How are you calibrating your calipers, and rulers?

How are you calibrating your calipers, and rulers? Do these measuring instruments need to be certified?

I've never had it come up before, but on a related topic, I've always been surprised no auditor has queried calibration of stopwatches used in the verification of CCPs. Afterall, the critical point is temperature and time, so if the thermometer has to be calibrated, why not the stopwatch? It could have something to do with the theory of relativity I suppose.

Calipers and similar measuring devices are normally checked against certified Gauge Blocks. These are as they sound blocks of metal or plastic of a know certified thinkness. When a caliper is applied to them it should read the indicated thickness of the block within a specified tolerance. They can be used for micrometers and indicators. Simply Google Certified Gauge Blocks and you will see.

Thinkness / length, as a variable is usually not what you associated with a critical attribute of food safety but I'm sure there are cases. Just ensure you need to calibrate , check or certify these devices. Gauge blocks can be expensive depending on the Class etc. For coordinate measuring machines they are essential. For quality control they certainly have a role - not so sure for food safety applications.
I would love to hear what you are measuring....

G

Normally in China, caliper is used for measuring and calculating the overlap rate of tin canned product. Thus in my country it is usually a CCP monitoring device. So calibration, verification or regual checking is very important in my country. Just as G posted, we uses similar system for caliper calibration. Use a standard calibrated block.


BR
Jason

Normally in China, caliper is used for measuring and calculating the overlap rate of tin canned product. Thus in my country it is usually a CCP monitoring device. So calibration, verification or regual checking is very important in my country. Just as G posted, we uses similar system for caliper calibration. Use a standard calibrated block.


BR
Jason

Dear Jason,

Interesting. I thought it was normally obligatory to use a micrometer, eg

http://www.inspectio...oi/chap4e.shtml

(Although i hv also encountered much more approximate methods which had predictable economic consequences.)

Rgds / Charles.C

+1 for gauge blocks to certify calipers. Extremely simple to use and effective. They do need to be certified based on use, usually once a year minimum. Also, there are some handling considerations as the oils on your fingers can cause rust depending on how they are stored / used.

For rulers, I used a certified 1000 mm ruler as a master then checked production rulers to it. For what I was measuring, it was fine and held up to my systems / certification audits.

Good Luck!

I use calipers to verify a screen size. My brand is Starrett. I send them back to the manufacturer every two years for re certification. I keep this certification on file.