Broken M6 bolt in OTK Sprocket Hub

So I messed up…lol. I was tightening down the sprocket hub pinch bolts after aligning my sprocket with a new clutch and one of the bolts snapped in half. It wasn’t even when I was torquing down on it, maybe 60% of the way tight and then it just broke free. The bottom half of the bolt is stuck in the lower threaded portion of the hub.

What is the best method to extract this? I’m thinking a screw extractor set could work. I have access to the bottom of the bolt from the underside of the hub. I think I could drill into the bolt and then tap a left hand thread extractor into it and hopefully twist it out. I sprayed it down with PB blaster so it can soak overnight. Is this right method? Help would be appreciated!

If that is just a cap that you can remove I would disassemble the hub so you can get a good straight shot at it. Also, use a center punch to get a good starting point for the drill bit. Use a new drill bit as well. An easy out should be able to remove it unless it is seized in there.

If the top part is the hub can’t be removed because it is a crush type collar, and is one piece, it becomes more difficult for sure.

1 Like

Lock the brake rotor so the axle can’t spin. You’re going to have to try a bolt extractor or drill it out. Might get lucky when drilling it out and the drill bit grabs and spins it out the other side.

If you have access to the end of the bolt like you said then use a sharp drill bit and go slow trying to grab the metal and spin it out the top of the hole. Soak it in a good penetrating oil first, maybe even a touch of heat. Recommend using anti-seize when reassembling with new bolt.

Ricky’s way should work, but if the two sections are not completely aligned, you might run into friction. What Clayton said - If that bolt hole goes all the way through, you should be able to screw it all the way out “righty-tighty”, rather than trying to back it out. If the threads are clean it should come out easy as there is no tightening tension (the top half is not threaded and depends on the bolt head to pull it tight). Just start with a small drill bit and go slowly. Use a spray lube on the underside threads and make sure the threads are free of gunk. You’ll have drill to use an easy-out if it doesn’t work anyway, but do the best to give it a chance to go out the other way.

For the future, replace the bolts in the hubs and carriers on some regular basis. We had a light schedule and replaced bolts at the beginning of the season. Good luck.

Thanks for the tips! What is odd about this is that it broke while tightening, not while loosening. So I don’t think it is seized in there as I was able to loosen it off to adjust the alignment.

The top part can’t come off as it is all one piece. But the top part is not threaded which is good. I don’t think it is seized as I was able to loosen it up to adjust the alignment and it broke on tightening. It is just in the lower half which is threaded so it should not be under too much tension either.

I think I am going to try to drill it from the top and hopefully it just screws all the way out. If not, I will use a screw extractor to get it out from the bottom.

1 Like

Good luck, let us know how you make out with after pics. Be careful drilling as there is a lip on for the head of the fastener and you don’t want to remove any of the material. I am sure you already know that but just in case…

Broken bolt update! I was able to use a punch to create a depression in the end of the bolt from the bottom. I then used a cobalt drill bit to drill into it from the bottom. I was just intending to start a hole for the bolt extractor kit but to my surprise, the bolt started backing out with just the drill bit biting into it! Took my time to make sure I was not hitting any of the hub or jaming it further. It came right out no problem! Soaking it in PB blaster last night worked a treat!

Thanks for the help everyone!