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In the Shop

RSS By: Dan Anderson, Farm Journal

As a farm machinery mechanic and writer, Dan brings a hands-on approach that only a pro can muster. Along with his In the Shop blog, Dan writes a column by the same name as well as the Shop Series for Farm Journal magazine. Always providing practical information, he is a master at tackling technical topics and making them easy for all of our readers to understand. He and his wife, Becky, live near Bouton, Iowa.

Torque Wrench Tips

Dec 18, 2013

 There's no need to use a torque wrench to tighten 99 percent of the nuts and bolts on farm equipment. But if you work on engines, transmissions, final drives or other assemblies that require or benefit from fasteners being torqued precisely, here are a couple tips;

-Always grip a torque wrench in the middle of its handgrip when pushing or pulling to tighten a fastener. Torque is calculated based on the distance from the pivot point of a torque wrench to the center of the handgrip. Pulling or pushing from anywhere on the handle except for the handgrip gives a distorted torque value.

-Don't jerk or lunge against the handle of a torque wrench during a "pull." Torque wrenches give their most accurate readings if the wrench is pulled smoothly and steadily. 

-Try to arrange so the torque wrench clicks or beeps (indicating desired torque value has been reached) in the middle or toward the end of a slow, steady pull of the handle. It takes more torque to start a bolt turning than it does to keep that bolt turning. So if you have limited room in which to swing the torque wrench handle, and have to reset the wrench, be suspicious if the wrench clicks or beeps in the first few inches of the fresh pull. In that case, the wrench is probably signaling the "breakaway torque" of the bolt rather than it's actual turning torque. Most common bolts can be safely loosened then re-snugged, with the goal of getting the wrench to click in mid- or late-pull. The exception is when tightening "torque to yield" bolts, which are special, one-time-use bolts that should never be loosened and re-used after they've been tightened to full torque value.


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COMMENTS (6 Comments)

JD Tech
Folks, Frank makes an excellent argument. I did some checking, and have posted a correction as a blog. Thanks, Frank for helping me keep things as accurate as possible!
6:27 PM Jan 3rd
Frank - Worth,, MO
JD Tech, I agree with you 100%. My point is that the pivot point doesn't 'care' where you grip the handle. A torque wrench is not made for the purpose of measuring the force applied to the handle, but rather the force applied to the nut or bolt being tightened to the click point. Granted, if you tighten beyond the click point, then more leverage would make it much easier to pull the handle and therefore much easier to overtighten....but, that would defeat the whole purpose of using a torque wrench.​
8:40 PM Jan 2nd
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