For the Mathematicians:
I have a torque wrench that will only measure as high as 150 ft-lb. I need to torque a couple bolts to 300 ft-lb. I don't want to buy another torque wrench that will measure that high because I don't ...
Forum Discussion
dieharder wrote:
Bottom line... no bar added to the handle is going to help you get 300# out of a 150# wrench.
A torque multiplier does not increase the required force applied to the actual wrench. From the Snapon website:
" The gear train increases the mechanical advantage of a ratchet in direct proportion to the gear ratio of the multiplier. For instance, using a GA184A torque multiplier, which has a gear ratio of 4.0:1, and then applying 100 lb. ft. of input, the result will provide approximately 400 lb. ft. of torque to a threaded fastener."
Just google "how torque multiplier works" for lots of explanations. It's conceptually sorta like a rope and pulley setup... You cannot add a length of pipe to a torque wrench to increase it's range and if you do that and force it past it's max. scale reading, you WILL damage it. Torque wrenches are finely calibrated instruments and should be treated with respect. Also note that there can be up to around 10-15% torque loss in a multiplier from internal friction.
If you think you may need to do 300 more than once in the long run, go to HF and buy a larger torque wrench or find a good used one on CL. Or rent one. Or go to a shop somewhere that can do it, which likely won't cost much, if anything. A torque multiplier isn't cheap either. I paid under $100 for a new 300# torque wrench (hecho en China). I needed 360 lb-ft. on a pitman arm on a steering box once and went to a shop that works on semi-trucks and they didn't charge anything to torque it up. If accuracy is important, always use the correct tool.
*If* you are out in hinterland, you *could* rig up say a 4' to 8' 2x4 or 2x6 or length of pipe and hang some known weights off the end like bricks, bags of flour or whatever. Torque is simply length times weight. I measured the breakaway torque in a limited slip differential once by using a long pipe and adding weights.
