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This thread is carried over and continued in the Current Elsmar Cove Forums 
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This thread is carried over and continued in the Current Elsmar Cove Forums
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The New Elsmar Cove Forums
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 The New Elsmar Cove Forums
 Measurement, Test and Calibration
 Steel Tape Rules
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| Author | Topic: Steel Tape Rules |
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Stu unregistered |
posted 21 November 2000 12:38 PM
 
We are being audited very soon. Today I was informed that I had to have a calibrated steel rule for my division and that anyone who had a steel rule in their tool box had to have a reference only sticker put on it. We are a repair shop and the CAR that resulted in this new rule stated: "The special instructions on a repair asked for three foot testleads. The technician used his own tape measure to cut the wire for these leads. This tape was not calibrated." Is it that critical?! IP: Logged |
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Graeme Forum Contributor Posts: 30 |
posted 21 November 2000 01:36 PM
 
An important question is "does the length of the leads have a significant impact on the quality of the measurement?" The answer is probably "No" unless you are working with UHF or microwave radio frequencies, or with very high current or very low resistance. The length requirement most likely comes from the fact that it is a common stock length, is convenient to work with, and is probably what the original engineer happened to have on hand. If the length truly is not critical, is it possible to change the implied exact measurement requirement to something with more flexibility? Then you can get back to the work of generating income by repairing widgets. If the length truly IS critical, there should be a tolerance listed, and in that case the cable needs to be measured and marked with the length. If this is the case then you MAY need a calibrated rule if it is your usual practice to make these cables as needed. And you have to have a procedure for making cables. (and lots more ...) Or if you normally purchase cables, then you have to start inspecting them for that parameter. (As you can see, a small question can generate a lot more "stuff".) So first, ask how important the "three foot" value is, and document the answer. (Another question is "does this requirement come from a bureaucratic organization that requires 100% verbatim compliance?" In that case, the easiest solution often is to quietly surrender and do what they say.)
[This message has been edited by Graeme (edited 21 November 2000).] IP: Logged |
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Alf Gulford Forum Contributor Posts: 60 |
posted 21 November 2000 06:04 PM
As they're used here, steel rules, tape measures and yardsticks don't need to be calibrated and that's what we say in our M&TE procedure. We do say that before use the assember must visually check for damage (e.g.; tape measure end bent in or out). This has been acceptable to two registrars. Alf IP: Logged |
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CJacobsen Forum Contributor Posts: 48 |
posted 21 November 2000 08:17 PM
If you have already specified a method for checking the tapes before use (the visual you described) then to make sure that it is clear the status of the tapes, I would add a "working Equipment" or "Reference Only" or "Not in Calibration System" or even a "Verify Before Use" label on each tape/device. ------------------ [This message has been edited by CJacobsen (edited 21 November 2000).] IP: Logged |
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Steven Truchon Forum Contributor Posts: 89 |
posted 22 November 2000 06:19 AM
For what its worth, in my life I have owned a steel rule and a tape measure that were both at about 7/8 scale. One inch on the steel rule measured .875 Over 3 feet, that would yield a 4.5 inch error! Prior to that I scoffed at anyone requiring "calibration" of such tools. But I quickly found that a simple documented verification was worth the little time it took to have it done. IP: Logged |
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Leo unregistered |
posted 22 November 2000 11:15 AM
In our facility we use many steel tapes and rulers to verify cutting lengths of cable and small diameter tubing. We have determined that the length of these cuts are important to the quality of the finished product and tolerances have been assigned. As we receive any steel tapes and rulers, we verify their measurements against our standard. About 5% of them have been rejected, usually because of a faulty starting edge. Those that pass the initial verification are then checked on a regular basis for damage that would affect accuracy or readability. This is a documented procedure that has stood through all of our audits. IP: Logged |
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energy Forum Contributor Posts: 228 |
posted 30 November 2000 09:02 AM
I recently talked to a person who is an "Inspector" for a well know measuring tape manufacturer. I laughed and asked what do you inspect? He commenced to relate some horror stories of contractors using defective tape measures that were 1" short in 25 ft. There was actually 1" missing on the metal roll. The fact that an individual can make a living inspecting measuring tapes tells you that they are not perfect. IP: Logged |
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David Drue Stauffer Forum Contributor Posts: 25 |
posted 08 December 2000 11:38 AM
Hi guys, I would like to throw in my two cents. Calibration of measuring instruments is required on any items used for the purpose of product acceptance. If a gage is used to measure characteristics that appear on a drawing that has specification limits associated with it, that gage or gage system (surface plate, height gage, & test indicator in combination) is subject to regular calibration. End result is that your product acceptance is based upon the measurement results produced by that measurement system. Also, good metrology practice states that anytime you are relying upon a tape measure or scales, measurements should me acquired by starting at the 1" line and taking the measurement from there rather that relying upon the measurement from the end which is highly susceptible to damage causing measurement error. Also, any linear measurement device should be verified for accuracy against a standard of known values before it is put into service. This may be as simple as the comparison to two other linear measuring devices that are in agreement with one another if a standard is not available. IP: Logged |
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energy Forum Contributor Posts: 228 |
posted 08 December 2000 02:45 PM
I like that. Like two out of three? Why not? IP: Logged |
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Boater unregistered |
posted 14 February 2001 03:33 PM
Hi folks,I`ve been charged with the calibration duties at our ISO 9001 certified yacht building facility. Our registrar suggested at our last surveillence audit that we need to calibrate all of our tape measures in-house. Tape measures are used in all areas of our business, we`ve got a pile of them. Do any of your companies supply tape measures? How do you police the many tapes out there on the manufacturing floor? Also, must a certified master be used or can we simply designate a new steel yardstick as our master and go from there? IP: Logged |
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Al Dyer Forum Wizard Posts: 622 |
posted 14 February 2001 04:32 PM
Boater, Just a suggestion: Buy a certified standard (s) for the length of measurements you are taking. Set up a schedule where the tape measures are verified against the certified standard (s). Determine how often the standard (s) has to be calibrated by an outside souce (re. cal lab). Follow the verification requirement you set down in your procedure. MHO ASD... IP: Logged |
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Ryan Wilde Forum Contributor Posts: 20 |
posted 16 February 2001 07:44 PM
The easiest method I've seen in use is to order the tape measure calibrated (I won't mention any company names, but the better manufacturers will provide calibration). After that, calibrate the tape measure yourself. Much like any static length measure, all wear will happen at the end, and the middle will be unaffected. Therefore, after you have the entire length of the tape calibrated ONCE, checking a single point referenced to the hook of the tape measure is the appropriate method. A steel rule works nicely, as does a gage block. You will find that the only thing that ever goes wrong in the accuracy of the tape is that the rivets begin to get sloppy, and the tape is ready to be replaced. ------------------ IP: Logged |
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Quality Guy Lurker (<10 Posts) Posts: 1 |
posted 06 March 2001 04:39 PM
I read all of the replies to this thread, but the focus seems to be on short (<16') lengths. The product I am working with can be up to 40 feet in length. The tolerance is ±0.2" (± 5mm). Does anyone have a any thoughts on a procedure for tapes of this length (up to 66')? Your assistance is much appreciated. IP: Logged |
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Jerry Eldred Forum Wizard Posts: 136 |
posted 06 March 2001 05:11 PM
I don't believe much would change in verifying a longer tape measure. The method would still be similar. One method I have seen is use of an adequately accurate certified steel ruler. Perhaps a meter or more in length. Or even a twelve foot or longer ruler, mounted on an adequately flat surface. We have one flush mounted on a counter surface we use for measuring thermocouples. The ruler could have quite a bit longer calibration cycle, as it doesn't stretch and wear in the same way a tape measure does. The ruler would be used to calibrate the tape measure in increments of twelve feet at a time (or whatever length ruler is used). ------------------ IP: Logged |
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Paul Williams Lurker (<10 Posts) Posts: 1 |
posted 10 March 2001 06:17 PM
Just a few thoughts from a calibration laboratory: 1. For longer measurements, the amount of tension on the tape becomes critical. 2. When calibrating a tape, we check end play on the hook to determine that it is functioning properly. Tape hooks are designed to move the thickness of the hook so that the hook is at zero in tension and when butted up on an object. Too much or not enough end play can fail the tape. 3. Standard tolerances for calibrating tapes can be surprising. For instance, the maintenance and acceptance tolerance for a 25 ft. tape is plus or minus 1/16". For most measurements that's not a problem, but you need to consider that required accuracy of the measurements that the tape is to be used on. You may need to specify a tighter tolerance than the standard when you have your tape calibrated to meet your customer specifications. 4. NIST Handbook 44, Section 5.52 specifies tolerances for length measurement instruments. It is available for download at the NIST website - go to the Weights and Measures area. If anybody has any questions, feel free to contact me at [email protected] I'll be glad to help if I can. IP: Logged |
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energy Forum Contributor Posts: 228 |
posted 12 March 2001 01:05 PM
As we are moving forward towards ISO 9001:2000 registration, a review of our measuring equipment indicates that 90% of our measurements are performed with 25 or 30 Foot steel tapes. Manufacturing tolerances vary from 1/8" to 1/4" for steel structures. For our piping assemblies we allow a +/-1& 1/2". Inspector's dream. My feeling is that we show who has them, periodically check the hook, record it and move on. Why heck, we might even serialize them. Is there an auditor who may have a problem with this? Count on it! But, I think when they are shown what we do, they too, will have to move on. After all, "we will do what we say we do." IP: Logged |
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