I'm not sure my torque wrench is working correctly. Anyway to check them.

 

you need another one, preferably a beam time and check one against the other...course you need a 1/2" adapter

 

If you live near a Costco, stop by the Tire center. Each Shop is equipped with a torque analyzer for checkingthe accuracy of their torque wrench. If you ask the manager nicely he may let you check the accuracy of your wrench ( I would...)

 

There is equipment made specificaly for checking torque wrench accuracy. It's expensive. Checking one against another is only useful if one of them is already known to be accurate. If both of them are off, then your test is invalid.

 

They can be calibrated for a nominal fee. Look up local companies that do calibration of measuring equipment. In dallas I used HP, they were right down the street, Plano actually.

 

you know an easy way to check is to find the torque specs for a bolt and then tighten it until it breaks.....the breaking point is approximately twice the torque spec

 

if it's a craftsman, they will do it at a craftsman repair center.

 

Here's a fundumental method for checking a torque wrench...

http://home.jtan.com/~joe/KIAT/kiat_3.htm

 

This approach is way too crude to calibrate a torque wrench.

You can calibrate a torque wrench using a vise and a known weight.

Clamp the drive of the torque wrench in your vise so the handle is horizontal +5 degrees, - 0 degrees.

ACCURATELY weigh some thing you can hang from the center of the handle that is about 25% to 50% of the full range of your wrench.

Measure the distance to the center of the handle and hang the weight at that point.

The torque reading should match the weight in pounds times the length in feet from the drive to the point the weight is hung.

For example if your wrench measures 18" to the center of the handle, has a full scale reading of 100 ft-lbs, you would find a 30 pound weight, hang it, and read 45 ft-lbs (18"/12" = 1.5'; 1.5' times 30 lbs = 45 ft-lbs) on the dial or beam. If it a click type, you'd set it at 45 and see if it just clicks when the weight is applied. If not you'd go up or down in 1 ft-lb steps until it clicks when the weight is applied to the wrench.

If you want to be seriously precise make sure the handle is horizontal when the weight is on the wrench.

 

thats pretty neat....why is it the center of the handle as opposed to the end or the length of the wrench???

 

the next question becomes -----, if the torque wrench does need to be recalibrated, then how is it done?

 

 

We never used or calibrated beam type wrenches. The snap over or click type wrenches can be calibrated by ddjusting the spring inside. It became part of our calibration procedures for ISO certification, was kind of a PIA but it really made a difference in failure rates.

 

The length that you choose to measure from should be arbitrary....What you are looking at is the moment arm of the wrench....Mo=Force*distance..the easiest distnce from the center would of course be 12' inches (1 foot) for a reading in ft/lbs.....

As far as actually changing the calibration of the wrench......???

 

This is to answer the question:

"Why use the center of the torque wrench handle?"

Because the actual torque generated is the force times the lever arm. Most wrenches are designed to be used from the middle of the handle. To illustrate, if the handle were 2' long, 18" to its center, putting a 30 lb weight in the middle of the handle would yeild a torque of 45 ft-lb, towards the front (nearer the drive end) the torque would be 15 ft-lb, and finally at the extreme end the torque would be 75 ft-lb.

That is why you need to use the middle of the handle. This is really an issue when you use offset extensions (the kind you need to torque the center intake manifold bolts around the choke heat stove), since you use the equation:

Output Torque = ((A+B) * Wrench Setting)/B

or

((Output Torque)*B)/(A+B)=Wrench Setting

Where A = offset length of adaptor in feet
Where B = torque wrench length to center of handle from square drive

"Output Torque" is the torque applied to the nut or bolt and "Wrench Setting" is the reading or setting of the torque wrench.

 

That's a good way to check 'em. The name brand beam type are very accurate.