Stuck bolts, rivnut and crank

[focomat 1c]

An update on my earlier suggestion ........... The flanged head of a rivnut is 0.98mm thick

A hacksaw blade ( Starrett ) is 0.92mm thick , so it will fit in the available space . However

it would be best to blunt both sides of the hacksaw teeth with a Dremel or similar , to

avoid damage to the frame and cable guide

 

[Splatter Paint]

Crank bolt is 8mm head? Can you file a 10mm down and hammer that in? I have spline drive bits that you could try but no Torx.

 

[The History Man]

I’ve done this recently. If you want to save the cable guide it will take a little longer.

Grind or cut off bolt head to remove guide.

Then once guide remove grind bolt down to rivnut flange but no further. Use long nosed pliers or long nosed mole grips to grab soft rivnut flange crushing it into a cup around the bolt stump. Grind off cup and repeat cup making process. Eventually the bolt drops into the frame.

My Dynatech is testament to my success using this method without damaging frame. I I used needle nosed mole grips and a Dremel.

 

[ishaw]

I've got the rivnut out, managed to get a saw blade between the frame and the spinning nut and it made its way through it. Need to get the remains out, but I can't untill I get the BB out, and hope the down tube hole is big enough....

I started to drill a hole in the crank bolt in preparation for using an easy out, but I stopped as I suddenly remembered that the crank bolt is hollow. Would the easy out still work with a hollow bolt?

I've also tried cutting a notch in the bolt but as it is recessed below the crank arm, I can't get anything in there.

The only other option I can think of is to get something welded onto the bolt which can then be used to unscrew it, but I've no access to such things.

Any other bright ideas I can try?

 

[TOMAS]

Depending what crank extractor tool you have - you could take a 9 or 10mm drill and drill the head of the bolt off - drill straight down into where the hex key goes.... - once the head has gone, pull the crank off with the puller - you'll then need to cut a slot into the stub of the remaining bolt and wind it out with a suitable flatblade. One tip - not sure what hex keys you use but Wera are THE best i've ever come across and their design greatly reduces rounding of hex heads.

*** EDIT ***

Trying to remember - are XTR M952 BB's running M8 bolts like the lower models or M10 - i'm thinking M10 actually?? If this is the case you'll need a larger drill bit - 11mm/12mm. Again cut a slot into the stub of the hollow bolt after and wind it using a very wide flatblade OR perhaps the actual saw blade (however they care very brittle)...

 

[ishaw]

Thanks, I have a lovely set of wera Allen and tirx keys, I wish the previous owner of the bike had some though, trying to right their wrong.

I might try the easy out route, got nothing to lose. If it fails I can drill out the top of the bolt and at least get the crank arm off and they try to get the remnants of the bolt out of the BB.

If I had a large torx key if try that too, bit I've nothing big enough.