Broken Rear Sprocket Bolt

[wherearewe]

So i finally came to re-assemble my rear hub. All new brake components, powder coat, chain and sprockets etc.
However when i was chasing the threads on the hub before fitting the new sprocket, i discovered one of the bolts has sheared off about half way down. I guess there is about 10mm of bolt left in the hub. I didnt even notice when i was removing them. Looking at the original bolt (which i kept) it looks like it has been like that for some time. They look a little corroded but not shocking bad.

My question is what should i do? Penetrating oil and an easy out? Im vaguely scared of breaking an easy out inside the hub, and it looks pretty well settled down there. Cut down one of my new bolts so 1 bolt is shorter or refit the old one? Def seems a bit sketchy but i dont think it would do too much harm. Still has 15mm of thread or so plus lock tabs. Take it too a machine shop and let a pro deal to it?

Opinions or tips?

Thanks in advance

 

[Signal]

If the bike has done a lot of k's with the sheared bolt it might not be a huge issue and as you point out the lock tab should stop it coming out. The bolt will experience more shear force from the sprocket than axial loading.
Some blue medium strength retaining compound might soothe your mind as well. I would probably cut a bolt down or tidy up the end of the original, it's not ideal but probably ok.

If you are dead set on removing it a broken off easy out is a show stopper and I would not use one.

Both my ideas for removing it involve a lot of mucking about.
Do you have a way to accurately centre the hole for drilling e.g. a mill or even a drill press? Are the bolt holes through or blind?

Blind hole: It should be possible to carefully drill the bolt out. You would have to spot face the broken bolt first so that the drill bit had a flat starting surface. You could then run a 10mm tap down. If it all goes wrong you can fit a helicoil.

Through hole: from the back side you could drill and tap a 6 or 8mm thread. Screw a bolt (long enough to go right through) in and hit the bolt you screwed in with the arc welder. The heat from the welder loosens the stuck bolt and you could wind it back through the hole it went in. Using a welder to remove stuck bolts does work.

 

[I am Carbon]

If it was mine I would use some penetrating oil, And use a extractor.
Even if it's left in I'm sure it will be okay. the pressure is not so much trying to pull the bolts out as pull the bolts laterally. And in that respect the bolt s almost as strong as it was.

 

[gggGary]

Is it a spoke hub or mag drum or disk?
The spoke hub sprocket bolt holes go all the way through into the brake drum area the mags don't (the ones I have seen)
If the hole goes through, then;
#1 get some rust buster in the hole.
Get a collar to act act as a centering sleeve for a drill bit. a bit of soft copper tubing would be fine for this. or you can probably find a steel sae size sleeve in the local hardware assortment that will fit "good enough" to use as a centering sleeve. This is probably the most important thing; keeping the drill centered. I will guess you have a mag wheel. If so buy a LEFT HAND drill bit, the local auto store has them in several sizes. The idea here is as you drill (which will heat the bolt end) there's a pretty good chance the chunk of bolt will thread out of the hole with the drill bit. Worth a try.
If it's not a blind hole I would increase the drill size until just the thread of the old bolt is left then chase the remains out with a tap. If it's a blind hole I think I'd quit and use a new short bolt.
Whether or not you get the bolt out you might want to chase threads with a bottoming tap, which you can buy, or cut the taper off a regular tap so it can form/clean threads all the way down.
Gauge your abilities and only DIY this if you are confident you can/will make straight holes/ threads. If that doesn't seem like you, I agree better to use a short(ened) bolt and call it a day.

 

[wherearewe]

Thanks for the good ideas. It is a blind hole. Yes i have a drill press.

I spent quite a while last night pondering it and, although i feel i could get it out with time and effort, i think i will just use the one shorter bolt. Its one of six, still has over half the threads available and the lock tabs. Also like Carbon says, most force is lateral. Ill cautiously run it for a bit a keep a real close eye...

 

[xjwmx]

I had three of these and was able to get one of them with an easy out. I have been going around with two short bolts.

I'm assuming you have a mag wheel, since you can't see the end. However - when I did the wheel bearings, I remember seeing the ends sticking through inside my mags and thinking they could be grabbed with a vice grip. But at that time I didn't know they were broken!

Sooner or later I will get some new wheel bearings and dig back down in there and try it from the inside.

Something else; I had problems with them backing out, in fact one of them tore my chain guard off at the rear. I discovered that the way to keep them from backing out was to bend the locking tab up on three sides instead of one or two. It's possible to do it.