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Bolts & Nuts

Oct 11th, 2013 | By | Category: Jack Schrock's Blog

Jack SchrockThere is a lot of truth to the notion that the weakest link determines the strength of the chain. And so it goes with wrecker hardware, especially mounting hardware because there really is the good, bad and ugly to choose from.

To explain further, attachment hardware comes in degrees of “hardness” from almost soft to hard and brittle. And both extremes have good and bad features.

The real soft stuff is readily available and comparatively cheap. The next level is neither so cheap nor readily available and some installers prefer this level of quality because the mounting bolt will s-t-r-e-t-c-h before it finally breaks. This is a good feature because the bolt will keep all the pieces together throughout the winching process. And after a hard pull, most towers will check the torque of the mounting bolts on their HD wrecker, often finding them loose.

Now, at the other end of the scale are the extremely hard bolts and there is a testing scale to establish just how “hard” they are. In my experience, Grade 8 is about the hardest that is readily available. The good news is that it does not stretch like its softer cousins. The bad new is that it does not stretch like its softer cousins. Yes, something this hard will completely break when it passes the failure point which means that, in a hard pull, those super hard bolts can break with the sound of a rifle shot … Oh yes, and pieces can fly around just to keep you on your toes (or is it “tows”)?

Breaking mounting bolts is not a good thing so most installers and manufacturers avoid using such super hard hardware in HD wrecker applications. Now please understand that my point of reference here is a Holmes 750 or 850, which would pull until something “broke” as I’ve seen wrecker masts crash down when that happens. In today’s world, I question whether any of the fixed boom hydraulics develop enough winching power to break mounting bolts. Tom Luciano of Miller Industries would know best as he’s worked both mechanicals and hydraulics.

Oh yes, always use a torque wrench unless you’re like my friend Mike Stenger. Big Mike would say “tighten her up til’ she strips and then back off a ¼ turn.”