Sunday, May 13, 2012

Cotter Pin Replacements

This sort of thing appalls me.

Pictured is the end of a bucket pivot pin on a Bobcat backhoe. That may be the lamest cotter pin replacement I've ever seen in my life. (The backhoe is in my backyard for a retaining wall job.)

That big pin wants a 7/16" diameter cotter pin through it. I have an assortment of pretty big cotter pins on hand, but no cotter pins that big.

The best I can do here for a proper replacement is a 3/8" diameter bolt, with a nylock nut on it. Here's a view of that fix.

As ersatz cotter pin replacements go, that's a pretty good one. It sure beats a length of insulated copper wire. Here's a more contextual view.

I'll leave the other 'cotter pin' be. At least it has some substance to it.

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Cotter pins are a favourite hardware item of mine. Any machine with a cotter pin in it somewhere is ok by me. Any machine with a cotter pin in it is likely to be accessible; by 'accessible' I mean comprehensible to a human being of normal faculties and intelligence -- accessible without several kilobucks worth of microprocessors and software.

The laptop computer I'm writing this on has no cotter pins in it. Its workings are inaccessible to me. At the same time that it connects me to the world with this fabulous blogging software, it alienates me -- it renders me powerless to set it right should it go wrong. Should my laptop computer fail on me, I sure as hell won't be able to fix it with a cotter pin.

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Anyway, Machinery's Handbook (21st edition) has a nice summary of fractional inch cotter pin specs on page 1114. Here's a photo of the table.

I hope that doesn't get me arrested for copyright infringement.

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By the way, the name 'Cotter' is from Dr. Rudolph Cotter, who introduced the pin to the world in 1834.

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