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I finally had a post hole digger shear a pin on a rocky slope in Asheville
Was setting a line of cedar posts on a steep backyard job last Tuesday when the auger hit a hidden granite shelf. The shear pin snapped with a loud crack, and the whole unit started to twist. I had to shut it down fast and ended up hand-digging the last two feet with a rock bar, which added about 3 hours to the day. Has anyone found a better shear pin setup or a different method for really rocky ground like that?
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diana5121mo ago
Respectfully, I see it different. That shear pin saved your gearbox and your arm, plain and simple. A granite shelf hidden six inches down is exactly the kind of surprise that rips the whole auger head off if you push through. Hand digging two feet with a rock bar beats a $1,200 gearbox replacement and a trip to the ER any day. The key is planning for that rock bar time instead of fighting it. I'd rather eat the extra three hours on the clock than gamble with a stronger bolt that might not break when it needs to. Sometimes the old way is the cheapest way.
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west.richard3mo ago
Used to think a shear pin was just a cheap part you replace. Then I watched a guy's whole gearbox get wrecked after his "upgraded" bolt didn't break. Saw the metal twist and snap something inside. That pin is there to be the weak link on purpose. Now I just carry a bunch of the right grade bolts from the hardware store and expect to use them. Rocky ground eats equipment.
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My uncle's old tractor manual had a whole page just on shear bolt grades, with a warning in bold about using the wrong ones. It basically said what happened to that guy's gearbox would happen, and it's way more expensive than a 50 cent bolt. I get why @iris927 learned fast with a mower blade, that's a loud and expensive way to find out.
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