Calibrating or Verifying Metal or Steel Tape Measures

Sorry, I forgot about this thread.

Tape measures that we use measure in 1/16ths. That is the accuracy required for the products we make.
We just had a 5 foot vernier calibrated at an outside lab and we would like to use that to check the measuring tapes.

okay or not?

Crusader said:

Sorry, I forgot about this thread.

Tape measures that we use measure in 1/16ths. That is the accuracy required for the products we make.
We just had a 5 foot vernier calibrated at an outside lab and we would like to use that to check the measuring tapes.

okay or not?

Click to expand...

Not...
The measuring tape is there, just there. You use it and you are measuring and seeing the measure and recording it. There is no moving needle on a graduated dial or any digital display directly coming out from the measuring tape.
It is more better and cheaper to get duly certified measuring tape from factory and use them for some known frequency and discard to use a new one again.
The metal end of a tape measure slides back and forth slightly to ensure accurate measurements. Whether you hook it onto a board for an end measurement or push it against something for an inside measurement, the end will move to compensate for its own thickness. Most tape measures are divided into 1/32 inch increments for the first few inches to ensure accuracy.
It is mostly this part that fails your measurement on repeated and rough use. Look out for this damage and replace tape with new.

Underwriter's laboratories (UL) has a requirement that tape measures used in their tests be calibrated. The error that seems to concern folks is the tab on the end of the tape and any errors that it might introduce from either being poorly positioned or loose and moving around. An easy way to do it is to build a jig that lets you both push and pull against the tab to see if it has an effect on your measurement. As for the rest, compare it to gage blocks or any other decent length standard you might have.

Alrighty.....update on the "official" ruling in our recent registration audit is:

1. All measuring tapes must be verified against a steel rule. And the result documented periodically.
2. All measuring tapes must be uniquely identified.

I cannot challenge it. I tried already and lost.

The only thing that bothers me is that for the critical measurements, we do not use the end of the tape....we start at the 1" mark. That end tab never comes into play.


Just posting my recent experience. Just an FYI.

The only thing that bothers me, is why would you be using tape measures for critical measurements?

somashekar said:

Not...
The measuring tape is there, just there. You use it and you are measuring and seeing the measure and recording it. There is no moving needle on a graduated dial or any digital display directly coming out from the measuring tape.
It is more better and cheaper to get duly certified measuring tape from factory and use them for some known frequency and discard to use a new one again.
The metal end of a tape measure slides back and forth slightly to ensure accurate measurements. Whether you hook it onto a board for an end measurement or push it against something for an inside measurement, the end will move to compensate for its own thickness. Most tape measures are divided into 1/32 inch increments for the first few inches to ensure accuracy.
It is mostly this part that fails your measurement on repeated and rough use. Look out for this damage and replace tape with new.

Click to expand...

Well, if you follow that logic, there would be no point in calibrating gauge blocks or steel pins. They are just a block of metal. But yet we all agree, they should be verified periodically. Why are we making this so difficult? Verify the gauges are providing the correct readings. Then, move on.

Helmut Jilling said:

The only thing that bothers me, is why would you be using tape measures for critical measurements?

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Resources and the nature of the product do not warrant anything more - we have a unique product.

If you are using the tape measure to accept product then it is not considered "For Reference". Unfortunately we have all of ours calibrated but they are on a 3 year cycle.

ddouglas said:

If you are using the tape measure to accept product then it is not considered "For Reference". Unfortunately we have all of ours calibrated but they are on a 3 year cycle.

Click to expand...

3 year cycle? How often do you verify them against a calibrated gauge?

I know this topic has been beaten to death but I do not agree with my boss on this. First I will give you a little background on what I do. I work for a API licensed facility. Our main source of work is catering to the Oil & Gas industry. We basically only thread new and used casing. That is the majority of the work we have. I am the shop foreman of the facility. I have setup our calibration procedures and trained our Quality manager in all aspects of his job. I wrote our procedure for calibrating tapes and rules as a visual verification process for simplicity. I purchased a "certified Starrett tape measure for verification of our tapes on the shop floor. It is only used for verification purposes and is not used at any other times. We break or wear out a tape faster than the calibration cycles that they are on (1 year cycle). Knowing that the products we make generally have a loose tolerance and the lengths are not that critical that is why I wrote it as such. API 5CT is "our bible" in there it clearly states that we must be able to measure within +/- .1' (yes one tenth of a foot). So obviously there is not a real need to have anything more accurate than a simple tape measure. With that said my boss wants me to reference standards specifically for calibration purposes of these tools. I have purchased ASME B89.1.7 which is fine for tape measures. I have not been able to find anything on Steel Rules. I did noticed in this thread that a JIS standard was referenced. Assuming that standard is written for metric units and not USI I would like to know if there is any standard that is available for us "behind the time folks"? If someone could point me in that direction I would appreciate it.