Torque Wrench Calibration Frequency (Calibration Interval)

MarilynJ6354

Involved In Discussions
#1
We use torque wrenches very infrequently for certain overhead doors that require their use. Each of our 12 facilities may have up to 10 for each service tech. The calibration labs say they must calibrate annually. However, this is costly and some are not even used once in a year. Aren't we able to tell the lab the desired interval of calibration? If not, how do we get around doing this every year and still be ISO compliant?
 

Marc

Captain Nice
Staff member
Admin
#2
Re: Calibration of Torque Wrenches

Your calibration frequency should be based upon the calibration history of the device. For example, if they were calibrated last year and the year before and no adjustments were needed, and all were within tolerance, extend your cycle to 1.5 or 2 years. If they are then calibrated again and the same thing happens (no adjustments were needed and all were within tolerance) you might want to extend it further.

The only draw back is that one could be damaged (such as dropped and knocked out of calibration but not visibly broken) and no one would know it until the next calibration date. Now the question becomes "How critical is the torque requirement?"

Your calibration laboratory (I assume you use an outside laboratory) can recommend a calibration frequency, but it is up to you to tell them what you want and when.
 

MarilynJ6354

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#3
Re: Calibration Frequency of Torque Wrenches

What do you mean by "How Critical is the requirement?" We didn't calibrate them in the past but an ISO auditor said since we use them on doors for customers, they have to be calibrated. It doesn't make sense to me to do it if they are used so infrequently.
 

MarilynJ6354

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#4
Re: Calibration Frequency of Torque Wrenches

I found this, which means we should calibrate about every 20 years!

How Often to Calibrate the Tool
The frequency in calibrating the torque wrench depends on the user and on the frequency of use. There are no strict standards that are being followed for the frequency of calibration. However, it is useful to know that the readings have a tendency to change between 2500 to 2800 repetitions. Hence it is recommended that you calibrate your wrench when you have made 2500 repetitions.



Read more: http://www.doityourself.com/stry/knowing-how-often-to-calibrate-your-torque-wrench#ixzz0t7hhxAJt
 
#5
Re: Calibration Frequency of Torque Wrenches

We use torque wrenches very infrequently for certain overhead doors that require their use. Each of our 12 facilities may have up to 10 for each service tech. The calibration labs say they must calibrate annually. However, this is costly and some are not even used once in a year. Aren't we able to tell the lab the desired interval of calibration? If not, how do we get around doing this every year and still be ISO compliant?
You don't calibrate torque wrenches! Get a calibrated torque setting master - (beg, borrow or steal it) and do a torque study. Do it by wench type/make and range (if they are adjustable). Do a proper SPC style study and see how well the wrenches repeat the torque values. You may have to do a small sample of each wrench type in a few months to see how 'stable' they are to back up the reasons for not doing it again for a long time.

I've seen someone who did this very well. It saved them a packet. They also had a bunch of different torque wrenches, because they bought whenever they needed them, not think much about anything but range and price. Guess what they found when they did the study? The clicker style, especially the Snap-on ones, were simply the best! But they also had a bunch of beam style ones which they had to get rid of...
 

Marc

Captain Nice
Staff member
Admin
#6
Re: Calibration Frequency of Torque Wrenches

What do you mean by "How Critical is the requirement?" We didn't calibrate them in the past but an ISO auditor said since we use them on doors for customers, they have to be calibrated. It doesn't make sense to me to do it if they are used so infrequently.
Is there a documented customer or product requirement for the torque of what ever it is you are tightening? If there isn't the auditor was blowing smoke in your eyes.
 

MarilynJ6354

Involved In Discussions
#7
Re: Calibration Frequency of Torque Wrenches

We are a service company with no one in house to do SPC studies, calibrations, etc.
 

MarilynJ6354

Involved In Discussions
#8
Re: Calibration Frequency of Torque Wrenches

Our equipment service manuals just give a torque amount and that's it. No customer has requested it (these are dock doors) and no manual states that we must use a calibrated torque wrench!
 
#9
Re: Calibration Frequency of Torque Wrenches

Our equipment service manuals just give a torque amount and that's it. No customer has requested it (these are dock doors) and no manual states that we must use a calibrated torque wrench!
Well, yeah..but:

What risk do you run by not knowing what the item is torqued to? Maybe the customer doesn't know any better. Would it cost you to have to go back and do the job over? Servicing doesn't relieve you - necessarily - of the responsibility to know the job's done correctly. As an example, Xerox copiers are (somewhat) similar. You (the customer) don't care about the torque, but the tech will tell you, if certain fasteners aren't tightened, there can be service issues later. The manual says 'torque to x' - it's implied, that the wrench can achieve the value - and you get that through setting it (and the capability study)

The auditor was kinda off base, however there's some opportunity here to show you have control over a process and reduce the risk of it being/going bad...
 

Marc

Captain Nice
Staff member
Admin
#10
Re: Calibration Frequency of Torque Wrenches

If your service manual gives a torque specification, there is (or was at some time) a reason for it. You mentioned: "How Often to Calibrate the Tool
The frequency in calibrating the torque wrench depends on the user and on the frequency of use. There are no strict standards that are being followed for the frequency of calibration. However, it is useful to know that the readings have a tendency to change between 2500 to 2800 repetitions. Hence it is recommended that you calibrate your wrench when you have made 2500 repetitions.
"

See post 2 in this thread for my thoughts. Once your torgue wrenches have 3 calibrations you should be able to determine whether you can extend the calibration frequency. I have seen some measurement equipment that had 10 year calibration cycles. They were rarely used, but the company could show stability by showing old calibration data.
 


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