My Subframe Bolt Broke off, so How Do I Get the Bolt Out?by Don Kress
Once a bolt has broken or sheared off its head, an inevitable sense of panic always strikes the one who broke the bolt. Because the subframe bolts on most vehicles are so low to the ground, this is a fairly common occurrence. Whether the bolt is stuck and breaks due to having rusted, or simply just rounding off the head of the bolt because you applied too much pressure in the wrong direction, removing these bolts can be accomplished, although it won't be easy.
Insert a drill bit into the electric drill that is approximately half the diameter of the bolt that needs to be removed. Make certain to run the bit all the way down into the drill's chuck to help prevent the drill bit from breaking, particularly if the bit is less than 1/4 inch in diameter.
Apply a drop of machine oil onto the tip of the drill bit. This will help combat the heat that will build up in the tip of the bit and help it to stay sharp. Excessive heat in the drill's tip will turn the bit bright red, which eliminates the hardening of the steel and dulls the drill bit.
Drill into the center of the broken bolt, moderating your speed between slow and medium. Drilling quickly will cause the drill bit to overheat. For every 1/8 inch you drill into the bolt, apply another drop of machine oil and allow the drill bit to cool off slightly.
Drill through the base of the broken bolt and then remove the drill bit. From here you have two options. You can attempt to use a bolt extractor if you want. The heat from the drilling process will have constricted the bolt slightly. To use a bolt extractor, insert it into the hole you drilled and tighten the extractor in place with an adjustable wrench. This will lodge the extractor into the bolt shaft. Continue twisting until the bolt comes free and can be removed. In some cases, however, this option will not be effective. In these cases, you will have to continue drilling and then clean out the threads.
Insert a drill bit into the electric drill's chuck that is the same size as the bolt shaft, but smaller than the outer diameter of the bolt's threads.
Drill out the rest of the bolt shaft in the same way in which you drilled it the first time, using a slow speed and applying machine oil to prevent the tip of the drill bit from overheating.
Clean the threads of the bolt hole by using the tap and die set. Taps look similar to drill bits, but they have threads on them just like a bolt does. Choose a tap that is the same size as the original size of the bolt, then attach the tap wrench included with the kit to the tap. Run the tap into the bolt hole and it will clean the metal shavings out from between the threads so that you can install a new bolt in the old bolt's place.
- Whenever removing subframe bolts, it's helpful to heat them up with a propane torch prior to attempting to remove them. This causes the metal to constrict slightly, loosening the bolt just enough to work it loose.
Items you will need
- Electric drill
- Drill bits
- Machine oil
- Screw extractor set
- Tap and die set
- "The Complete Idiot's Guide to Restoring Collector Cars"; Tom Benford; 2004
- "The Restoration Manual: The Complete Illustrated Step-by-Step Guide"; Lindsay Porter; 1994
- "How to Restore Your Collector Car: 2nd Edition"; Tom Brownell; 2009
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