[header] How to remove a broken bolt [title] Center punch the broken bolt as close to the center as possible. [step] Using a hammer, mark the center of the broken bolt with a center punch. This will help you drill into the center of the bolt as closely as possible, putting you at less risk of damaging the threads of the broken bolt. 
[title] Drill a pilot hole into the center of the broken bolt with the left-handed drill bit. [step] A left-handed drill bit is threaded in the opposite direction, so the reverse setting on your drill is what will actually drive in the bit.