Bringing Simple Calibrations Back In-House

[carolk79]

Hello,

I have been working in ISO for only about 2 years now and I need a little help. This is really kind of simple but I want to make sure I do it right. Here's the situation. We have been ISO certified for about 4 years. We have always done our calibation out of house and I would like to bring it in house.
This may be very difficult in some factories but in we only calibrate tape measures and rulers.

Now can we just use say a 5 foot hard metal ruler and get that calibrated out of house and traceible to NIST and then calibrate the tape measures off of that ruler????

That was my thought but I don't know anyone who does it so I really don't know if it is legal through ISO.

Please help me with this.

Thanks Carol

 

[cochranemurray]

Simple calibration

Hello.
We bought a calibrated steel rule which was already certificated. It was designated "Master" and is not used for day to day measuring. All other tapes and rules are checked using this one and a "calibrated" sticker attached. We also have an inventory of calibrated tapes. Our procedure states that calibration check will be carried out on receipt of new tapes. Thereafter, metal tapes should not need rechecked if they are kept in reasonable working conditions as they will not shrink or expand. It is encumbent on the equipment holder to ensure that it has a calibration sticker, it is not damaged and the scales are readable before use. This check is signed for on our batch paperwork. No complaints from auditors so far.
Regards

 

[Hershal]

Interms of the TAR (Test Accuracy Ratio), yes the metal ruler is more accurate.....

But the first question is, why calibrate a ruler or measuring tape?

 

[carolk79]

I don't know!!!!! When I started doing ISO for the company they were already calibrating tape measure and rulers so I just figured that it had to be done. I always thought it was strange but never questioned it. I guess I just assumed that they had to be because they have been doing it for so long.

Do they have to be?????
What will they auditor say if they are not???

 

[Dave R - 2005]

The calibration method sounds fine, I've been doing something similar for nearly 10 years and its been OK for two versions of ISO 9001, QS9000 and ISO/TS 16949. As for do you need to
calibrate, ask this question, do you make product-quality decisions based on what the gauge/instrument is saying? If your
answer is Yes, then you need to know the status of the gauge/instrument you are using, so get calibrating.

 

[QChas]

10 years with tape measures and they must be calibrated if used for accepting product. The clip on the end becomes loose from letting them snap back in place.

 

[Hershal]

My personal opinion.....nothing more.....calibrating tape measures and most rulers is a silly waste of money.....BUT

Some of the high end metal ones could reasonably be expected to be cal'd, but realize that even they are unreliable below 1/32 inch.....measuring tapes are unreliable below 1/16 inch.....that is, they may indicate some value, but how believeable that value is.....

In reality, if you need a tight measurement, you will use something else to measure if at all possible.

Sometimes, the length dictates use of a rule or tape, and then you are stuck.....unless you expand the tolerance to 1/4 inch or better.....then the rule or tape is adequate.

Just my opinion.

Hershal

 

[Hershal]

Oh, one other point.....if the cal of the rule and tape will happen regardless.....don't forget to have the accredited calibration including measurement uncertainty, so when a measurment is performed with the rule or tape, you know that the true value is x +/- MU.....and the MU of the actual reading will be larger than the MU coming from the cal lab.

For example, a cal lab might report its MU as 0.1 inch, but the user would actually have a MU likely around 0.25 inch, so the measurement performed with the tape would be x (value) +/- 0.25 inch over some length (say, 18 inches).....and a different MU value beyond that length.

So unless the tolerance is wide, or length requirements leave almost no other choice, I would say not to cal therule or tape.

Just my opinion.

Hershal

 

[Jim Howe]

calibrating measuring tapes

My personal opinion.....nothing more.....calibrating tape measures and most rulers is a silly waste of money.....BUT

Some of the high end metal ones could reasonably be expected to be cal'd, but realize that even they are unreliable below 1/32 inch.....measuring tapes are unreliable below 1/16 inch.....that is, they may indicate some value, but how believeable that value is.....

In reality, if you need a tight measurement, you will use something else to measure if at all possible.

Sometimes, the length dictates use of a rule or tape, and then you are stuck.....unless you expand the tolerance to 1/4 inch or better.....then the rule or tape is adequate.

Just my opinion.

Hershal

I agree with Hershal! That having been said I do recall going through similar calibrations when performing wire harness work on the Abrahms tanks for General Dynamics! We used procedures just like the ones posted here already. It was a Mil-I environment and I could never talk them out of it. Some of the wire harnesses were 40 to 50 feet long and most were built on a certified wire board. Didn't matter to the GD auditors;i.e. calibrate the tape !!!

 

[vanputten]

Hello Carol:

When you say you have been working in ISO for 2 years, what do you mean by "ISO?" ISO 9001:2000? ISO 17025:1999? ISO/TS 16949:2002?

If you mean ISO 9001:2000, you might want to think about your use of the term "calibration." You may really be verifying your measuring equipment as required by 7.6 Control of monitoring and measuring equipment. The connotation with the use of the term "calibration" is peculiar in relationship to tape measures. But if you think of it as verifying your measuring equipment, the intent of the requirement may make more sense.

Regards, Dirk