Options if that should fail depend on if/how hard it is but I suspect if hardened much, it might be easier to plug it with an unhardened cylinder and tap that rather than try to tap it directly. I'll grab a normal cut tap and see if I can either get it started or drill/bore out the first few damaged ones (thanks for that suggestion) and then run it in. Thanks for the info on the roll tap (aka form tap). It's also worth mentioning that these threads don't seem to be either load or torque bearing, the splines take the torque and the CSK head screws (and CSK 'washer' I'll have to make) really act to pull the crank arms on and retain them. Although it's in a state currently, the friend wanting fixed is good at the bodywork and painting side of it. Hence the reason for not simply replacing it and also my preference to not go for the nuclear option if possible and keep the original thread.ĭeeper may definitely be an option if, as has been suggested, it isn't hardened. Mattthemuppet has hit the nail on the head that it's a fancy vintage BMX axle - and I'm probably wrong in using the term "axle" here as it's probably technically a shaft (I'm not the one with the bike fetish here.in case you couldn't tell!) that goes between the pedal crank arms. The thought it might need differentiating from a motor bike part never occurred to me. But I THINK I'm pretty safe on the MOTORcycle connection and the idea of it being off a Brit or Yankee made vintage bike.Īh, sorry guys. How deep do the messed up M10 threads extend? If it fits well enough how about just sigh and use an M10 bolt? The damage is done already.Īnd of course I jumped to all the same conclusions that Arcane suggested and I waved at in agreement. That should ensure that it doesn't strip out the obviously damaged threads.Īnd last of all. And at that point and assuming you manage to get a bottoming tap to run clear to the end of the hole tell your buddy to get a bolt that is longer and cut and file until it just barely seats the axle like 1 turn before the bolt bottoms. And since an M10 isn't far off the target the first few threads SHOULD aim the 3/8 tap in the right direction since the original 3/8 threads would have done the same for the M10 tap or bolt that did the damage. Next would be to clean up the threads with the proper 3/8-24 tap. Perhaps get back to him and convince him. For any solution that requires removing metal it's the least intrusive. Not sure why your buddy dismissed this idea. Next up for least damaging would be your original idea of a Helicoil. If your buddy is worried about a Helicoil removing metal I can't see him liking this plug idea. And if it's even too close to the end of the support and depending on what the motorcycle is used for and how hard it is ridden there's still a chance that it could shear at the end of the bored out hole for your plug if it's too close to the end of the support from the fork leg clamping. I would suggest that it not even be as long as the clamped and supported area of the fork leg it fits. The plug you add would never be part of the load bearing part of the axle so keep it small and don't go overly deep. I'd be very careful if you choose to bore out and press in or "glue" in a new insert. Using a form threading tap on metal which has a spring temper and will fight the forming should be. They would simply not stand up to much punishment otherwise. I don't know about your 4140 assessment but certainly any and all bicycle and motorcycle axles are heat treated. Not sure why there's a spline but odder things have been seen before. And the spline you mentioned and the single seating screw at the one end suggests it slides into a front fork and is then clamped by the fork legs. And only newer metric bicycles use tubular thinner wall through axles on some applications. I don't know of any older bicycles that used anything near to that size for an axle. I'm waving in agreement with Arcane here.ģ/4" and inch size thread suggests an older vintage MOTORcycle of some sort.
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