I recently moved into a new house. Within days, a PVC double-glazed window handle snapped. To replace it I tried removing the two bolts securing it. One came out fine, the other head sheared off surprisingly easily exposing a rusty thread.
To remove the thread, firstly I soaked what I could in copious amounts of WD40 and let that set in daily for a couple of days. Then I tried using pliers to rotate the thread but due to the fitting couldn't get a good grip.
Secondly I got a carbon steel screw extractor set. The first hole I drilled was quite small. The smaller extractor lost its thread before the bolt started to move. The second pilot hole I drilled let in the larger size. It gripped into the bolt but after some give the bolt instead broke along the pilot hole I drilled. You can see that rust had started to eat through part of the bolt, which you can just about see in the image.
I need to remove the last few mm of the screw without damaging the hole in the window frame so I can replace the handle. Any advice?