Below: I caught quite a few filings. Above: Hole drilled already and screw extractor inserted...: I drilled into the broken off screw extremely carefully: I used new HSS Co drill bits. Starting with 2mm, then 3.2mm, 4mm, 4.5, 5. Since I knew the length of the bit stuck in there (by comparing with the bolt from the other side (which I got out), I used a marker on my drill bit to that I knew, when I would get to the end of the bolt (making sure I would not continue on drilling into the engine behi