How to fix a damaged rear shock bolt

[ManzanoNissan]

Simply put I screwed up. I had a rear shock I was removing, it was stuck on, I used a ball joint removal kit but caught part of the frame where the shock rests against and didn't know it. While I was torquing to remove what I thought was heavily seized, I was at the same time rounding the end of the shock bolt. My bad eye sight didn't see that until it was noticeable that shock was not moving off and I was damaging the bolt end.

I literally rounded the first three threads. I tried filing down the damage so that a nut could go on and maybe there was enough thread to grab from the other side but no luck. I've got four threads at the end shot. I've tried filing down so the bolt is even around. No idea what to do next. Does anyone have experience with what to do after this sort of damage is caused. Is there anything that can be done to save this or does the truck have to have a new bolt welded to the frame?

[ManzanoNissan]

Ok so best I figure so far I need a die and I need to rethread that bolt with the die. That bolt uses a 17mm nut so I'm assuming I need an M10 die?
I'm not sure how I can possibly get that die lined up so perfect that it will cut perfect threads to match the remaining back of the bolt (it's just the first four threads that are gone), should I just die cut that bolt to a smaller size and plan to do the entire bolt front to back?
I'm lost on what the smaller size should be, I don't see nuts for an M9 die and an M8 uses 13mm nuts which I'm thinking is getting to small for torque needed to secure a shock to the frame.

[ManzanoNissan]

Ok I think I got this figured out. I think I need to purchase a split die thread chaser. Again I believe this is an M10 bolt using a 17mm nut, which is a 1.5 thread. So I'll need this little fella. If anyone can confirm I'm on the right track, let me know.
https://www.threadtoolsupply.com/murray ... 0x150.html

[VStar650CL]

I would think the studs are M10, M9 would be an oddball size for Japanese hardware. Probably M10-1.0 (fine) but you should get a thread gauge and not assume, since M10 also comes in an "extra fine" 0.75 pitch. If you can restore the threads with a die then that's the best option. Even if it doesn't line up exactly and staggers the original threads a bit, keep in mind that the nuts don't sustain much load in operation, first because the studs are shouldered and second because the bushings absorb most of whatever side-side force is applied. If it is a fine thread but there isn't enough left to bite, you can probably change to a coarse 1.25 and die cut it all the way down. The coarse thread has a minor diameter about 0.3mm smaller than the fine thread, so even though it won't look pretty, it should give you enough bite to stay put. However you repair it, you should consider using a nylok nut instead of standard so it will stay in place without a lot of torque.

[ManzanoNissan]

I would think the studs are M10, M9 would be an oddball size for Japanese hardware. Probably M10-1.0 (fine) but you should get a thread gauge and not assume, since M10 also comes in an "extra fine" 0.75 pitch. If you can restore the threads with a die then that's the best option. Even if it doesn't line up exactly and staggers the original threads a bit, keep in mind that the nuts don't sustain much load in operation, first because the studs are shouldered and second because the bushings absorb most of whatever side-side force is applied. If it is a fine thread but there isn't enough left to bite, you can probably change to a coarse 1.25 and die cut it all the way down. The coarse thread has a minor diameter about 0.3mm smaller than the fine thread, so even though it won't look pretty, it should give you enough bite to stay put. However you repair it, you should consider using a nylok nut instead of standard so it will stay in place without a lot of torque.

Thanks Vstar. I'm going to buy the M10 split die thread chaser from McMaster. I'll take the nut into Autozone/Oreillys tomorrow and match it on their little bolt and hole match thingy and I'll find the proper thread for that split die. I will pick up a couple nyloks while I do that fact finding. Those split die look pretty handy and being they are an inch wide, finding a fit for a deep socket won't be difficult either.
https://www.mcmaster.com/products/split ... ~1-5-mm-2/

[VStar650CL]

Chasers are good for bunged threads but you may not get it to start on one that's completely messed up. I'd grab a regular tapered die to cut the first few threads, then you can start the chaser without difficulty and run it down the rest of the way.

[ManzanoNissan]

Hey Vstar just confirming your last note. The Chaser is split so I can start it at the middle or bottom of the bolt and back it out to the front of the bolt, the damaged area. This is why I went with the split die as opposed to the regular die.
However, thinking about this all night, I'm going to assume that you would have taken a regular die and recut the threads at the beginning of the bolt because the shock itself only uses those first 6 or 7 threads. (so who cares if the threads won't match up).

If I'm correct in assuming this is how you'd have approached this situation, my question to you would be: What size die would you have used and what was the corresponding sized nut? Let's hypothetical here: Based on what you've written I'll assume the M10 bolt had a 1 thread pitch and you would fix that by using an M10 with a 1.25 pitch? Keeping in mind the first 4 threads are shot, almost not there.

Thanks for letting me gain more of your knowledge. Appreciated!

[VStar650CL]

I'd try to rethread in the original size before resorting to anything else. If you have enough clean thread at the base to line up the split chaser cleanly and back it to the end, that's the right thing. I had the idea more of the threads were bunged than that, but if that's wrong, definitely try chasing it from base to tip first. If that doesn't work or leaves too little bite, then go for an alternative.

[ManzanoNissan]

I'd try to rethread in the original size before resorting to anything else. If you have enough clean thread at the base to line up the split chaser cleanly and back it to the end, that's the right thing. I had the idea more of the threads were bunged than that, but if that's wrong, definitely try chasing it from base to tip first. If that doesn't work or leaves too little bite, then go for an alternative.

Gotcha. Just back from Autozone and I wasn't close. It's an M12 1.25