Allen bolt snapped in thread

[shouldbeinbed]

Bugger. Refitting a rear rack and the Allen bolt head has sheared, leaving the body inside the frame & not protruding at either end so I can't get a hacksaw onto it to put a notch into it to screw it out.

Do I drill it and find someone to rethread the hole?

help

 

[Smurfy]

What's the frame material?

 

[mrandmrspoves]

Drill.a small hole and try a screw extractor. They're cheap to buy. Basically it has a reverse thread so when it has been screwed in tight it will start to unscrew the damaged bolt. That's the theory anyway.......

 

[cyberknight]

I had the same issue with the bolt stickign about 2 mm out of the frame but to soft to get anything on it, ended up with a seat post rack which is a pain so i might get a screw extractor .

 

[oldroadman]

Drill.a small hole and try a screw extractor. They're cheap to buy. Basically it has a reverse thread so when it has been screwed in tight it will start to unscrew the damaged bolt. That's the theory anyway.......

Used correctly this should work. Stick a bit of Plus gas down the threads first, drill a pilot hole dead centre, use the screw extractor as described (it's reverse thread), job done.

 

[simon the viking]

Drill.a small hole and try a screw extractor. They're cheap to buy. Basically it has a reverse thread so when it has been screwed in tight it will start to unscrew the damaged bolt. That's the theory anyway.......

Yep..... that's the theory.... the reality when I've used them is that you have to use a drill that's so thin that is get hot and welds itself into the hole its drilled, snaps off then you have to drill out a broken hardened drill bit with a slightly bigger drill.... that then goes blunt itself because its drilling a substance harder than itself because the broken one is heat hardened......................................OR the drill goes off at a tangent and comes out the side of the item you trying to remove the thread from.......

Perhaps it's just because I'm a cack-handed bodger though

 

[Smurfy]

If you're lucky, the drill will pick up on the bolt, then screw the bolt out forwards under drill power.

In my experience, screw extractors don't work very well in small sizes. They are quite hard and brittle to enable the extractor to bite into the screw. Unfortunately that means that they snap off quite easily in use.

I'm wondering how the bolt lost its socket head. If it's cross threaded then it'll be a real battle to get it out again.

 

[shouldbeinbed]

cheers all, @YellowTim, its an Aluminum frame and I am concerned it might have caught a crossed thread, I cant figure why it would just go otherwise but I didn't feel it.

Thinking on it, I may well let my LBS have a go at it, I'm too cack handed for such a precision job with powertools and if I get it wrong then no proper mudguard or rack anymore and its my urban utility bike so would be quite a setback.

 

[Tim Hall]

The application of SCIENCE and household chemicals can dissolve the steel bolt, leaving the aluminium frame untouched. @zigzag did this with stunning success.

 

[Smurfy]

cheers all, @YellowTim, its an Aluminum frame and I am concerned it might have caught a crossed thread, I cant figure why it would just go otherwise but I didn't feel it.

Thinking on it, I may well let my LBS have a go at it, I'm too cack handed for such a precision job with powertools and if I get it wrong then no proper mudguard or rack anymore and its my urban utility bike so would be quite a setback.

That's why my first question was frame material, as aluminium cross threads and damages much easier than steel.

Is it drive side? If not there will probably be space to put a nut on the back. Unfortunately on the drive side the chain runs so close a normal hex nut is often not possible. However, you may be able to drill it slightly large and fit a sleeve nut instead.

 

[shouldbeinbed]

That's why my first question was frame material, as aluminium cross threads and damages much easier than steel.

Is it drive side? If not there will probably be space to put a nut on the back. Unfortunately on the drive side the chain runs so close a normal hex nut is often not possible. However, you may be able to drill it slightly large and fit a sleeve nut instead.

It's non drive side but the disc rotor runs close to the exit of the hole, I'll have a look tomorrow and see if I could fit a nut in there without it catching.

 

[Lanzecki]

Use a small drill bit to drill down the center of the bolt. With any luck the bolt will start to move with the drill bit and rorate out the other side of the frame. Coat it in your preferred lube though.......

 

[classic33]

Keep some oil in a small container, bottle lid, and keep on dipping the drill bit into on a regular basis whilst drilling.

 

[classic33]

Keep some oil in a small container, bottle lid, and keep on dipping the drill bit into on a regular basis whilst drilling.

 

[Lanzecki]

Keep some oil in a small container, bottle lid, and keep on dipping the drill bit into on a regular basis whilst drilling.

That's what he said!