Method of fixing damaged threads on rear shock lower mount
#1
Method of fixing damaged threads on rear shock lower mount
I cross threaded a lower shock mount bolt. They are coarse M14x2 and go in at a slight angle which makes them super easy to cross thread especially when you're trying to get everything lined up. Even with clean threads and hand tools I managed to bung up the first thread and a half in the nut that is part of the frame. From the backside there isn't enough room to get a tool, bolt, or wrench up in there.
I ended making a 'tool' from a grade 10.8 bolt to come in from the back of the threaded hole to un-frig the threads. Basically I cut the head off a bolt, machined an 8mm hex head, and ground a screwdriver slot. It could certainly be done with just a grinder or cutoff tool and a some patience.
Photo Attached.
The slot is so it could be started with a screwdriver until the hex head protruded enough to accept a socket. Lots of oil was used to prevent galling during thread correction and to reduce torque so the little hex head wouldn't break off. It went through very well and didn't require any concerning amounts of force..
Now I realize that the damaged threads aren't 'fixed' but rather just re-aligned to not interfere. I decided that the remaining good threads were suitable for the job to get me back on the road. This is an assessment that anyone else will have to make given their situation and safety so do it at your own risk.
I saw that someone else fixed one of these by drilling it out and using a thread repair/insert kit. That's probably a better method if you can find one quick enough. The stores around here only had them up to M12 size.
Just sharing in case this can help someone out of a pickle.
I ended making a 'tool' from a grade 10.8 bolt to come in from the back of the threaded hole to un-frig the threads. Basically I cut the head off a bolt, machined an 8mm hex head, and ground a screwdriver slot. It could certainly be done with just a grinder or cutoff tool and a some patience.
Photo Attached.
The slot is so it could be started with a screwdriver until the hex head protruded enough to accept a socket. Lots of oil was used to prevent galling during thread correction and to reduce torque so the little hex head wouldn't break off. It went through very well and didn't require any concerning amounts of force..
Now I realize that the damaged threads aren't 'fixed' but rather just re-aligned to not interfere. I decided that the remaining good threads were suitable for the job to get me back on the road. This is an assessment that anyone else will have to make given their situation and safety so do it at your own risk.
I saw that someone else fixed one of these by drilling it out and using a thread repair/insert kit. That's probably a better method if you can find one quick enough. The stores around here only had them up to M12 size.
Just sharing in case this can help someone out of a pickle.
#4
The majority of the threads were intact. It torqued fine, didn't baby it. Of course I'll be keeping an eye on it for a while but ultimately if I felt it was a sketchy fix I wouldn't run it.
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