Trying to change the bent mech hander on my old Hustler. It has three small 2.5mm allen bolts holding it on. One of the bolts has rounded. I have tried using a Torx tool, a selection of different allen keys and am in the process of filing down a 3mm key which is very tedious using a leatherman. I do not have a drill at my disposal.

Any ideas?

drill/bolt extractor would be best option but otherwise hammer a torx bit into it

Go and beg for help at the local bikeshop!

Take cake and look desperate and embarrassed.

Cut a slot with a hacksaw and use a screwdriver.

If you don't have a extractor tool.

I have epoxied in a sacrificial allen key before.

If you have a dremel or similiar, cut a slot with a small cutting wheel. Has the advantage of also putting a load of localised heat into the bolt.

a brand new hgh quality allen key might have undone it previously, but not now you;ve used a torx head. any of the sugestions above are fine, epoxy in a sacrifical allen key, cut a slot and screwdriver it, drill it, or try and hammer in a slightly larger allen key.

used a dremel to cut a slot – cheers for the tips!

Can you get a small multi tooth socket on the outside of the bolt you will need to tap it on with a hammer, has worked for me many times.

I use a larger Spline tool, tap it in with a hammer, then remove after soaking the bolt in WD40 or the like, It damages the spline toll slightly but it's quicker then cutting a flat head screw it it.

A shaped C4 charge.

Can you hammer in the next size up torx bit? Works sometimes depending on the size of rounded hole