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What tools need to be calibrated?

What tools need to be calibrated?

What tools need to be calibrated?

Manufacturing Company. Recently, my company wants me to have a list for yearly tool calibration.
I listed all items like Caliper, micrometer, Dial Indicator, High Gage, Digital Multimeter.
And my boss suggest others should be calibrated too: Pin Gage, Gage Block, V-Block, Angle plate and even 36" steel ruler and Roundhead SPI Protractor (SPI 30-394-1).
Do they need to be calibrated? Yes, I am using them for inspection. My boss just worries about UL auditor or an ISO9000 can stop the company because those tools were not calibrated. Do we have any information about what tools need to be calibrated or not need to be calibrated? Thanks.


RE: What tools need to be calibrated?

Your calibration system can be however you wish to define it.  UL and ISO are primarily interested in you following what you have indicated (through documentation) your procedures to be.  In my opinion, if you are using items for inspection purposes and therefore making determinations/dispositions based on the measurements, you should be using a calibrated device in the appropriate environment.  The calibration interval is up to you but include the interval in the tool/instrument list.


RE: What tools need to be calibrated?

Yes, they need to have their calibration confirmed. Also, all measuring instruments used by other departments (whether company owned or not) should also be in your calibration programme.

Now as for the frequency, it is up to you.

Dave D.

RE: What tools need to be calibrated?

Calibrate a steel ruler?? I have had ISO auditors lok at me pretty funny for calibrating stuff such as rulers,tape measures.For anything basic, such as a ruler I would put a limitation on it, ie.. calibrated at first use and then only if damaged (no regular interval), or at first use then replace after two years.
How would you calibrate a ruler, is there a standard that you can have it calibrated to?

PSE is correct, if your quality program says that it needs to be calibrated then you better, but if it doesn't then you don't have to.

RE: What tools need to be calibrated?


Are steel rules used in the measuring of product? If so, yes, they need some sort of calibration confirmation.

I probably would do what you mentioned. On the initial confirmation of calibration I would use a vernier caliper that has had its calibration confirmed, then set it at different dimensions for linearity. Measure it with the steel rule or tape and read the measuring instrument (rule or tape). If it is within your calibration tolerance - great. Otherwise it is rejected.

After that initial confirmation, check for wear and damage only.

I don't think that this is too painful.

I have seen people use a tape measure to measure a product and the tape measure was not readable or the ends were chewed up.

Dave D.

RE: What tools need to be calibrated?

In our shop, all devices used to make acceptance measurements are calibrated.  That includes all of the above mentioned devices.  For steel rules, we verify accuracy upon receipt, and then "calibrate" annually.  The calibration procedure for the rules just checks for damage and wear on the ends.  Quick and dirty - it takes longer to fill out the paperwork and update the computer than perform the "calibration".  I think it is important to include them in the calibration system to ensure timely recall for checking for wear and damage.

As dingy2 said, what out for personal devices such as tape measures that employees may bring from home and use in the shop.  If they are being used for acceptance of product they should be calibrated.

Other types of devices that you may have that should be considered for calibration would include:  block gages, comparators, feeler gages, levels, load cells, pressure gages, torque meters, weight scales.


RE: What tools need to be calibrated?

Thanks for all of your inputs.
I think that it waste money to send those tools to calibrate and the guy who calibrate them will laugh at us, steel ruler, tape measures, fillet gage, projector...

RE: What tools need to be calibrated?

Don’t know about a waste of money but the guy shouldn’t laugh at you.  

Maybe your boss knows something you don’t.  

If you have ever been in an argument about whether a $20,000 part was in spec by 0.001” or less you will be glad your tools are good.  

You never know how one measurement will ripple through a system.  The size of the boosters for the space shuttle was determined by an anonymous ancient roman.   Somebody standardized chariot wheels.  Chariot wheels made ruts in roads.  Wagons were made to fit those ruts.  Railroad tracks were made to fit the wagons and space shuttle boosters were made to fit on railroad cars.   Read Connections by James Burke or watch the PBS series to get an idea of how this works.   

Have a one meter rule calibrated and keep it under glass and lock.  Use it annually to calibrate tapes and everything else.   

You might also consider the fact that maybe your boss and folks who have been around a lot longer than you may know something you don’t.  It may not always be true but it is a pretty good way to look at things.  

Finally, the rule to measure twice and cut once doesn’t work if your tape is bad.  


Thomas J. Walz
Carbide Processors, Inc.

RE: What tools need to be calibrated?

I will add my 2 cents. Calibrate them all!!! With Iso or QS you can never be too safe. With Tapes and Steel Rulers you can do them in house with calibrated gage blocks. Gage Pins and Block should be sent out once a yr (unless not used much then 2-3 yrs). Gage pins and block used every day should be on a 1-3 month cycle due to wear that can happen.

RE: What tools need to be calibrated?

Send one tape out to be calibrated, and never use it for production but rather to check all the other tapes against.


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RE: What tools need to be calibrated?

I appreciate all your inputs. Thanks.

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