Luke52

As the title suggests, the bolt while holds my derailleur hanger to my frame is stripped; i.e. rounded off, so a hex wrench no longer can turn it.

The wrench slipped while I was tightening it, then continued to slip as I tried to un-do it to replace the bolt.

The bolt is tight, and will hold the hanger on fine, it's more the issue of needing to remove it if need be, for whatever reason.

So now, suggestions on how to remove and replace it, while minimising damage done to the frame?

Thanks,
Luke.

MadBuddha1

vice grips or a tap

trekkie820

There are screw extractors out there that you can chuck into a drill. Basically, it is a reverse threaded, tapered drill bit that digs into the metal of the screw and backs it out. How you would do it would be:

1. Get the proper size (not too big, not too small)
2. put into a drill
3. Reverse the drill so it would loosen a bolt
4. Push down relatively hard, and pull the trigger so the drill SLOWLY spins. If you go to fast, you will have the exctractor machine the head of the screw, rather than dig in.

RonH

+1 on the screw extractor. They're available at any hardware store.

HillRider

Try a brand new hex wrench of the correct size. Hex wrenches, particularly small ones, wear out and get rounded corners and then don't grip the bolt correctly. A new one with sharp corners may work.

dperreno

A large, flat-bladed screwdriver may fit. Tap it in with a hammer. If it's a Craftsman, it will have a square shank and you can use an adjustable wrench to loosen the bolt. Otherwise, you can use a small pipe wrench or vice-grips on the shank, or pliers on the handle. If you use a screw extractor, you'll want to tap it in with a hammer first. Don't use a drill to loosen, just use an adjustable wrench on the square end (unless you have a tap handle, which is what it is made for).

Luke52

I can't actually get vice grips onto the bolt. The bolt actually sits flat against the surface

We sell them at work, I'll pick up a set when I can

I needed a new set of hex wrenches, so I spent the extra dollars to buy a decent set over the weekend. The bolt is fairly rounded off, and that didn't work.

Thank you, and thanks to all others for your suggestions, I'll let you know how I go

flanso 

A six point socket will usually work on hex bolts or nuts, even ones that are severely rounded.

HillRider

How do you get a socket to work on a recessed allen bolt?

operator

What, you've never used a socket on a recessed allen bolt before? Come on!

HillRider

Oh, of course!!! (smacks forehead), what could I have possibly been thinking!!!

dperreno

Just use a mirror!

flanso 

Please forgive me. My '72 Lambert uses inch sized hex bolts; no allen heads at all.

I_bRAD

Don't touch it until you need to. Also, put the ezout into a tap handle, not a drill.

MrPhil

Torx drivers also work well for engaging rounded out bolts.

LarDasse74

There was a company that used to make aluminum derailleur hanger replacement bolts - they were intended to be a break-away for use on frames that did not have a replaceable derailleur hanger. I mention this because I find it odd that the bolt on your derailleur stripped. I can think of three possible reasons why it happened:

1. Aluminum bolt and overtightened
2. Steel bolt corroded and completely seized into dropout threads
3. Wrong size allen key used (like you used an imperial size instead of the correct metric).

Of course none of this helps you get it out... as others have said, a large flat screwdrived put in place with a hammer could be the ticket.

Good luck!

flanso 

Luke52

I used the correct size allen key, a 5mm. Problem was that it was old and worn, and beginning to round off. It slipped once under a small amount of torque and that was the end of it. Any efforts to loosen resulted in further slipping and stripping.

pidda

I'm having almost the exact same issue, though i think i can get the screw out one last time before it's completely rounded out. The question then,

Are the screws that attach the hanger to the frame standard? I'm looking for a screw fitting a fuji team sl; looks like a 8mm M4/5 or something close to that?

something like this, maybe: mcmaster link

Luke52

This is the small bolt which attaches the hanger to the frame, not the derailleur to the hanger. It's similar to a chainring bolt.

This is my spare bolt..