So, we got the 644 all blocked up, a little high but nice, tire guy was removing the wheel bolts and I'm watching what hits the bucket, one with no threads, four fine thread ones, a couple course ones, nother stripped one and one more coarse thread.. Near as I can tell they're all supposed to be 3/4-16 and we've got a few that are hosed. Now, ***, man, really dislike the mechanics that are forced to get a machine back out in the field. is a helicoil a possibility? It'd be a real bitch to weld and redrill all the holes, Well maybe not if we had a drilling template. What an unholy mess, tire guy says they're forbidden from installing a wheel with stripped wheel bolts. I'd almost be happy too, the bolts are 2 inches long and stick out the back 3/4 to an inch. fix the threads and weld a nut on the back side. use a bolt to index it up. What would you do!
The early model used studs, you might bring one in, see if it might solve your problem: Stud - R32348 shows to take a 3/4" fine thread nutski. Or fire up the mag drill and whistle while you work. BTW, I hate helicoils on anything other than cylinder blocks and heads, the solid inserts with the drive down locks work well for me though.
Could you drill them a slight bit bigger and re-thread to 20mm? Just a thought.
why not just get a longer bolt and run a nut on the backside if the flange is flat its not like you need to take the wheels off very much that holding a wrench would be a big deal
I had thought about the jump up to metric, not sure how much play there is in the wheel holes. Timeserts threaded inserts are a little pricey but everything in large sizes seems to follow that path, cheaper than machine shop rates.
I was pondering the metric side, 20mm might be close enough of the threads aren't screwed past the root, we do have a mag drill available so even if the wheel holes needed to be bored larger. I was thinking about the inserts too, and if the threads are too dickered, spin a bolt through, run a nut on the back side and weld it to the hub flange, but I'd want to do all the bolts at that point.
3/4 is 19 mm so you would only be drilling .5mm out of the hole sides and most of the old 3/4 thread would remain. Next standard Metric size up is 24mm. I have seen many stripped out threads in haul truck hubs plug welded and redrilled and tapped. Not sure if that is an option in this case.
I have had good luck in many places with the Heli-coils but would be very hesitant to use them on this application where the bolt will be getting rusty and then removed with air wrench. One thought I have is in place of welding and re-drilling would be to skip the welding step and just drill new holes between the damaged ones. Problem I see with the welding is it may have hard spots and/or voids both making it tough to get a good thread. Nice "virgin" material should drill and tap much better. I'd also consider making a jig of some kind to pilot the drill using the first hole as a locator for the next hole. Just be very careful laying it out and work your way around the hub. Another option to look into would be if there is a press in stud available from some other application that you could just drill out the threads and press in then use lug nuts to attach the wheels. Just a quick search found this: https://www.napaonline.com/napa/en/p/NDP6413181/ or this: https://www.peterbiltparts.com/wheels-hubs/hubs/hub-assemblies/we5983r?gclid=CMWSjpqQ2s4CFUMkhgod71gP9A
No hard spots if you oversize the hole before welding and use a suitable wire to plug the holes. Its a very common and successful repair on Cat haul truck hubs here. As I said previously its not necessarily suitable for this job. Some pics would help.
I'll try and get some pics today, Opted to go with the time-sert style, they use the same setup as a helicoil with a slightly bigger hole. Thread a sleeve into the hole and then the sleeve gets expanded into the newly cut threads, giving the correct thread on the inside. I'm planning on adding some red loctite tothe sleeves to make sure they stay put, we have fire available if they need to be removed. What a lovely mess!! Will be attempting to remove the axle today and get prepared to tackle the brakes.