How To: Broken bolt removal - odd shaped surface

[Grant Bowker]

I think we've already had mention of welding a nut onto a broken off bolt to permit wrenching out of its hole. Recently Bob Carriere and I met a situation where this kept failing for us. We were working on the brackets that mount rear view mirrors to cab 12 and 13 Chevrolet (Canadian in this case, don't know if Australian used different brackets). We could weld the nuts on securely, they would make a small segment of a turn, just enough for us to feel that the "rust weld" might be letting go, and then the nut would fall off. We ended up thinking the nut was being levered off the bolt due to the bolt hole not being perpendicular to the surface of the bracket - resulting in a lever action. The method that finally worked for us was to drill a pit into the broken bolt to increase the weld area and heat penetration for thermal effect (as the weld cools it shrinks, even if only a small amount) to shringk the bolt and help break the "rust weld"., then weld a sturdy sheet metal arm to the bolt. The first arms we tried were flat and levered off like the nut - we shouldn't have been surprised about that. Then we used the ball end of a ball-peen hammer (a small one, 8oz.) and a hole in Bob's anvil to create a rounded surface on the arm. Drilled a hole in the middle of the dimple, welded it to the bolt and turned. on 1/4-20 bolts, hand forcce worked on some, others need hammer tapping on the arm to break the bolt free. Photos show the mirror brackets being worked on, the arm before welding, after welding and the stub bolt attached to the arm after removal.

[Jordan Baker]

Good tips. I found when trying to get some threaded parts from cast I also used lots of heat and ATF oil.