Calibrating or Verifying Metal or Steel Tape Measures

A relate question: For measurement traceability the std says "calibrated or verified at specific intervals to international or national measurement standard." Can a common sense approach using verified standards be used to verify tape measures, scales, calipers etc. Paying an out side firm $30 to have a 12 dollar tape measure is not cost effective. Can someone with a long history working in Quality using a well written procedure stating method, frequency and maintaining in-house verification records satisfy section 7.1.5.2? I have an external auditor telling me all equipment must be calibrated to NIST at an accredited lab... Thoughts?

Tab

Keep some calibrated "standards" like blocks, plates, rods, rules whatever and verify your tapes against them.

There isn't any requirement for everything to go to a laboratory.

Tabashwill said:

A relate question: [FONT=&quot]For measurement traceability the std says "calibrated or verified at specific intervals to international or national measurement standard." Can a common sense approach using verified standards be used to verify tape measures, scales, calipers etc. Paying an out side firm $30 to have a 12 dollar tape measure is not cost effective. Can someone with a long history working in Quality using a well written procedure stating method, frequency and maintaining in-house verification records satisfy section 7.1.5.2? I have an external auditor telling me all equipment must be calibrated to NIST at an accredited lab... Thoughts?

Tab

Click to expand...

A common method is to buy a good steel rule (3', 4', 6') at Lowes or Home Depot, or from a catalog, have it calibrated, and glue it down to a sturdy table. Then, since the rule is traceable to NIST, you can verify all your tape measures frequently to this one steel rule. There is nothing in the standard that says everything has to be calibrated by an outside lab...

The steel rule is an excellent choice to verify. We are ISO 9001 and we purchase a certified tape measure every year rather than calibrate. We don't verify its use due to minimal use and tolerances of our product.

Tabashwill,

I assume you are being audited to AS9100D.

You do need to have traceability to NIST or another national body. If you calibrate these yourself it will be up to you to show the unbroken chain of calibrations back to NIST.

There is no requirement for you to use an accredited lab to satisfy AS9100. Other standards can require the use of accredited labs. UL pushes hard for you to use accredited labs, even for tape measures.

If you are looking for a procedure to calibrate these, ASME B89.1.7 is available, but it may be overkill based on your requirements. Yes, you can write your own procedure.

Hi Trainee, when calibrating your tape measure it is important to ensure the metal hook on the end is not damaged and securely held by the two rivets.

If this is not the case and the metal hook moves you can experience anywhere upto 2-3mm of incorrect measurement.

Referring back to Grizz1345 comment you want to;

1 Examine the tape for any external damages or other obvious signs of abuse or wear that may affect the accuracy or function.
2 Clean all surfaces to remove oil and/or any foreign material.

But, more importantly use multiple tape measures and compare readings. If they are the same then that should be a very accurate measure regarding the accuracy of the tape measure can bring - ± 1/32” (.031”).

If you want more accuracy then you can try other options such as metrology gear like micrometers and calipers will provide you a really accurate reading. You want to reduce as much error as possible so its important to know how.
Hope this helps.

Richard Wilde said:

Hi Trainee, when calibrating your tape measure it is important to ensure the metal hook on the end is not damaged and securely held by the two rivets.

If this is not the case and the metal hook moves you can experience anywhere upto 2-3mm of incorrect measurement.

Referring back to Grizz1345 comment you want to;

1 Examine the tape for any external damages or other obvious signs of abuse or wear that may affect the accuracy or function.
2 Clean all surfaces to remove oil and/or any foreign material.

But, more importantly use multiple tape measures and compare readings. If they are the same then that should be a very accurate measure regarding the accuracy of the tape measure can bring - ± 1/32” (.031”).

If you want more accuracy then you can try other options such as metrology gear like micrometers and calipers will provide you a really accurate reading. You want to reduce as much error as possible so its important to know how.
Hope this helps.

Click to expand...

I believe that .....
The metal hook is not securely held by the two rivets. It has a play of about 1 mm, which is to compensate for the thickness of the hook in internal / external length measurement...

I always found it cheaper and easier to buy new rather than calibrate tape measures

I have seen a process where the tape measures are calibrated using another tape measure. All tape measures were of the same brand and length. One tape measure was kept as a "master" and sent out annually to an accredited lab. All other tape measures would be compared to this tape measure. Is this an acceptable method to calibrate tape measures? The part that I found questionable is that the master tape measure listed its tolerance as +/- 1/32". The tape measures calibrated using this master tape measure were also stated to be at +/- 1/32"

The simple fact is that the tape measures nothing.
It is you who takes the measure, with your eyes and knowledge and experience and off-course using the tape....