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Snapped a post auger bit on a rocky job site last Wednesday
I was setting posts for a deck fence in Boulder County and hit a buried boulder about 18 inches down, which twisted my bit right off the drive shaft. The whole auger head sheared clean off and I spent 2 hours digging that rock out with a pry bar. Has anyone here had luck drilling pilot holes with a smaller bit before going in with the big auger?
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lunag304mo ago
Oh man, that's a bummer of a break... but honestly, I think pilot holes are a waste of time in rocky soil. You're just asking for the smaller bit to get stuck or snap too, and then you've doubled your headache. The real trick is to go slow and steady with the big auger, let it chew through whatever comes its way, even if it takes a few extra passes. If you hit something solid, back it out and try a different angle instead of forcing it through... that's how you keep the bit from shearing off in the first place.
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milacraig4mo ago
My friend Dave snapped three pilot bits in one afternoon doing that, then just grabbed the big auger and finished in ten minutes.
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grace894mo ago
Whoa, that's a really good point actually! I heard from some old timer at the hardware store that pilot holes in rocky soil just make things worse because the small bit can't handle the shifting rocks and it jams up. @lunag30, what you said about letting the big auger chew through and backing out when you hit a snag makes total sense, I've seen guys snap bits that way trying to force it. Honestly, gambling with a smaller bit first just adds another potential fail point.
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