Calibration Requirements for Thread and Ring Gages

[kerrdog1979]

If i dont include thread and ring gages in my master register of gages, do they need to be calibrated (i.e on a schedule, with updated calibration stickers and what not). It is not cost effective for our use of them to have them sent out yearly, so I would like to take them off the main register, but do not want to effect our AS9100 rev c status any advise would be extremely appreciated!! Thanks

 

[Darrell B]

Re: calibration of thread and ring gages

Plug gages are really not that expensive to calibrate, and I put them on a 2 year cycle. I have yet to have one come back reported out of tolerance.

 

[Michael_M]

If i dont include thread and ring gages in my master register of gages, do they need to be calibrated (i.e on a schedule, with updated calibration stickers and what not). It is not cost effective for our use of them to have them sent out yearly, so I would like to take them off the main register, but do not want to effect our AS9100 rev c status any advise would be extremely appreciated!! Thanks

I track our thread gauges and check them out to a machine and to a part number. If the gauge is not used in a 1 year period, I extend the calibration by 1 year. If after the 2 year period, I pull the gauge from active service and place it in a bond area.

If the gauge needs to be used after placed in bond, if my records show no use between calibration and placing in bond, I will issue the thread gauge for use then have it calibrated after it is finished.

I document all this and I believe this would pass any audit, mostly because I document it and it is what our procedures say to do.

For your reference, I will tell you what I pay for calibration of thread gauges:

$22.50 for each ring gauge 1" and lower
$32.50 for plug gauge (both sides) 1" and lower
$45.00 for each ring gauge and both sides of a plug gauge over 1"

The calibration (don't remember the exact classification) would be classed as short form.

 

[SmallBizDave]

The determination as to whether the gages need to be calibrated or not depends on whether they are used to verify customer product. If so, they must be calibrated in some way.

Extending the calibration period is a good way to reduce cost so long as you aren't going beyond manufacturers recommendations. Another way to reduce cost is to have one calibrated and then verify the others against that one. So long as your procedures say this is acceptable and you have appropriate records to maintain the traceability you should be fine.

 

[Jeff Frost]

You can set any calibration cycle you wish as long as it is based on valid reasoning. What standard are the gages made to (British Standards or US), what is the base metal of the thread, or are threads coated with an abrasive plating? All these factors could effect on the calibration cycle of the gages.

 

[MPetersen]

They definitely should be on your master list if you use them to verify product.

We ponied up and bought nice Mitutoyo 3-Wire sets to calibrate our most used thread plug gages. Expensive up front, but they are cheap to calibrate once a year and we check 100-200 thread plug gages a year with them.

Commonly used thread gages are every year whether we do them in house or not. Once in a blue moon thread gages are "calibrate before use" which means we send them out if we get a job that needs that gage.

We do complicated aerospace components so we have 3-4 drawers full of odd sized thread ring/thread plug gages that we don't calibrate regularly, just have it in the procedure that if you do need to use one of these odd gages to send it out first.

 

[dhibner]

We calibrate nearly 100% of our thread gages in-house. It can get very expensive to outsource all of your thread gage calibration if you have a lot of gages, and costs climb unnecessarily if you are calibrating occasional use gages every time you use them throughout the year. And if you have never had a thread-gage found out-of-spec by a calibration service, you either don't use the thread gages very often, the service is replacing gage members and not telling you, or the calibration certs are not being reviewed.

The drawback to annual calibration is you cannot possibly know when a thread gage is going to be out of spec., and if you do not know how to calibrate or check a thread gage for conformance that makes matters worse.

We use an automated tool vendor to issue and return gages. Considering the cost of an AS9100 or ISO13485 finding and possible re-certification cost (not to mention the associated stain), the crib costs less.

If you have the on-site resources for calibration, I would recommend purchasing a thread-wire set, super micrometer, and thread setting gages for ring gages to any company that has thread gages in use at anything greater than light frequency - Plug and ring gages are relatively simple to calibrate - about 10 minutes, and the assurance of knowing your gages are in spec. is priceless...why guess?

If you do not have a calibration technician on-site... track usage and have items calibrated per manufacturer specs or sooner.