[Driverfound337]

Anyone seen this on their Shimano's? I have been on these for two years and went to change the chain ring for the first time, started to loosen and then it fell off. Hate to toss a crank but I can't run a ring on 3 bolts comfortably. Not the end of the world but didn't expect this from my shimano
IMG_3074 by driverfound337, on Flickr

 

[BadgerOne]

Looks like a perfect case for a screw extractor kit. That said, either the threads in the spider are knackered or that's just cast-off stripping from the removed bolt. Hope it is the latter, because if it is the former you may have to buy a new crank anyway.

 

[eshew]

Seams like there would be a few different ways to fix that. Doubt you'd need to ditch that crank... But anyway, fist things first, get that piece out. Lube it up & Get an extractor.

 

[bcriverjunky]

Drill and tap.

 

[Driverfound337]

I’ll give it a go!

 

[Mountainfrog]

Fixable.

 

[bayposter]

Drill and tap.

Those chainring bolts already have their center drilled out. So no need to even drill!

A little liquid wrench overnight and a tap should do the trick.

 

[wschruba]

Those chainring bolts already have their center drilled out. So no need to even drill!

A little liquid wrench overnight and a tap should do the trick.

The hole is 3mm/thereabouts, I believe. It would be prudent to enlarge it a bit for a larger size spiral extractor, since the small ones are not great for having force put through them...then you'll have a stuck stub AND a broken piece of tool steel in the crank arm.

You can buy single packs of drill bit/extractor combos made by Hansen (Irwin/some other re-brand) at many auto parts store in the United States. Just remember that the drill bit is sized for ~1/3-1/2 way up the extractor, not the tip.

While you're there, pick up a can of CRC freeze-off. Since it looks like corrosion sitting in that hole, it would be a good idea to try to use differential expansion to help you out here. Both parts are aluminum, but it may still help--and it's a good penetrating lubricant, to boot. Wear thick nitrile gloves when spraying--it gets COLD.

 

[bayposter]

The hole is 3mm/thereabouts, I believe. It would be prudent to enlarge it a bit for a larger size spiral extractor, since the small ones are not great for having force put through them...then you'll have a stuck stub AND a broken piece of tool steel in the crank arm.

That's a good point. And the pre-drilled center of the bolt certainly makes a nice pilot hole.