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Calibration - Buying New Tools - How do you determine the next calibration date?

L

LexieB

#1
Hi everyone,

I am having a hard time finding anyone agree on how to handle calibration in general, so I thought I'd turn to you.

I'm in precision machining, so we have all the standard stuff: calipers, thread/pin/height gages, micrometers, etc.

Question: When we buy a new tool and it comes with a certificate (in this case a caliper), how do you determine the next calibration date? There is no date on the certificate, I'm assuming this certificate was issued at the time of manufacture. I don't know how long it was sitting on a shelf or how that works. Should I just put the date we started using it?

Thanks!!
 

BradM

Staff member
Admin
#2
Re: Calibration - Buying New Tools

That's a really great question.

In general, I usually follow the practice of calibrating/testing everything once it hits our door. There are way too many variables involved with new instruments.


  • When did they test it?
  • Was it a calibration or a conformance?
  • Where was it calibrated, and where was it sold?
To your question, I would date the next calibration due to fit in with the interval that is required for that particular instrument. If you are going to accept the certificate on face value, just set the recall date to your liking.
 

somashekar

Staff member
Super Moderator
#3
Re: Calibration - Buying New Tools

Hi everyone,

I am having a hard time finding anyone agree on how to handle calibration in general, so I thought I'd turn to you.

I'm in precision machining, so we have all the standard stuff: calipers, thread/pin/height gages, micrometers, etc.

Question: When we buy a new tool and it comes with a certificate (in this case a caliper), how do you determine the next calibration date? There is no date on the certificate, I'm assuming this certificate was issued at the time of manufacture. I don't know how long it was sitting on a shelf or how that works. Should I just put the date we started using it?

Thanks!!
If you have your internal procedure and facility for calibration, it is always good to route any new instrument through this and generate your report and from then on mark your frequency based on your handling and usage method.
 

harry

Super Moderator
#4
You can look from the 'risk' angle. If the risk is high, have it calibrated just to make sure. Otherwise, it is good practice to perform verification before you use it. The possibility of a new and calibrated instrument being 'out' is slim but there were instances. The same may be used for determining calibration frequency/date.
 
Last edited:
J
#5
All good responses.
I can tell you that, when I handled calibration, new tools were quickly checked for verification, logged, tagged with the next appropriate date for that type tool and issued for use.
Our work was not particularly "precision" work and this system worked fine.

I am curious as to why there is disagreement about this.

Peace
james
 

bobdoering

Stop X-bar/R Madness!!
Trusted
#6
Determining the next calibration date is not a rubber stamp affair. You need to have an idea of its use. If you are going to use it in a grinding area, and they are notorious for not adequately cleaning the part before measuring it, then you may need to do 3 month intervals - especially for calipers, since they do not have hardened faces like micrometers. Micrometers will wear in that environment, though. You should have an idea on how well previous gages did in the past in similar usage. Gages used with greater usage frequency - especially 100% - may also need more frequent calibration. So, the reason why you will not hear an agreement is because the correct answer is IT DEPENDS! There is no standard frequency for those very good examples above. All gages wear at different rates, depending on their design, material and use.
 

jkuil

Quite Involved in Discussions
#7
The frequency of calibration is best to be determined by the equipment owner in consultation with the technical department that performs the calibration. The frequency is determined by assessing following aspects:
  • What are the risks involved with the equipment being OOT, the higher the risk the shorter the calibration intervals;
  • Expected drift in accuracy and precision based on technical characteristics of the equipment; experience with identical and similar tools; recommendation by the supplier;
  • Itensity of equipment use: the more frequent the equipment is used, the shorter the interval.

It is recommended to reconsidere the calibration interval:
  • In case of an OOT, also considering the history of OOTs;
  • Periodically by statistically analysing the trends in accuracy and precision. It may even de justifyable to increase the interval, therefore saving calibration costs

A calibration needs also be performed:
  • As part of the qualification of new equipment: prior to PQ
  • Before and after significant replacements of the equipment
  • And before decommissioning
The calibration before replacement or decommissioning of the equipment is to provide documented evidence that the equipment was in its validated stated up and until the last usage.
 
G

gagegirl

#8
Hi. My company is also in precision machining. Our practice is to calibrate all new tools/gages before use. Once that is done and the new tool/gage is in your calibration system is should fall in with all other like-type tool/gaging.
Also, check your customer requirements and specs, they will usually tell you what they expect. Our customers dictate our calibration frequencies.
 
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