| B*stard Well-nuts!
So getting them out isn't too hard when you have the right torx bit, but when they're so siezed that the torx bit snaps off in the bolt you know you're in trouble...
There was no way I was going to drill it out now (I should have done that earlier I guess, but hindsight is a wonderful thing...) especially with the hardener torx bit in the hole.
There was no room to cut through the bolt from behind the panel, so I ended up making three very cautious (and nervous!) cuts across the head with a junior hacksaw to take the head off and push the bolt through.
All sorted now and the black replacements look very smart against the red panel.
/vent | 
antonye
Threaded Mode