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Using Caliper A to verify Caliper B - Verification of Calibration

Q

QAMTY

#1
Hi everybody

while defining the calibration and verification under 7.6 Control of monitoring and measuring equipment.

I have the following equipment:

1 caliper 150 mm named A

1 steel rule "Moore & Wright ER424" with 0.5 mm resolution
1 caliper 150 mm named B
1 micrometer.

In order to comply to standard, I sent all the equipment to an external supplier for the calibration and I have the certificates.

I have a print shop business, in fact we dont need tight tolerances
I accept +/- 1 mm in my product, in the past I have not had quality problems due to bad measurements.

Normally I use for inspection of the product the steel rule
The micrometer is used to measure sheets of paper and caliper is used to measure some ancillary equipment.

At this time I comply with calibration, but not for verification, for that, I have an idea.
The caliper A is a spare caliper, in case of failure of caliper B, the A is kept in a secure place and only will be used in such case.
Verification are planned every 6 months.

Question

Could I use the caliper A to verify caliper B, say measuring one part and comparing results, if such results fall within +/-1 mm, my caliper B is ok?
The same task it can be done with the micrometer, compared against caliper B, I dont want to spend money in gage blocks.

For the steel rule, I will only do visual inspection, (legible marks, numbers, etc.).

Other option it is not to verify the equipment and wait every year for the calibration of them, since our place is clean, measuring equipment is not
too much used, personnel take care of them, additionally my tolerances are not too tight.

Please shed light on me, give me some input

Thanks
 

hogheavenfarm

Quite Involved in Discussions
#2
Re: Using caliper A to verify caliper B, under ISO 9001 2008

I do something similar, I have a numbered level assigned to calipers used in different areas. Quality lab calipers are "-01" engineering is "-02" and shop is "-03". A 03 shop caliper can be calibrated agianst an 02 or 01, but not another 03. I use this all the way up the chain. QA calipers are calibrated against the gage blocks directly.
 
#3
Given the tolerances are loose, you could also just select a gage master.

You don't have to verify a caliper against an EXACT gage block.

You could, now that your equipment has been verified, measure some random block of steel laying around (with the obvious requirements of parallel side to side with no burrs).

Let's say your newly calibrated equipment agrees that this gage block is 12.85 mm thick. Now, you have a "master." It would be better if you had two, with significantly different values.

Label them, store them in a controlled location.

Any time between now and your next calibration, you can check your masters and know that your gages are still calibrated.

Calibration is all about measuring a known object with a study device and demonstrating the study device gives you the expected response. It does not have to be any certain size.
 
#4
Given the tolerances are loose, you could also just select a gage master.

You don't have to verify a caliper against an EXACT gage block.

You could, now that your equipment has been verified, measure some random block of steel laying around (with the obvious requirements of parallel side to side with no burrs).

Let's say your newly calibrated equipment agrees that this gage block is 12.85 mm thick. Now, you have a "master." It would be better if you had two, with significantly different values.

Label them, store them in a controlled location.

Any time between now and your next calibration, you can check your masters and know that your gages are still calibrated.

Calibration is all about measuring a known object with a study device and demonstrating the study device gives you the expected response. It does not have to be any certain size.
Although the process described above is functionally correct, it fails in one area - there is no traceability to a NIST (or equivalent) standard. Not sure if this is important to you or not - in your line of work I would not expect that it is.
Another option is to purchase several individual gauge blocks - the prices are not as steep as you might think. As long as you have the calibration certificates for THOSE (and calibrate them at a frequency that YOU feel is appropriate) then you are covered.
 
R

randomname

#5
Using your own blocks for Verification between annual Calibration intervals would likely be fine for your application.
 
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