Calibration of Tape Measures used for reference



We are doing our quarterly audit and one of the auditors has raised the question about how do we calibrate & control tape measures - the operator control plan states to maesure a coil width Characteristic (for reference only) - device to use ( tape measure). Does this device need to be calibrated or can we just give it a number record the information in our gage control system as for reference only? How do other company's meet this requirement in their system??

Jerry Eldred

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I'm not exactly certain how to interpret some of your question. I'll try to answer based on what I think you mean.

If the accuracy of the parameter measured with the tape measure matters and is in your control plan, the tape measure needs to be calibrated. Calibrating them is a pain, and there are a number of avenues I've seen used. One method is to purchase tape measures with certificates of calibration from one of the metrology quality manufacturers (people that make dimensional tools such as Mitutoyo, Webber, Starrett, etc.). Another option is to have them periodically calibrated (I've seen that done quite often as well, and there are some pretty copst effective methods to do it such as purchasing a metrology quality ruler which is periodically recalibrated).

The other option would be if "for reference only" applies. I'd have to look at the specifics to understand. It seems ambiguous that the control plan says to make the measurement, then says it is for reference only. That is the part that confused me. If the measurement is truly for reference only, and is not a critical spec on your product, I don't quite understand it being in the control plan.

I am admittedly not a QS9000 expert. But it seems in my recollection that the common practice is to put the critical specs in the control plan. Those measurements and controls that are not critical are not normally listed. Maybe one of the QS9000 experts can un-confuse me on that point. If I am correct on this, that may be the source of confusion.

I'm not sure how much help I've been. Any of you QS9000 experts feel free to jump in.


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For what it is worth, at my last division - QS cert - we purchased all of our tapes from one manufacturer. We did a tape verification at the beginning of each shift and recorded that it was done on the production report. Our verification was that there were no obvious defects (the tape was whole, not broken), the end was securely attached and the numbers and lines clearly visible. I had an auditor (surveillance audit) tell me that this was not good enough. I led him to our customer complaints and product nonconformances databases and told him that untill we found nonconforming product directly traceable to an out-of-calibration tape measure, we were satisfied and so were our customers.

One thing to keep in mind, this was basically raw material, length tolerances were never tighter than -0 +1/2". We never received a nonconformance, nor was there ever a complaint that was traceable to tape measures. They are still using that system.

You really can't calibrate a tape, there are no adjustments. If worse comes to worse, buy a long steel rule and lay out your tape for verification.

Jerry Eldred

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I've heard some rather lengthy debates about tape measures. I don't know what it is about them.

Depending what semantics philosophy used, the tapes can't be adjusted, but they can be performance tested to assure they are within tolerance, which includes length, legibility and proper functionality of the end tab.

I must note that back in my third party days we received tape measures from some customers that were out of tolerance. I am a strong proponent of an initial verification, or at least accompanying certificate of calibration from a reputable manufacturer. There are "home handyman" brands, and there are professional brands. The easy selection is to save purchase money with a home handyman brand, then get an initial certification, or buy the good brand with an accompanying cert.

I will go on record that I have seen tape measures that do not meet their published specifications. I believe it was ISO10012 stated (if my memory serves correctly) "..the manufacturer's CLAIMED specifications..." (not actual quote, from my best memory).

Manufacturer's don't always make every product to spec. A good tape measure that initially meets specs will likely remain in spec until it is worn out.

A bottom line here is that the actual accuracy needs to be adequate for the intended use. If your product tolerance is +/- 1 inch, and the tape measure tolerance is +/-1/16th inch, you'll very likely never have difficulty. If, however your product tolerance is +/-1/8th inch with the same tape measure, consider a little more carefully how you maintain your tape measures. It's all about making sure the product you sell to your customer is what you claim it to be. Whether that means buying tape measures off the shelf with no maintenance other than throwing them away, or periodic verification against a standard ruler depends on %R&R, ratio between tape measure specs and your product tolerance. Let common sense and honesty "rule" (pun intended).


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the way we did it

We use tapes to verify the size of our sheet blanks. Dimensions are not critical, +/- .5". We addressed it by stating that tapes were for reference only and not used for product acceptance.



Fully vaccinated are you?
> I had an auditor (surveillance audit) tell me that this
> was not good enough. I led him to our customer complaints
> and product nonconformances databases and told him that
> untill we found nonconforming product directly traceable
> to an out-of-calibration tape measure, we were satisfied
> and so were our customers.

This can be key in many areas when auditors are looking for things like 'effectiveness' and such. I've used it a lot. Good response.


Involved In Discussions
It seems to me that the problem could be clarified by answering two basic questions.
1. If the measurement does not really matter, why are you measuring (and recording) it?
2. If the measurement does matter, why would you not want to verify it through calibration?


Tape Measure MSA

First time here, if I am typing in the wrong place etc. please let me know. This whole subject of tape measures came up in our recent QS9000 audit. We are a second tier automotive supplier of steel sheet and plate. We do in fact use a tape measure to verify conformance to customer's requirements in lengths greater than 80". How then is 4.11.4 (MSA performed on all test equipment referenced in the control plan) satisfied with tape measures?


A little more information that is causing this problem I guess it's not just the calibrated tape measure but it's how the characteristic is identified on the "Control Plan " as well. I'm looking for something solid I can tell my Audit Team for clarification.

Our Steel Coil Control Plans have a characteristic I.D of coil identified in the sequence of measurements the characteristic is just a quick check to make sure the operator doesn't grab the wrong coil and try to put it up on the coil reel which will not accept the coil if it is not the correct size. My question is can the term "For Reference Only" be used on the control plan, is there anything in the QS9000 standard or the APQP Manual that states this term may not be on the control plan???? I'm having real diffuculty with my Auditor about this I believe subjective interpratation.
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