Drilling out a broken bolt

The threaded hole in which part of the bolt remains can be left undamaged by doing the following.

1. Point the bolt fragment exactly in the center. To facilitate punching, file the break with a file, if possible.

2. Drill out the broken bolt. The drill diameter should be 0.8 of the thread diameter. For example, for an M6 threaded connection, the drill diameter should be 4.8 mm.

3. To drill large bolts, use a small diameter drill first.

4. Remove the parts of the bolt left after drilling and «pass» tap thread.