Replacing a rear mech the other day on a Cove handjob steel frame and despite taking care and cleaning the threads out, I ended up threading a good portion of the frame mount without knowing it – It seemed all square and just a little tight , but I now have a rear mech attached but at a slight angle. Its not a major pain but it will be if I need to replace the mech. Any idea how to tackle this ? Is it an LBS job to get the thread re-instated on the frame or is there a fix I can attempt?

Depending on how cross-threaded it is, you could remove the mech and run the screw through carefully from the other side to re-cut the original thread path.

All depends how knackered it is to start with……?

you can drill it out and fit a special thread thing.

http://www.tritoncycles.co.uk/products.php?plid=m4b107s192p1803&rs=gb

If your mech is on at an angle you are going to get horrible shifting. Try taking it off and putting it back on straight.

Thanks for the suggestions folks. Think it may now be pretty knackered threadwise but reluctant to take the mech out in case it means I cant get it on again.
I did try threading it from other side but no joy getting the thread started and also attempted for about a half hour to get the mech on straight, but only way it gets any bite on the threads and stays put is when cross-threaded in at a slight angle. Shifting is actually ok , but not perfect. Will look into the drillign and re-threading thing. cheers