Performing Internal Calibrations - Dial gauges, micrometers, height gauges, calipers


Starting to get Involved
Hi everyone,
I have recently moved into a new job where the compnay is certified to TS 16949. My previous job was in an FDA regulated company so there are a few differences between both that im trying to get my head around.
I have been asked to look after the calibration program within the company. The company has over 200 instruments which are mainly made up of Dial gauges, micrometers, height gauges and calipers. We spend a large amount of money getting an ISO 17025 accredited laboratory in to calibrate these instruments.
What I was hoping was that as we have the experience and personnel to perform these calibrations ourselves and we have our own measuring laboratory (not accredited to ISO 17025) is it possible do these calibrations ourselves with standards that are traceable to ISO 17025.
Is there certain laboratory conditions that need to be met if this can be done. I have procedures available and the personnel are trained on measurement, calibration and uncertainty of measurement and have years of expereince in measurement.
If it is possible to perform these calibrations internally without the lab been accredited to ISO 17025 will we still need to provide an uncertainty measurement?
Any help or information on what options or steps I need to take would be gratefully received. If this question has been answered elsewhere please point me in the right direction. Thanks,


Inactive Registered Visitor
Re: Performing Internal Calibrations - Dial gauges, micrometers, height gauges, calip

Hi, James!

If I understood correctly your instruments are already calibrated/certified by an outside accredited lab. Their certificates should carry the lab's uncertainty estimate.

The AIAG Measurement Systems Analysis manual 4th edition can provide some help and direction. Gregory Gruska, one of the team that wrote this edition and who ran the MSA roll-out training 8/12/10 said 'Calibration is a re-centering of the measurement device. If using stability as a re-calibration decision tool then re-calibration is not needed until such a time as the measurement process drifts out-of-control."

At risk of offending some, the XbarR chart or X-HI/Lo format lends themselves well to evidence ongoing stability.

Example: 0-1" micrometer.
Known areas of wear: Spindle thread, polished spindle anvils.
-The polished spindle anvils can be checked with a certified optical flat for wear periodically.

Choose 2 traceable standard gage blocks (say .1287" and .9782") to encompass most of the usable range.
-(1) chart, subgroup of 3 readings on the same block [0.1287"].
-(1) chart, subgroup of 3 readings on the same block [0.9782"].

Subsequent sub-groups can be used for other 0-1" micrometers. Any one that exhibits an out-of-control condition would then be sent out for re-calibration / refurbishment.

Time interval of charting could be based on usage with those used in continuous production checked very frequently (or even maintaining their own chart).

I have used this method myself (XbarR start of each shift) and it served to show not only stability but also evidenced operator skill at using the gages.

Best of luck!

P.S. The control chart limits for a micrometer that distinguishes to 0.000100" may only be 0.000200" wide. Consequently, the folks doing the inspection have to estimate to the nearest 0.000010". A digital micrometer will likely restrict this to 0.000050".
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George Weiss

Re: Performing Internal Calibrations - Dial gauges, micrometers, height gauges, calip

There are several levels of in-house calibrations, verifications, checks and etc.
There is a place for several levels of in-house checks, and cross checks.
The development of an in-house lab has a list of costs attached.
It might be possible to remove some measurement instruments from out-side calibration,
and have them marked as no-cal-required/indication-only.
As previously mentioned, a daily, weekly, monthly in-house check of some indication-only measurement devices is done.
It might be worth some cost analysis, and tool usage evaluations.
Some very low use tools might be stored, and others shared.


Starting to get Involved
Re: Performing Internal Calibrations - Dial gauges, micrometers, height gauges, calip

Thanks Sturmkind for the quick reply.
Using that stability method would be be a good way of determining calibration intervals but before that i really need to know whether I would need to setup an ISO 17025 lab in house or can we just perform calibrations on the above equipment ourselves without accreditation and just have traceability back to ISO 17025.


Inactive Registered Visitor
Re: Performing Internal Calibrations - Dial gauges, micrometers, height gauges, calip

The TS16949 and your written calibration procedures are sufficient in the world of automotive.


Starting to get Involved
Re: Performing Internal Calibrations - Dial gauges, micrometers, height gauges, calip

Thanks george,
I have looked into this and there are a number of instruments that we are looking at making for "indication only" and looking at sharing calibrated instruments rather than everyone having their own calibrated instrument if not needed on a regular basis. This will reduce the cost somewhat but we are still looking at calibrating as much as we can internally especially the above instruments as mentioned as we do have the grade 0 gauge blocks and slip gauges required which are traceable to 17025 calibrated standards. Would you recommend this route of calibrating with written calibration procedures under TS 16949 certification as Sturmkind has suggested?


Staff member
Re: Performing Internal Calibrations - Dial gauges, micrometers, height gauges, calip

Here is another thread on this subject:

Stijloor states that you should certainly develop a scope statement.:agree1:

I am not in the automotive industry, so I can't speak as such to the subject. I would state that while you don't have to pay the money to achieve accreditation under 17025, you should purchase a copy of it and develop a program compliant with the standard. It's a good procedure, and provides a good roadmap to address the management/technical consideration for operating a metrology lab.:)

George Weiss

Re: Performing Internal Calibrations - Dial gauges, micrometers, height gauges, calip

This is an expanding process with time/asset costs.
per 16949 you can have a lab, and 17025 accreditation is not required.
Are you planning on a room/lab for this, and having a cal-lab develop with some new STDs and temp/RH recorders in-place?
A temperature stabilized room might be found needed for a dimensional calibration area, depending on calibration expectations.
or are you going to bring your gage blocks to the areas of caliper/etc. use, and perform CALs in-house, but field service style?
large & complete In-house labs are a less common in high-tech companies.
If you have the gage blocks, (you do), and other required standards for checking of the calipers and other devices,
then in-house calibrations can be done.
Since many companies just outsource, I would look into exactly what the benifits and costs are.
It is like asking if more government regulations and agencies are good.
A good calibration provider is a nearly fixed cost. A UPS box or a field service call.
It might be that you could provide the calibration provider with a limited use scope for some devices, which would reduce cost.
It is automotive industry practice to have a supplier-guide, and this might be a place for such test limitations.
In-house calibrations will have a person overseeing calibrations, with a raised skill level and resquirements.
Some standards will still need outside service, (gage blocks etc.)
I view in-house calibration processes as a mixed bag.
It places more value on the in-house employee and his effectiveness.
My observation is that bigger business likes to place value on controled processes, and pay the end employee less.
This pushes for outside calibrations to structure costs.
With our ever expanding gobal economies, I am guessing that a very cost compedative calibration lab could setup shop,
and provide a 17025 service from halfway around the world, and have the item back in your hands via UPS/FedX.
The extent of inhouse calibrations would be value, which might slip away with lowering costs in the 17025 life-cycle,
and a sudden shift in your company's structure or priority(s).
A reflection on the use of the in-house calibrations might help. If your company wants to better control the calibration due dates,
and just-in-time calibrations, (which also saves money), over calling in a provider 1-to-2 months early to avoid out-of-cals ocurring.
You described 200 items. Does this mean there are another 200-300 items not being considered for in-house calibration?
The number of items you offer for outside calibration with determine the service contract discount.
You might jack-up the remaining calibration costs, by removing 40-50% of the items. (a real, and hidden cost).
An in-house calibration plus, is the hands on evaluations done by process people.
This is a type of involvement which gains process buy-in.
There is the conflict of interest comment in calibration standards.
Calibrating your equipment in-house sometimes has acceptance bias.
So for me: In the end it seems cheaper in-house, but larger organizations with large calibration provider contracts,
in my area of observation, generally go for the blanket out-sourced calibration. It is my view, from a few observations,
that a small company will try to avoid the costs, ( a large $20,000+ price tag), by doing the work in-house, (with hidden costs).
In-house can lead to lower costs, and if handled well, I believe a better method.
Cross checks, and daily checks can be elevated in a 6month or 1year interval to 17025 aligned/compliant.
Your situation, company, people in place now, all will factor into the will it work well formula.
A univeral guide is doing it cheaper now or loose the business. LEAN-Quality
I write a book, I just put it out there. I hope it has some usefull pieces of guidance/info.
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Starting to get Involved
Re: Performing Internal Calibrations - Dial gauges, micrometers, height gauges, calip

Hi George,
That is a very thorough answer and exactly the kind of thing I was looking from the forum. It is brilliant to have such a resource available and to have people like yourselves so willing to give feedback as good as you do.
We plan to carry out the calibrations in the measurement lab that we use to perform our measurement. We will need to work on controlling the environment a little better within in this lab and we will have to develop our scope I propose that although a little more work is required to be compliant to 17025 I believe in the long run it will work out cheaper than bringing in a 17025 accredited laboratory to calibrate our instruments.
By the way, can anyone suggest a Calibration Management Software that will allow us to perform gage RnR, MSA's, record the calibration results into a database and also provide email notification on when instruments are due calibration. I have looked at Gage Pack and the free software Track pro but i was looking for something a little more substantial but without the requirement to spend too much. Any suggestions would be brilliant. Thanks again for all your help.