Calibrating pin gages - Can we write a procedure "Calibrate before use"? Examples?
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"Calibrate Before Use" (CBU) in my experience is not a calibration method; it indicates the item must be calibrated before you use it. This could include items you send out to a vendor or what ever method applies.
The application of CBU would be if you are not going to use them for some period of time. You then could label them CBU, and calibrate them when you need to use them. This is a cost saver in terms of either manhours or vendor charges, but does not substitute for normal calibration.
As I am not a dimensional expert, I don't immediately recall the normal method (whether it be a high accuracy super-micrometer, or other dimensional measurement.
The application of CBU would be if you are not going to use them for some period of time. You then could label them CBU, and calibrate them when you need to use them. This is a cost saver in terms of either manhours or vendor charges, but does not substitute for normal calibration.
As I am not a dimensional expert, I don't immediately recall the normal method (whether it be a high accuracy super-micrometer, or other dimensional measurement.
CarolX
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I have my pin gages marked “Calibrate Before Use”. My procedure requires the pin be checked with a micrometer before use. This method works well for us. We have a large set and many of the pins are never used. At the other extreme, some are used daily and subject to wear. Not only does it save the cost of a yearly calibration of the set, it precludes the use of worn pins.
If it will work for you, go for it.
If it will work for you, go for it.
J
jager
Pins
And some are put back in the wrong hole in your gage pin drawer. It happens all the time. I like the idea of a sign saying to calibrate before using.
And some are put back in the wrong hole in your gage pin drawer. It happens all the time. I like the idea of a sign saying to calibrate before using.
You could have such a procedure and it would work well, depending on how the calibration is done.
You would need to send the pin(s) to a cal lab that includes pins and/or gage blocks in their scope. If they have been accredited by a recognized AB (e.g. IAS, A2LA, NVLAP, L-A-B), then the equipment, traceability, and technical proficiency of the personnel have all been assessed. That means they have a super-mic, controlled environment (20 C +/- 1 C), and are proficient at that specific measurement, and can provide the mesurement uncertainty so you know just what your actual measurements entail.
Yes, it is more expensive to use such a cal house and have the accredited cal.
Hope this helps.
Hershal
You would need to send the pin(s) to a cal lab that includes pins and/or gage blocks in their scope. If they have been accredited by a recognized AB (e.g. IAS, A2LA, NVLAP, L-A-B), then the equipment, traceability, and technical proficiency of the personnel have all been assessed. That means they have a super-mic, controlled environment (20 C +/- 1 C), and are proficient at that specific measurement, and can provide the mesurement uncertainty so you know just what your actual measurements entail.
Yes, it is more expensive to use such a cal house and have the accredited cal.
Hope this helps.
Hershal
T
Totumfrog
Our company literally has thousands of plug gages. We use the calibrate before use process. It has passed 3 years of audits. It's not even written procedure technically. It is simply a gage calibration / sign out sheet. The operator records who he/she is, what machine it is being used at (traceability), what the target dimension is (i.e. 1.0000"), what the actual dimension is (i.e. 1.0001"). We then have a column on the sign out sheet that specifies that the plug gage must be +/- 0.0002" of the target dimension in order to be used. If it is out of dimension, it is taken out of service. We use NIST traceable Mitutoyo micrometers that measure to 0.00005" for proper accuracy. The operators check the gage in three places (on both ends if it doesn't have a handle). This method has greatly reduced individuals from using the incorrect gage accidently. It also has helped us from shutting down a press when a gage may have a nick or ding on it that throws it out of tolerance. Lastly, it greatly reduced the QC time in having to calibrate every gage every 6 months or a year. The sign out sheet becomes your record of calibration. FYI...our gages are stored in a climate controlled environment so the ISO requirements for temp., humidity, cleanliness etc. are met as well. It should be said that our tolerances on our parts are no tighter than .003" total range. This procedure may not work properly if you have to hold .001" total tolerance.
G
gaugefixer
Write the procedure you want to do.
We are a machining shop with a small production environment and gauge pins are used all the time. I have "Mic Before Use" and "For Reference Only" labels on our gauge pin sets which seems to work fine.
As for yearly calibration; we do a visual check for missing and worn pins and replace them as necessary.
The pins are used on various jobs where bore sizes are anywhere from .061" to 1.000" and tolerances are generally .003". We do have bore gauges starting at around .360 and up so if someone has a tight tolerance of .0005" or less we give them a bore gauge.
It is not feasible to calibrate every pin every time it is used. I'd be babysitting pins and nothing else if I HAD to do that.
gaugefixer
We are a machining shop with a small production environment and gauge pins are used all the time. I have "Mic Before Use" and "For Reference Only" labels on our gauge pin sets which seems to work fine.
As for yearly calibration; we do a visual check for missing and worn pins and replace them as necessary.
The pins are used on various jobs where bore sizes are anywhere from .061" to 1.000" and tolerances are generally .003". We do have bore gauges starting at around .360 and up so if someone has a tight tolerance of .0005" or less we give them a bore gauge.
It is not feasible to calibrate every pin every time it is used. I'd be babysitting pins and nothing else if I HAD to do that.
gaugefixer
We have a few highly used pins that I put cal stickers on and calibrate on a fixed interval (i.e. every 60 days). Others, like entire sets, have an "uncalibrated - for reference only" or "calibrate with each use" sticker.
Calibration is done in-house with a written WI that specifies the use of .0001" accuracy calibrated mics and states how close the actual reading must be to the specified pin size for it to be used.
We also specify what the pin tolerance must be based on the hole size being tested and its spec. tolerance.
Calibration is done in-house with a written WI that specifies the use of .0001" accuracy calibrated mics and states how close the actual reading must be to the specified pin size for it to be used.
We also specify what the pin tolerance must be based on the hole size being tested and its spec. tolerance.
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