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Broken U Bolt On Hitch

Last updated on April 7, 2008

This is what happens when one uses a torque wrench expecting it to work right, without a understanding of what 20 foot pounds feels like. Before heading off to the park with Danielle, I decided to take my new (and admittedly cheap) Michigan Industrial Tools torque wrench and check the torque on the bolts on my hitch.

I set the wrench for 20 foot pounds, put it on the bolt, and pushed. Since the torque wrench is supposed to click when it reaches the amount of torque specified, and I didn’t hear any click, I figured it had to be tighter, so I pushed a bit more. The bolt turned, then I pushed a bit more. Suddenly there was a BANG and the bolt clattered to the ground having broken off.

Later in the evening I hooked the torque wrench to another wrench and tried it out, applying force every way I could think of, and it wouldn’t click. I played with it a bunch, turned the adjustment all the way in and out a few times, applied more force to it, and after about 20 minutes of playing it finally freed up and started working. I then found out how little force 20 foot pounds actually is.

It took my working the adjustment part of the tool back and forth a few times, and then applying a solid amount of force opposite the direction the torque wrench should be used in (that is, against the arrow) before I felt something loosen up inside the tool and it started working.

So, it turns out that the problem seems to have been caused by my lack of knowledge and the torque wrench’s generally being crap. I’m still torn as to whether or not I should return it. Sure, it only cost ~$30, but if it’s not reliable it’s not particularly useful.

The bigger problem is finding another bolt. What I need is a 3/8-16 u-bolt, for 9/16″ outside diameter pipe, but I can’t seem to find it. Checking both McMaster-Carr and Grainger, all I can find is 1/4-20 parts at that spacing. McMaster-Carr lists the 1/4-20 stainless steel part as having a working load limit of 435 pounds, which is probably 4x or 5x what the bikes and hitch weigh. I’m not sure if it’s enough, but it might be my only choice.

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