a pdf of a basic instruction for verifying tape measures. Will this pass?

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BradM said:

The procedure is short, but to the point. It seems to cover things pretty well.

The only question I had is in regards to the visual inspection. 1/16" is the resolution of most rulers/ tape measures. I would think there is some attributed error based on different people with different eyesight and such.

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Jim Wynne said:

In all cases of making decisions like this, the important consideration is the tolerances of the things being measured. If the resolution of the device (whatever it is) is 1/16" and the tolerance of the thing to be measured is ?1/4" there shouldn't be an issue unless measurements are near the tolerance limits. Also, history has to be taken into account. If there is no history of measurement error contributing to nonconformities and it's been established that calibration is not "...necessary to ensure valid results," then calibration or anything beyond verification of basic function isn't necessary.

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BradM said:

Earlier the tolerance was stated to be ?1/4", but in the attached procedure, it states ?1/16" as the tolerance. 1/4" is not that big of a deal. 1/16" is getting pretty tight for a visual inspection.

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