Torque wrench calibration

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Position the square drive of the wrench in a vise, making certainly that the body of the wrench is not contacting (just the square drive touches the vise).Ratchet the wrench to a horizontal position.

All right, firstly, how to execute the “micrometer” or “Click” type of torque wrench (the beam needle type is under that, but both start with the wrench held horizontal by clamping the square drive in a vice in such a way that solely the square drive is in touch with the vice).

Measure from the center of the square drive (is the same with the center of the fastener, the wrench could or could not ratchet approximately this same point).

You can check the center of the square drive by the point at which 2 diagonal lines from the corners of the square cross.Notice this length on the handle. Decide someplace favourable, like at an even number of inches nearly where your hand would be.

Notice this length in inches or feet, depending if your wrench is marked in inch pounds (in. lb) or foot pounds (ft lb). Obtain a weight, somewhere close the amount of force you might usually extert on the handle (say, 20 lb, or 40 lb).Multiply the length from the center of the square drive by the weight you will utilize.

If your wrench is a clicker type, adjust it to the number you found when you multiplied the distance by the weight (inch lb or ft lb). If it Is not the clicker type read the part on beam/pointer type wrenches.Utilizing bailing wire, hang the weight at the mark on the handle.

If the wrench clicks, lift the weight, relocate it closer to the handle, let the weight hang at the new position. You could start by moving it an inch or two, and determine if it still clicks.
If it still clicks, continue moving it nearer until it does not, and then step by step move farter out (aside from the vice) until you get the transition point between where it clicks, and where it does not.

Measure this length. This is a new length. You are able now to utilize the ratio of the new length, and the first (anticipated) length to find out a calibration factor.

In case the wrench did not click when you first tried hanging the weight, discover how much further away you need to hang the weight to make it click. Attempt to find the transition point. Measure this length.You will likewise utilize this length to check a calibration ratio.

Let:

Ts = the torque setting on the wrench.
D1 = distance measured first (to the mark you made)
D2 = distance to point at which wrench actually clicked.
Ta = actual torque the wrench is applying.

Therefore, if you adjust your wrench to a given torque value (Ts) the torque it is in reality applying is:

Ta = Ts x (D2/D1)

And, if you require a certain actual torque (Ta) applied to a fastener,you would adjust your wrench to a value generated by this equation:

Ts = Ta x (D1/D2)

Alright, place the wrench in the vise as described.Mark it at 24″ from the center of the square drive.

Get a 22 Lb weight.Set the wrench to 480 inch lbs or 40 ft lbs.

Hang the weight on the line.In case it clicks, relocate it towards the vice, if it does not, relocate it towards the free end (aside from the square drive).Discover where the threshold between where it wil & will not click is. Lets say that’s at 30 inches. Fine, the torque it applied when you first hung the weight was 480 inch lb.

The torque it took to make it click at that setting was 30 in. x 22 lb= 660 in lb (divide by 12 to get ft lb)

If you wish to apply a certain quantity, say 60 ft. lb.,Just multiply 60 by 24/30 (so 60 x 12/15 = 48)
So, to torque a bolt to 50 lb, set your wrench to 48 “and a hair” ft lb.

Actually, when you know the ratio (like 12/15 = 0.8) all you’ve to do is multiply the torque you want on the bolt by that number (0.8) to tell you what setting to put the wrench at.

The beam / needle pointer type torque wrench:

Mark the torque wrench handle at a noted length from the center of the square drive Multiply the length above by the weight. Now relocate the hang point of weight along the handle until the torque wrench needle is directing to the value of torque calculated above.

Measure the length from the center of the square drive to the point that the weight is now hanging, and that is the the other length . These 2 lengths will be utilized to compute a calibration ratio.

Let:
Ts = the torque that you will read on the pointer
D1 = the initial distance to apply the actual torque
D2 = the distance to make the needle point to the value calculated
Ta = the calculated torque from the cosen distance X known weight.



One Response to “Torque wrench calibration”

1. Cyrus Parlan says:

   I would like to know how to determine the value torqued at 20% of range.

   Ex. Can i use 50-100ft-lb torque wrench to tighten 50ft-lb bolt.?

   Thank you