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====== REF: Tools & Fasteners ======

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====== Torque Wrench Field Calibration ======

====== Field Calibration Check ======

If you need to know for sure whether your torque wrench is calibrated correctly, you can take it to a professional to have it checked. \\
However, here’s a quick field check you can do yourself on a click type torque wrench: ((https://www.tekton.com/torque-wrench-accuracy-and-calibration)) \\
__This is not to be considered a professional calibration__. Reason being, there are several factors that can result in errors in testing. \\
The length measurement can be off depending on how you measure that. \\
The weight of the wrench can affect the reading. \\
Bouncing the weight on the handle will change the results. \\
The weight pulls differently on the handle if the wrench is allowed to turn sideways in the vise before or during the test, changing the results. \\
__There is nothing scientific about the test value or weight used__. \\
If you choose a weight lifting weight marked 20 lbs. Is it really 20 lbs or a little more or less? \\
If you weigh the subject weight beforehand, are your scales accurate? \\
If the calculation comes out to a decimal point, how will you set that on the analog scale? \\
You also have to trust your eyes when setting the torque value on the wrench. This can also be variable depending on your eyes. \\
All that said, below is the testing procedure. \\
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  - **Exercise the wrench before testing**.
    * Turn the handle up and down the scale to allow internal lubrication to work on the moving parts before testing.
    * This also aids in settling of components into their working position. 
  - **You'll need a weight to hang on the torque wrench and a string / rope to hang it with**.
    * The more the weight, the higher torque range at which you can test the wrench. A 20 lb. weight seems to be an average (easier to handle).
    * Be sure to weigh both the dead weight and the spring / rope together to get total weight hung on the wrench. \\ The more accurate that weight measurement is, the more accurate your test results. \\ It'd be good to use a couple different weights in the average torque range you'll be using the tool.
    * An 18 lb. weight was used in the example below.
  - **Measure a length in inches on the wrench handle**:
    * You can measure the center of the wrench or find a measure farther down the handle. \\ The exact point of measure is not as important as the measurement number itself.
    * Measure the distance in inches from the center of the drive square down the handle. \\ Use a marker or a piece of tape to mark the handle for your test weight point.
  - **Calculate the torque value and set the wrench**:
    * Set the torque wrench to the total weight of the objects you will hang on it multiplied by the number in length.
    * In the example below, an 18 lb. weight was hung on a ft/lb torque wrench with a test length of 8 inches.
      * Calculate: 18 lbs. of weight x 8" of length = 144 in/lbs.
      * Since this wrench measures ft/lbs, convert 144 in/lbs x .0835 to get 12.024 ft/lbs.
      * So for this example, 12 ft/lbs will be used since the extra .024 will be impossible to find on the scale on the wrench.
  - **Chuck the drive square in a vise**:
    * Let the handle hang (at 0 level position) \\ You can use a level to make sure the wrench is really parallel.
    * After clamping the square drive, you need to make sure that no other part of the torque wrench touches the vise.
    * Make sure the wrench is straight up and down (leaning sideways will change the test results).
  - **Hang the weight over the mark you made in step 2**.
    * Don’t let the weight touch the ground.
    * Set the weight slowly and easily on the wrench. \\ If you set it down hard, the jolt of weight on the handle will make it click in most conditions regardless of where you place it.
  - **Move the testing points**:
    * Your torque wrench is accurate if it clicks when you set the middle of the string / rope over the mark you made in step 2.
    * Set the weight over the mark.
      * If it clicks, ease the weight up and move it closer to the drive square. \\ It should not click there. \\ If it does, make a mark on the exact spot where it clicks.
      * If it doesn't click on the mark, ease the weight farther down the handle toward the end of the wrench until you find the exact point of click.  \\ It should not click there. \\ If it does, make a mark on the exact spot where it clicks.
  - **Interpreting the results**:
    * __If the wrench clicks on the mark you made in step 2__, your wrench is within calibration.
    * __If the wrench clicks higher toward the drive end than your mark__, your wrench adds more torque than what is on the handle's set value. \\ (you are putting more torque on a bolt than the value you set on the wrench)
    * __If the wrench clicks farther down the handle than your mark__, your wrench adds less torque than what is on the handle's set value. \\ (you are putting less torque on a bolt than the value you set on the wrench)

The test wrench below clicked 5/16" down the handle from the set mark. \\
The scale would have to be set to 12.518 ft/lbs to deliver 12 ft/lbs of torque to a fastener. \\
18 lbs weight x 8-5/16" length (8.3125) = 149.625 in/lbs. \\
149.625 in/lbs x 0.0835 = 12.494 ft/lbs. \\
(12.494ft/lbs + .024 ft/lbs subtracted for testing  =  12.518 needed to deliver 12 ft/lbs)

So in theory, with the test wrench set to deliver 12 ft/lbs of torque, it would have only delivered 11.482 ft/lbs of torque. \\
... Or, maybe the fish scale is out of calibration and the wrench is right. \\

|  Pick your weight ((photo by Hippysmack))  |  Set the wrench level in a vise  ((photo by Hippysmack))  |
|{{:techtalk:ref:tools:torque_wrench_calibration_1_by_hippysmack.jpg?direct&300|}}|{{:techtalk:ref:tools:torque_wrench_calibration_2_by_hippysmack.jpg?direct&300|}}|

|  Don't allow wrench travel to touch vise ((photo by Hippysmack))  |  Make a mark down the handle ((photo by Hippysmack))  |  Calculate torque value for wrench ((photo by Hippysmack))  |
|{{:techtalk:ref:tools:torque_wrench_calibration_3_by_hippysmack.jpg?direct&300|}}|{{:techtalk:ref:tools:torque_wrench_calibration_4_by_hippysmack.jpg?direct&300|}}|{{:techtalk:ref:tools:torque_wrench_calibration_5_by_hippysmack.jpg?direct&300|}}|

|  Gently place the weight on the wrench (don't let it bounce). Move the weight up and down handle to find point of click ((photo by Hippysmack))  |||
|{{:techtalk:ref:tools:torque_wrench_calibration_6_by_hippysmack.jpg?direct&300|}}|{{:techtalk:ref:tools:torque_wrench_calibration_7_by_hippysmack.jpg?direct&300|}}|{{:techtalk:ref:tools:torque_wrench_calibration_8_by_hippysmack.jpg?direct&300|}}|





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