Removing snapped Al derailleur hanger

[iwantanewbike]

Derailleur hanger snapped and could only remove one of the two 2mm hex mounting bolts. The other one is seized and its head is rounded. Any ideas? I've tried the following:

- penetrating oil
- using a Dremel to cut a slit in the bolt on the other side of it and attempted to turn it clockwise with a flat head screwdriver
- drilling 2mm holes around the bolt in the hope that I could get the remaining hanger off and out of the way so that I could hopefully get purchase on the bolt with grips and turn it clockwise. This is painstaking and not sure that it will work due to the shape of the drill bit and the amount of contiguous aluminium that would be left.

As the head of the bolt is on the inside of the frame's rear triangle it will be difficult to drill it through in that direction e.g. to prepare to use a mini easy bolt extractor or drill through completely - I can't use a bolt extractor on the other side (outside of the frame triangle) as they are intended to turn anti clockwise.

Should I take it to a pro?

 

[wonderloaf]

You could try hammering a torx driver bit into the rounded hex recess, this has worked for me in the past. If you can grind a bit of the end of the torx bit to make the splines nice and sharp that might help as well.
Good luck 🤞

 

[Cycleops]

If the foregoing doesn't work your only option will be to drill it out. I don't think it warrants your wish for a new bike just yet.

 

[I like Skol]

Drill the head off the bolt then the remaining stub will come away with the broken hanger. Easy peasy

 

[faster]

Drill the head off the bolt then the remaining stub will come away with the broken hanger. Easy peasy

As said in the original post, it's on the inside of the frame so the op would be hampered by the chain/seat stay on the other side.

It should be pretty easy to drill down the bolt from the outside, although from the photos it looks like you've already had a go. I'd try again, as this is your best option. You'll just need a good punch to get it started and a good drill bit.

You may even find the bolt starts to wind out while you're drilling.

 

[I like Skol]

I'd still go for drilling the bolt head off because once off you are home and dry. Doesn't need drilling straight as you will not be anywhere near the frame. Presumably an M5 or M6 bolt so drill with a bit of +1 or +2mm and the head should just pop off.

No need for an easyout or similar, once the head is gone it will fall off.

 

[Big John]

https://www.screwfix.com/p/bolt-extractor-set-5-pieces/1112v

 

[iwantanewbike]

Ok, so I think drilling the head off as suggested will be fine. Initially I thought both the frame and the hanger had a thread tapped, however I've just run a probe in the other (empty) bolt hole and confirm there's no thread in the frame. So drilling the head off will mean the hanger and bolt will just fall out. Saying that, I'm so far through the aluminium with the Dremel now that drilling the last bit of the bolt from the aluminium hanger on the other side will work equally as well should it be too awkward to drill the bolt head from the inside of the frame triangle.

 

[iwantanewbike]

OK it's off now after a fair bit of Dremel action and a cutting disc, which was much more effective than drill bits. Now to avoid snapping the next derailleur hanger with the DAG tool!