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  Measurement, Test and Calibration
  Calibration of Tape Measures

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Author Topic:   Calibration of Tape Measures
dscumaci
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Posts: 4
From:Willowbrook, IL
Registered: Jun 99

posted 26 July 1999 10:39 AM     Click Here to See the Profile for dscumaci   Click Here to Email dscumaci     Edit/Delete Message   Reply w/Quote
We recently received a minor nonconformance during a surveillance audit. The finding concerned the calibration (or lack thereof) of tape measures used on our production floor. These tapes are used to confirm lengths after a cutting operation. I am looking for a logical, simple method for calibrating tape measures. Does anyone have any "best practices" to share? I appreciate the assistance.

Dom-

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ALM
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From:Philadelphia
Registered: Jun 1999

posted 27 July 1999 06:30 AM     Click Here to See the Profile for ALM   Click Here to Email ALM     Edit/Delete Message   Reply w/Quote
I think that you may need to provide more information on the subject.

Are the tapes used to "determine acceptance of the product" for movement to the next function area or for shipment?

If not, label them as "reference tools" (assuming that you have some other method of measuring/testing the product for conformance to specification.

If they are, I believe that you may be in a pinch. Tape measures are subject to so much regular abuse, malformation, and other circumstances that would impact their accuracy (to some tolerances) --> you might find yourself hard pressed to keep them calibrated (or spend a ton of time rechecking them).

Apologies for only being semi-helpful. Throw some more details out there so that those more knowledgeable than I on the subject can give you some better advice.

ALM

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QC4U
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From:Dyersburg, Tn., USA
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posted 27 July 1999 08:44 PM     Click Here to See the Profile for QC4U   Click Here to Email QC4U     Edit/Delete Message   Reply w/Quote
dscumaci: I must agree with ALM, more info is needed to give a helpful reply.
What type of verification is used at your facility to determine calibration of tape measures as specified under your calibration procedures?

------------------
GSH
Quality Mgr.
QS9000 Coordinator

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dscumaci
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From:Willowbrook, IL
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posted 10 August 1999 07:07 AM     Click Here to See the Profile for dscumaci   Click Here to Email dscumaci     Edit/Delete Message   Reply w/Quote
Gentlemen,
Thank you for your response and I apologize for the vagueness of the question. To clarify the matter, the tape measures are used to make accept/reject decision after steel bar has been cut. Tolerances for length of bar and plate range from 1/4" and 1/16". However, my question is what my be a logical means of calibrating the tape measures? Does anyone have experience implementing a process for calibrating tape measures? What are some options we may have?

Thank you for your help;

Dom

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Roger Eastin
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posted 10 August 1999 07:40 AM     Click Here to See the Profile for Roger Eastin   Click Here to Email Roger Eastin     Edit/Delete Message   Reply w/Quote
You can't calibrate a tape measure (because you can't adjust it to bring it back into conformance), but you can verify aspects of it. You can verify that it is still readable and you can compare it to a standard (if you suspect warpage, for instance). One option is to verify it at incoming inspection and then establish reasonable intervals for verification. Also, come up with rules of action, such as what to do if the tape measure has been dropped or been exposed to unusual wear conditions.

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Kevin Mader
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posted 10 August 1999 11:01 AM     Click Here to See the Profile for Kevin Mader   Click Here to Email Kevin Mader     Edit/Delete Message   Reply w/Quote
Remember to keep in mind that you are required to calibrate equipment through their usable range. Purchase the right Tape measure for the job. To add to Roger's post, consider the things that break or become loose (i.e. the end-hook on the tape measure). Is there any play?

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Batman
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From:Kane, PA 16735
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posted 10 August 1999 03:26 PM     Click Here to See the Profile for Batman   Click Here to Email Batman     Edit/Delete Message   Reply w/Quote
Do you need to consider the "readibility" factor, where the measurement device must read one more decimal than the stated tolerance? 1/16 is .0625. Your device should be readible to .006? (1/125?) This may be splitting hairs, but could this be an audit target, and more importantly an issuue for you? I guess it depends upon the criticality of the measurement.

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barb butrym
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posted 11 August 1999 04:04 PM     Click Here to See the Profile for barb butrym   Click Here to Email barb butrym     Edit/Delete Message   Reply w/Quote
keep a steel rule for verification when tape gets worn/abused ...discard (or tag) and replace with a new one when wear reaches an unacceptable level...the steel rule comes in calibrated/verified or what ever........and if not heavily used has an infinitye cal cycle....or tap on one of 15 years.....You set the rules, what makes sence for you

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Kevin Mader
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posted 12 August 1999 06:54 AM     Click Here to See the Profile for Kevin Mader   Click Here to Email Kevin Mader     Edit/Delete Message   Reply w/Quote
I agree with Barb's recommendation. Currently, our program to calibrate a tape measure includes verification that the end-hook does not have too much play (dependent on the nature of the tolerance and item being measured) by ensuring that when compared to a steel rule, the allowable slop is within your established limits. The rest of the tape should remain consistent, barring any kinks or bends.

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SRTipton
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From:Spencer, WV
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posted 17 August 1999 06:50 PM     Click Here to See the Profile for SRTipton   Click Here to Email SRTipton     Edit/Delete Message   Reply w/Quote
Regarding the tape measure, if I have a tolerance of +/- 1/8 inch, does that mean that I must be able to read the measurement to +/- 0.0125" if the measurement appears on my control plan but is not a customer designated key (special) characteristic? Also what about conversions from metric to English? As an example, say the spec for the thickness of material is 1+/- 0.1 mm; this would convert to (approx.) 0.03927+/-0.003927. How would this be handled best?

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MEParsons
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posted 18 August 1999 12:40 PM     Click Here to See the Profile for MEParsons   Click Here to Email MEParsons     Edit/Delete Message   Reply w/Quote
I have been involved in a debate around the "unique Identification" of tape measures used to accept and reject product. Most areas of our facility assign a number to "each piece" of IMTE and have a gage card matched to each piece as evidence of verification. Excellent work! One department has chosen to affix a verification sticker to each piece, but all IMTE verified in the same month all have the same sticker. No way to tell them apart and no gage card for each piece. All tapes appear identical. The only record is a list of operators and a check mark beside their name if they received a tape that particular month. I do not see a "unique identification" here. Am I missing something? Can tape measures be lumped into a category as one peice of equipment? HELP

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Marc Smith
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posted 19 August 1999 08:10 PM     Click Here to See the Profile for Marc Smith   Click Here to Email Marc Smith     Edit/Delete Message   Reply w/Quote
IMHO if each of the M&TE are NOT distinguishable in some way (serial number, colour, or equivalent), the 'unique' requirement is NOT being met.

[This message has been edited by Marc Smith (edited 19 August 1999).]

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Kevin Mader
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posted 20 August 1999 07:39 AM     Click Here to See the Profile for Kevin Mader   Click Here to Email Kevin Mader     Edit/Delete Message   Reply w/Quote
SR,

Converting English measure into metric often leads to errors. We are a 'metric' only organization and to avoid errors, we consistently measure and test in metric units. My suggestion: do not convert.

A majority of the time when we do have issues of conversion, they arise in the supplier arena. Often time, first piece inspections submitted are converted into English measure, and I can count on at least a few conversion errors.

Just a passing thought, so back to the group...

Regards,

Kevin

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Batman
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posted 30 August 1999 04:43 PM     Click Here to See the Profile for Batman   Click Here to Email Batman     Edit/Delete Message   Reply w/Quote
SRTipton-
Typically, if it is on the control plan, it is important, and being controlled.

From my limited experience, most methods of measurement dictate [roughly] adding another decimal to the readings. There are digital calipers, for instance, that read to 2 places. A part of 19 +/- .02 that measures 19.023 will read 19.02. The part is out of spec and you will accept it. At least the measurement device should distinguish .001 increments.

Without knowing your requirement, I suggest that if it is worth controlling, it is worth measuring correctly.

And I use .03937 to convert. See? As Kevin says, avoid converting.

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Marc Smith
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posted 30 August 1999 05:32 PM     Click Here to See the Profile for Marc Smith   Click Here to Email Marc Smith     Edit/Delete Message   Reply w/Quote
Yeah - the 'old' rule of 10!

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Jerry Eldred
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posted 03 December 1999 12:31 PM     Click Here to See the Profile for Jerry Eldred   Click Here to Email Jerry Eldred     Edit/Delete Message   Reply w/Quote
There is still the "calibration" versus "verification" issue. Regarding "verification" of tape measure (agreed- you can't calibrate as you can't adjust to nominal) must be done at least once. And must be redone periodically to check for play on the end clip and legibility of graticules/increementation.

However, one point did not seem to come up. If you have an initial certificate of traceability with uncertainty, etc from the manufacturer, that is one thing. But I have seen quite often on tape measures that one does not exist. So the accuracy of the tape measure must be measured. In my old days as a contractor metrologist, I have seen tape measures out-of-tolerance. They did not meet original manufacturers specs for length accuracy (we tested on a surface plate with either gage blocks or a metrology grade straight edge ruler, a variety of increment lengths and at various points along the length of the tape). There are some military verification procedures that specify this method.

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Sam
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Registered: Sep 1999

posted 03 December 1999 03:54 PM     Click Here to See the Profile for Sam   Click Here to Email Sam     Edit/Delete Message   Reply w/Quote
I have a cert from "Starrett" for a 12' tape purchased in 1997 that provides all the required info;
Guide 25 certified
dimensional verification
hook error
uncertainty
95%cl
plus specifications and procedures.
They are available, you just have to go to the right source.

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Marc Smith
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From:West Chester, OH, USA
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posted 30 March 2000 02:07 AM     Click Here to See the Profile for Marc Smith   Click Here to Email Marc Smith     Edit/Delete Message   Reply w/Quote
Akso see:
https://elsmar.com/ubb/Forum4/HTML/000097.html
and https://elsmar.com/ubb/Forum4/HTML/000130.html
and https://elsmar.com/ubb/Forum4/HTML/000170.html

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