Split-Beam Torque Wrench Calibration

[The Critic]

Curious if others can post the calibration certificates for their split-beam torque wrenches.

These wrenches are generally less accurate than other types; after all, you can only set the values in increments in 5 ft-lbs!

Snap-On and PI both advertise 4% accuracy. It looks like mine is pretty close to the 4% threshold.

 

[Bailes1992]

I remember working in an Aerospace facility where they repaired thrust reversers for GE jet engines.

Whenever they had brand new torque wrenches in, no matter the brand, no matter that they came with a calibration certificate, they were all re-calibrated in house and nearly every single one was out.

 

[atikovi]

they were all re-calibrated in house

And how were the re-calibrating tools calibrated? I mean, if you send off your wrench to be tested, how are the tools used to calibrate the wrench, tested?

 

[Spectre694]

And how were the re-calibrating tools calibrated? I mean, if you send off your wrench to be tested, how are the tools used to calibrate the wrench, tested?

If it's anything like our stuff it all has to be NIST traceable for the calibration.

 

[racer12306]

And how were the re-calibrating tools calibrated? I mean, if you send off your wrench to be tested, how are the tools used to calibrate the wrench, tested?

A full calibration facility needs to have accredited calibrations (ISO 17025) of their equipment. Increases the paperwork and provides extra information about the actual calibration including measurement uncertainty.

There are also general rules about having equipment that is x degrees more sensitive than the device being calibrated.

 

[redbone3]

And how were the re-calibrating tools calibrated? I mean, if you send off your wrench to be tested, how are the tools used to calibrate the wrench, tested?

Torque calibrators are calibrated with "torque arms" and weights. Basically a lever and a mass to make a known torque.

 

[RooflessVW]

I remember working in an Aerospace facility where they repaired thrust reversers for GE jet engines.

Whenever they had brand new torque wrenches in, no matter the brand, no matter that they came with a calibration certificate, they were all re-calibrated in house and nearly every single one was out.

As it should be.

 

[Soft Cars]

Why can't you post a picture of the entire torque wrench? What a tease.

 

[kschachn]

If it's anything like our stuff it all has to be NIST traceable for the calibration.

Yep, same. And our metrology lab had regular visits from a calibration service.

 

[haggler]

I had a 3/8 split beam Precision Instruments I was stupidly using to torque the wheels of my old car. It fell out of spec after a year or two because i was at 85-90% of the capacity of the wrench. I sent mine to angle repair in west virginia, harbor freight advertises them. In my own testing it was around 10-20% off (higher) using a digital torque adapter. Now its much closer to spec but I also noticed for good accuracy you should apply force from exactly the mark on the handle. I didn't pay extra for the certificate because I'm just a diyer.

 

[SubLGT]

Curious if others can post the calibration certificates for their split-beam torque wrenches.....

I don't have a photo handy, but this is my summary from an older post of mine, for a 1/2"drive PI split beam:

I received my 1/2" drive 50-250ft-lb PI split beam torque wrench back from the accredited calibration lab today. I bought the wrench summer of 2021 and have put less than 50 cycles on it. The wrench failed to meet its 4% accuracy specification.

At 50ft-lb, the wrench had an error of +12% !
At 150ft-lb, the wrench had an error of +4.3%
At 250ft-lb, the wrench had an error of +2.8%

After a calibration adjustment by the technician, all test values are now within +/- 1.0% at 50, 150, and 250 ft-lb

I also had a near new 3/8"drive PI split beam checked:

The wrench failed to meet its accuracy specification of +/- 4%.

The torque error at 120 in-lb was +5.39%
The torque error at 360 in-lb was +4.29%
The torque error at 600 in-lb was +2.08%

After the technician adjusted the calibration, the error values are:

The torque error at 120 in-lb is now +0.99%
The torque error at 360 in-lb is now +1.20%
The torque error at 600 in-lb is now +0.52%

 

[Wheel]

Yours looks like it has closer tolerances than mine...