Pros and cons to this measurement? Any references where I can more on COQ detailing out the prevention, appraisal, internal and external elements? Thanks!
Here's an article I wrote on the subject recently:
How to Calibrate Rulers Without Really Calibrating Them
by Christopher Paris
VP Operations, Oxebridge Quality Resources, Inc. www.oxebridge.com
Because retractable tape measures and rulers are sometimes used for measuring product, they fall under the calibration requirements of ISO 9001. However, formally calibrating them is often expensive and is not really necessary.
Instead, do the following:
1. Determine what brand of rulers or tape measures are in use. If there are lots of different brands in use, decide on up to three brands. Throw out all the other brands and replace with the three approved vendor brands. Reputable brands include Starrett, Lufkin, or Stanley. The less brands in use, the better.
2. Call the manufacturer of each brand (i.e., Starrett, Lufkin or Stanley) and request a Certificate of Manufacturing Tolerance. This is a statement or certificate from the manufacturer that says what the tolerance is that they build the rulers or tape measures to. This is usually about + / - 1/64". (Smaller is better.) Keep this certificate on file with your other calibration records.
3. If the tolerance given by the manufacturer exceeds (is tighter than) the measurements taken by your operators, then the entire brand of tape measure or ruler may be considered validated for use. So if your operators only measure to +/- 1/16" and the rulers are certified as manufactured to +/- 1/32", than they are approved for use.
4. Require that operators ONLY use rulers or tape measures from the accepted brands with whom you have certificates on file. Consider hanging signs that list “approved ruler and tape measure brands.â€
5. Because rulers and tape measures do not “go out of tolerance†under normal use, require that operators check their ruler or tape measure before each use for damage, loss of numbers, or edge wear. The metal tip on tape measures must be firmly affixed and not worn off. The starting edge of rulers must be sharp and completely free of wear.
6. Whenever a tape measure or ruler is no longer in good shape, replace it entirely.
With this method, there is no need to periodically calibrate tape measures or rulers. There is also no need to put calibration stickers on them because the brand name acts as the means to trace the device back to the manufacturer’s certificate on file. So long as it's an approved brand and in good shape, there is no need to have it formally calibrated.
This method has been used in multiple ISO 9001 certified companies and has been audited without problems by a number of accredited registrars.
(C) 2005 OQR, Inc. Posted to insidequality.com with permission.
With the changes from the 1994 to the 2000 ISO Standard, you may want to consider using verification in place of calibration. If this is a cost issue perhaps one piece may remain as calibrated and the remainder verified "prior to use". An auditor would still like to see some type of record as to the verification even though the ISO9001:2000 Standard does not specifically require such records.
A sample to consider: We have gage pins (200) for measuring hole sizes. These used to be calibrated but are now verified using calibrated micrometers of calipers.
The ability to use verification can save money but you must be careful if you have a written procedure stating that you will calibrate the measuring device. You may need to revise your procedure.
Hope this helps.
christopher_paris 6/17/2005
Here's an article I wrote on the subject recently:
How to Calibrate Rulers Without Really Calibrating Them
by Christopher Paris
VP Operations, Oxebridge Quality Resources, Inc.
www.oxebridge.com
Because retractable tape measures and rulers are sometimes used for measuring product, they fall under the calibration requirements of ISO 9001. However, formally calibrating them is often expensive and is not really necessary.
Instead, do the following:
1. Determine what brand of rulers or tape measures are in use. If there are lots of different brands in use, decide on up to three brands. Throw out all the other brands and replace with the three approved vendor brands. Reputable brands include Starrett, Lufkin, or Stanley. The less brands in use, the better.
2. Call the manufacturer of each brand (i.e., Starrett, Lufkin or Stanley) and request a Certificate of Manufacturing Tolerance. This is a statement or certificate from the manufacturer that says what the tolerance is that they build the rulers or tape measures to. This is usually about + / - 1/64". (Smaller is better.) Keep this certificate on file with your other calibration records.
3. If the tolerance given by the manufacturer exceeds (is tighter than) the measurements taken by your operators, then the entire brand of tape measure or ruler may be considered validated for use. So if your operators only measure to +/- 1/16" and the rulers are certified as manufactured to +/- 1/32", than they are approved for use.
4. Require that operators ONLY use rulers or tape measures from the accepted brands with whom you have certificates on file. Consider hanging signs that list “approved ruler and tape measure brands.â€
5. Because rulers and tape measures do not “go out of tolerance†under normal use, require that operators check their ruler or tape measure before each use for damage, loss of numbers, or edge wear. The metal tip on tape measures must be firmly affixed and not worn off. The starting edge of rulers must be sharp and completely free of wear.
6. Whenever a tape measure or ruler is no longer in good shape, replace it entirely.
With this method, there is no need to periodically calibrate tape measures or rulers. There is also no need to put calibration stickers on them because the brand name acts as the means to trace the device back to the manufacturer’s certificate on file. So long as it's an approved brand and in good shape, there is no need to have it formally calibrated.
This method has been used in multiple ISO 9001 certified companies and has been audited without problems by a number of accredited registrars.
(C) 2005 OQR, Inc. Posted to insidequality.com with permission.
smcuree 6/15/2005
With the changes from the 1994 to the 2000 ISO Standard, you may want to consider using verification in place of calibration. If this is a cost issue perhaps one piece may remain as calibrated and the remainder verified "prior to use". An auditor would still like to see some type of record as to the verification even though the ISO9001:2000 Standard does not specifically require such records.
A sample to consider: We have gage pins (200) for measuring hole sizes. These used to be calibrated but are now verified using calibrated micrometers of calipers.
The ability to use verification can save money but you must be careful if you have a written procedure stating that you will calibrate the measuring device. You may need to revise your procedure.
Hope this helps.
1/13/2006
yes, above two replies sound reasonable to handle these types measurement tools to reduce calibration cost.