Internal Calibration of Torque Wrenches

[s.starr]

At our manufacturing plant, a majority of the torque wrenches we use are click-style adjustable, with some digital-style adjustable. Unless the tool manufacturer says otherwise (rare), we use the rule-of-thumb 1-year or 5000 clicks until they are shipped out to be externally calibrated. Usually, the calibration due date is documented and followed as well.

We have torque testers in house to verify the torque wrenches are still calibrated. My question is, how often should we be checking our torque wrenches in house to see if they are still within their calibrated targets? We always check them if the tools were dropped or damaged, but I'm looking more for a routine that is reliable and value-add.

 

[Ed Panek]

It depends. What happens if you find a torque wrench is out of tolerance "As found"

 

[Randy]

Aviation - Prior to use & recorded on a sheet. (At least in the military, civilians might be a bit more slack)

I commonly see prior to daily use and recorded when I'm auditing.

 

[Miner]

We used torque drivers vs. wrenches but checked them on a torque analyzer at the start of each shift and after breaks and lunch.

 

[John Predmore]

how often should we be checking our torque wrenches

Frequency of verification is a tradeoff between the cost to verify (including labor time and hassle) versus the cost (in terms of bad outcomes) of a out-of-tolerance wrench used for product conformity decisions. You are the best person to evaluate that tradeoff for your organization. Part of the discussion is what is the failure mode (gradual or sudden) and how to improve your firm's ability to detect an out-of-tolerance situation? One scientific approach to the question is to start with frequent verification checks, collect torque reading data, and lengthen interval based on prediction from trends in the data.

p.s. One guideline that is often neglected is the manufacturers of click torque wrenches recommend to back-off the preset spring force to zero when the wrench is not in use, to prolong their service life.

 

[dwperron]

At our manufacturing plant, a majority of the torque wrenches we use are click-style adjustable, with some digital-style adjustable. Unless the tool manufacturer says otherwise (rare), we use the rule-of-thumb 1-year or 5000 clicks until they are shipped out to be externally calibrated. Usually, the calibration due date is documented and followed as well.

We have torque testers in house to verify the torque wrenches are still calibrated. My question is, how often should we be checking our torque wrenches in house to see if they are still within their calibrated targets? We always check them if the tools were dropped or damaged, but I'm looking more for a routine that is reliable and value-add.

What is acceptable risk of failure to your organization? When would having to recall product become unacceptable - a shift / a day / a week / a month? That is what should be accounted for in setting retest cycles.
How about the results of different users for the same tool, should you take that into account?

If you are verifying your torque wrenches with calibrated torque analyzers then why do you calibrate in addition? You are maintaining traceability. I don't see any reason to calibrate a wrench unless it fails the verification.

 

[shutch]

I am an "In house Calibration Tech." Here we use torque wrenches in our assembly department. The rule of thumb is we check each click style torque wrench in house every 6 months or when there has been a drop/concern on the Veritorq. Otherwise the only time we send them out is if they are broken or otherwise non-conforming for repair.

The torque tester (Veritorq) is sent into the manufacturer annually.