Seeking Procedure(s) - Methodology: Calibration of Pin Gauges

[norly99]

Calibration of Pin Gauges

I'm the QAM at a company that makes plastic parts. We do not have the money to have an outside source conduct yearly calibrations on all our gauges. I have read about a few different methods mentioned in the forums such as calibrate before use, etc. Could someone explain this method a little more, and how it is documented. Or any other methods that they use to pass the Calibration section of ISO for pin gauges. Thanks in advance

 

[Marc]

This may help to start out with some general info related to pin gages:

https://elsmar.com/elsmarqualityforum/threads/5857/

I've seen micrometers used for calibration. As far as calibrate before use, the first question I have is how frequently do you use pin gages and what's their resolution?

 

[norly99]

Our pin gauges are used for final acceptance on alot of our product, so I know that they need to be calibrated. But what do you suggest for calibrating them, a calibrated super mic? I have decided to coat them with wax to help indicate which gauges have been used since the last calibration. I truely need help in the calibration process. We have had the set of gauges for several years and I don't believe we can get a certificate from the manufacture.

 

[Jerry Eldred]

Calibrate before use is intended for circumstances where an instrument or gauge is not used for some indefinite period of time. So to save calibration costs, it is placed in a controlled area where it cannot be used without authorization with the status CALIBRATE BEFORE USE, meaning simply that.

When it is determined that the unit is to be used, it is submitted for calibration at that time.

It sounds like CALIBRATE BEFORE USE may not, however, be the appropriate status you are looking for. Any gauge you use to determine product must have a known accuracy. Whether you send to an outside calibration supplier as the method for assuring that known accuracy is not critical. What is a must is to know that when you make a measurement of a product parameter, that it be correct.

Some questions to ask perhaps would be as to whether all of your gauges are used to measure product specified parameters. Another question is as to whether all of your gauges are used on a regular basis. Are some of them sitting in cabinets for indefinites periods of time? Have you researched what measurement instruments would be adequate to calibrate the pin gauges inhouse? Are the required specs being measured less demanding on some sets of gauges than others. There may be some variations on how some sets are calibrated (meaning it also needs to be well documented and labelled to preclude using the wrong sets on the wrong process).

Just a few thoughts. Any further questions let me know.

 

[norly99]

Some questions to ask perhaps would be as to whether all of your gauges are used to measure product specified parameters. Another question is as to whether all of your gauges are used on a regular basis. Are some of them sitting in cabinets for indefinites periods of time? Have you researched what measurement instruments would be adequate to calibrate the pin gauges inhouse? Are the required specs being measured less demanding on some sets of gauges than others. There may be some variations on how some sets are calibrated (meaning it also needs to be well documented and labelled to preclude using the wrong sets on the wrong process).

Just a few thoughts. Any further questions let me know.

Not all gauges are used for specified parameters, but some are. Some gauges are not used at all and do sit for long periods of time. We have alot of very common sizes like .250, .300 that are used on a daily basis. As for the instruments to calibrate with, we have not decided on this issue. We do have some parts that are critical and need gauges that are very accurate!

 

[Grizz1345]

The first question that comes to mind is what kind of tolerances are you checking with the pins? If it is .001 then you could probably get a .00005 OD mic to check your pins. The main problem is having a controlled environment (cal lab specs). What are the requirements you are trying to meet? QS 9000, ISO 17025, etc. This will have alot to do with what kind of equipment and environment you will need. Hope this helps.

 

[Al Rosen]

Why not calibrate the pin gages used daily more frequently than the ones used less often. Can you reliably keep track of the number of uses each one gets? If so, set up a calibration frequency based on use. Then, use the calibration data/history to adjust the frequency of calibration. If the some pins are wearing, reduce the cal interval. If there is little wear, increase the interval for those pins. Just a thought.

 

[Mike S.]

We usually use pin gages to do go/no go testing of parts with a tolerance of +/- .004" or more. We calibrated those gages to start every month, but time proved we could go to 3 months with no problem on most of them. We use micrometers to calibrate them and set the allowable tolerance based on the tolerance of the spec. we're testing -- i.e. we may require the pin be +/- .0002" from nominal if the tolerance is +/- .004" but we may allow +/- .0005" if the tolerance is +/- .010" etc.

The thing to remember is you cannot get a .3000" pin into a .3000" hole --or even a .3001" hole in most cases. We used ID micrometers with the pin gages to determine experimentally how much "clearance" was required to get a pin into a hole in our parts, then wrote some rules on what size pin was needed for a given size hole. For example, the "go" pin for a .3000" hole may need to be .2993" - .2995".

Hope this helps.

 

[Clockgauge]

Many pin gage sets in use are minus-toleranced (approx. .0002" under the marked nominal size for an inch set). These pins have gagemaker's tolerance like a no-go plug gage. Plus-toleranced pin sets (like go plug gages) are also available. If you have several sets, you should determine the tolerance direction and mark them so pins are uniquely identified for calibration traceability.

As for the critical ones requiring great accuracy, check out air gages from companies like Federal or Western. The accuracy is there, parts aren't damaged and the air spindle won't wear. One master ring gives easy setting, and you will have variable data for a better understanding of your process and it's output. It will come with a particle filter, but you will have to add an oil removal filter to the air supply line (compressor oil will get into the line). You don't have to buy it from the air gage manufacturer, filters suitable for instrumentation are sold by many industrial supply houses. Mine cost less than 50 dollars and I installed it myself.

Hope this helps.

 

[calibrationd]

pin gage calibration

If you are checking plastic parts with class ZZ pin gages you most likely can get away with calibration once a year. As a manufacturer you should follow the 10:1 rule which would mean that you would have to buy a machine like a supermicrometer with a resolution of .00001". I'm not sure what how much you can afford. Calibration can be relatively cheap. I have the capabilty to check pins as well as all other precision instruments. Let me know if you would like any more info.