Calibration Frequency for Rarely Used Gages

[Bob_M]

Do you calibrate as recommended when gage has only been used 1 or 2 times?

If you have a gage that you use seldom to rarely (1-6 times) during a calibration cycle (which is typically one year), do you still get it calibrated? It seems like a large waste of time and money to calibrate/verify a piece of equipment that is hardly used.

EXAMPLE: We use 2 dial indicators in the production area (tooling department and machine maintainance) and 1 that we use in the "lab" with our height indicators. I sent them out annually as needed. We have 6-8 dial indicators total. We only use the other 3-5 indicator as substitutes while the normal ones are sent out for calibration. Does 1 week's worth of use justify calibrating these "extra" gages every year?
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I have seen plenty of good ideas/programs posted here like placing a rarely used gage in a sealed bag after calibration. If unopened, the following calibration just involves a new sticker. How does this work if you can't physically seal it?
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Other people simply mark "do not use until calibarted". This really only works if you can calibrate it in-house and/or don't need it in a rush. I've done this on a few attribute and go-nogo gages which are currently not needed (semi-obsolete product line).
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Any tips/comments on whether or not I should calibrate rarely/never used gages or simple extending the calibration cycle time.

(I've only been Quality Manager for 1 year and I'm about to send out gages again that have not been used or rarely used in one year).

Thanks Bob M

 

[Craig H.]

Bob:

To me this is a judgement call, depending on expected usage. If you have a gage that has not been used and you do not anticipating needing it, I would mark it "do not use until calibrated".

For gages that see little use, but when needed are needed immediately and cannot be calibrated in house, they should be sent out to be calibrated, IMO. The reason is that over a year, a measuring device can be jostled, and it would be subject to dust, humidity and heat/cool cycles.

You might check with the manufacturer to see what they say about calibration.

Hope this helps.

Craig

 

[Jimmy Olson]

One option you can consider is extending the calibration cycle on the gages that aren't being used often, as long as they are staying within specs each time they are calibrated. Some people are comfortable with this and some aren't, but it is something to consider.

 

[Bob_M]

Bob:

To me this is a judgement call, etc.

I also assumed that those that can not be calibrated in house should TYPICALLY be sent out as scheduled.

The seldom used gages are already stored in a cabinet in our semi-climate controlled quality lab (same heat/air system as the office). So jostling and major temperature changes are not a major problem.

Most of our seldom equipment includes - Height Gage, Height Master, dial and test indicators, extra micrometers, old or obsolete go-nogo, old or obsolete part specific gages, even our surface plate is hardly used except for gage calibration and occasional part verfication.

I'm not talking about saving the company alot of money, but I'm just looking for options/ideas. On the surface it seems crazy to annually pay to verify a gage you have used 2-3 times, just because you have a "calibration program".

I probably will send most of the stuff out, but I'm just looking for other people opinions and how they work with this situation.

 

[Bob_M]

One option you can consider is extending the calibration cycle on the gages that aren't being used often, as long as they are staying within specs each time they are calibrated. Some people are comfortable with this and some aren't, but it is something to consider.

I am considering this on a few.
12 months vs. 18
1 year vs. 2 years

Is it OK for US to set our own frequency on seldom used equipment?

 

[Jimmy Olson]

Is it OK for US to set our own frequency on seldom used equipment?

Yes it is. Check the history on the gages to make sure that they have been within the specs and then you can push them out. Make sure to track them and make sure they stay within during the longer period though.

 

[CarolX]

Bob,

I just went through this myself. The "status quo" around here was to calibrate our dial calipers on a monthly basis. I just changed it to quarterly based on historical review. We rarely found an out of tolerance condition at calibration. If there was a problem with the gage, the operator would find it long before it was due for calibration.

I have a set of angle blocks that are used once per year for checking our protractors. I set the calibration frequency for 5 years.

JMHO, as always.

CarolX

 

[Bob_M]

Bob,

I just went through this myself. The "status quo" around here was to calibrate our dial calipers on a monthly basis. I just changed it to quarterly based on historical review. We rarely found an out of tolerance condition at calibration. If there was a problem with the gage, the operator would find it long before it was due for calibration.

I have a set of angle blocks that are used once per year for checking our protractors. I set the calibration frequency for 5 years.

JMHO, as always.

CarolX

Monthly? Wow!

I like that idea for angle blocks and similar... I should check to see if anyone is using ours in the tooling department...

 

[Claes Gefvenberg]

Bob,

I just went through this myself. The "status quo" around here was to calibrate our dial calipers on a monthly basis. I just changed it to quarterly based on historical review.

Exactly,

The calibration period should reflect the calibration results... A while back we had to go in the opposite direction and put a number of micrometers on a monthly schedule due to increased use. The calibration results made it blindingly clear that the previous three month cycle was to long.

On the other hand, if the results stay well within the limits every time the period could (or rather should) be extended. To calibrate too often serves no useful purpouse, and not doing it often enough may of course be a lot worse.

Calibration prior to use is a good option when it comes to infrequently used equipment, because we are well adviced to consider that equipment can slip out of tolerances without being removed from its box... It's rare, but it happens.

Good thread here....

/Claes

 

[ljreimer]

Calibration Cycle

Based on some of the replays to your question about interval cycle for devices that are not use often, extenting cycle, and other options are valid. The main focus should be the application of use for the device.

A micrometer typical accuracy is ±0.001. If the application of use of the device being measured requires the values to of acceptance has a tolerance of ±0.005 you then have a 5:1 Ratio. The micrometer then could experiece a out of tolerance condition as high as 400% without causing a problem.

Look at the accuracy of the measuring standard, (your device) use to measure your product. find out what the ratio relationship is, then you can make informed decisions related to use, cycle and other conditions.