How to Make Your Own Torque Wrench
When you are a do-it-yourself ...er..., sometimes you may have to improvise the tools that you need. For example, let's say that you are tightening the nut on a wheel, axle, brake caliper, or any torque crucial component of a machine, and you don't happen to have a torque wrench at your location, or don't have the money to buy one. This is where your improvisation becomes your tool.
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Things You'll Need
- Spring scale (such as a fish scale)
- Any wrench (preferably a breaker bar and socket)
- Strong wire, such as baling wire
- Distance measuring tool (such as a tape measure)
Instructions
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1
Attach your scale to the end of your wrench with baling wire (or other STRONG wire). It is important that it be securely attached as far away from the drive portion of the wrench to provide the highest maximum torque.
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2
Measure the distance from the center of rotation of the fastener (in the case of a ratchet or breaker bar, this would be in the middle of the drive head) to the point that your spring scale is attached to. This measurement can be done with a tape measure or ruler. Write down your measurement in the unit that corresponds to the torque specification that you have. For example, if you are trying to torque a nut down to 75 ft lbs, and you measure 16 inches in this step, then write down 16/12 (or 4/3) feet.
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3
Now, use a calculator or pen and paper to divide the target torque by the distance measured in the previous step. For example, if your target torque is 75 ft lbs, and you measured 4/3 feet, then 75 ft lbs/(4/3 ft) = 56.25 lbs.
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Take your wrench and scale setup and place it on the nut or bolt. Then, with the scale perpendicular to the wrench, pull on the scale (use a thick glove or other tool so that you don't hurt your hands) slowly until the scale reads the number in lbs calculated in the last step. Do not exceed this weight on the scale, take your time. This method can be a little bit of a pain, but in a pinch, it will help ensure that you get things done right.
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Tips & Warnings
If you're in a real bind, and don't have any sort of scale, if the fastener you are torquing puts your wrench in a vertical plane, you can use weight instead! Attach an appropriate amount of weight at an appropriate distance from the center of rotation, and in a pinch, you can let this calibrate your torque!
