My shimano slx crank arm has to Allen key bolts holding it on, one undid quickly the other was very stiff and unfortunately rounded out. Any thoughts from the collective?

Wedge a flat screw driver or a torx in there? Or take a hacksaw to it and cut a slot in the head

Re tighten the good bolt to release pressure on the one you broke and use somthing else to wedge in it.
Or get an easy out and use that but its a bit of a pain to drill hole in a small bolt like that

Tried a torx and a flat head but too tight, too low to cut a slot in it, but like the idea of tightening the other – good idea. Have thought of easy out but it is a small bolt made out of plasticine metal.

Drill it out

Right, up date! And thank you for ideas above.
Tried tweaking the other right up and epoxy gluing in the Allen key in round one – no joy
Tried hammering in a torx bit – no joy
So next was the extractor, drilled down the bolt, head might be soft but shaft took out two bits, bored out extractor hole, screwed in extractor, tightened up then shaft sheared.
So now have an extractor shaft stuck in the bolt, the mole grips we have here just slip on them, even when seriously over tightened, have tried filing flats on the shaft but this is very hard metal that appears to polish the files!

Ideas at the mo are get some files for hardened metals and bigger mole grips. Any ideas much appreciated.
Thanks Rich

Any chance of a photo of what you’ve got now?

Hand-held vice and rotate that?

A couple of suggestions if you still have some extractor to grapple. Soak the offending area in Plus Gas for a while available from motor factors and the like. Then try again or apply heat with a blow torch. This heat application will do the job but may cause discolouration. If you can’t get hold of the extractor you are probably going to have to drill through from the other side and knock the extractor back out, then drill the bolt out completely.
There was an slx crank on the classifieds for £30 the other day 😉

Mine did the same. I carefully hack sawed through the bolt by poisitioning the crank so I could get a junior hack saw blade down the slot. . It turned out I only needed to get about 2/3rds of the way through before it gave enough to be turned by a flat bladed screw driver.

How do you get the threaded bit out after that?

Try sawing through as above or maybe drill the bolt shaft from the other end?
That way you can get an extractor shaft stuck in both ends,pics of that please 🙂

Friend of mine has run a Saint set for years with one bolt. Just sayin’.

>.< Wrong thread

Great replies! Keep them coming….

Not too helpful but I sheared the head off a HT2 bolt and the LBS managed to get it out for a few quid. I would much rather not see the bodging that had to go in to getting it out!

Update time.
Bought, ‘freeze your nuts off’ , a new ‘super’ penetrating oil, new vice grips (big ones) and a diamond file.
Then filed the stuck extractor shaft to put two flats on it, sprayed bolt with super penetrating oil, left it, sprayed with the freeze, put new vice grips on and turned extractor – hoping it would undo bolt and all – extractor sheared but this time as a jagged mess too low to get grips on! : (
Thought about it, was getting ready to saw through the axle, taking out the whole chain set and one side of bearings. Teenage son talked me around to give it another chance. Have now bought more drill bits, more extractors and going to have ago from the other end but have metal saw handy (and eye on the slx cranks on here) to cut the bastard off!

Keep the other bolt in tightened up.
Try tapping around the crank with a mallet a few times then penetrating oil. Also hammer the bolt from both ends with a screwdriver or similar.Even if it doesn’t loosen it up it will make you feel better.My mate tried everything and didn’t want to damage his XT crankset.
Got his dad to do it in the end by drilling through the bolt till it shattered bit by bit-Wear goggles!
Good luck and persevere.

If it comes to it I would imagine you can saw only the left hand side off?

How much have you spent on shit to get this sorted so far? Do the cranks NEED changed or is it just a bike tart thing?

How much have you spent on shit to get this sorted so far? Do the cranks NEED changed or is it just a bike tart thing?

I’d be getting a dremel cutting disk down the slot in the crank arm and cutting the bolt there. At least then you can work on the crank and no other damage is done. The preload will then be off the bolt so if not seized may twiddle out with an easy out quite easily…

The daily update! James has pointed out tool expenditure and certainly time invested is close or exceeding the cost of cranks. Position we are in now, rounded-out (back) crank pinch bolt stuck in with extractor stuck in it, sheared off level with the bottom of the allen head. Have now drilled a hole throught the bolt from the bottom to the extractor, the drill will not touch it and it won’t punch out. Have been tempted to drill out the bolt completely (taking out the threads the bolt tie into) from underneath and then either helicoil /time sert new threads for a new pinch bolt. There was no way to grip the head, so some filing in side the Allen head to try reproduce some edges and then finding a tight Allen key and have epoxied this in. I am going to leave it to cure overnight, then plus gas, hammering etc and have ago in the morning.

Has to come off as I experimented with a chain device (i was more jumpy a year or two ago, want to keep my wheels on the ground now) but it upsets the chainline in top x3 gears badly. Needs to come off and get the chain sorted.

Thanks for all of the replies, some really useful approaches here.