Every carpenter, mechanic, builder, and home improvement enthusiast has experienced the frustration of breaking a bolt. It only takes one turn too many of a wrench to cause that horrifying “snap.” Without specialized tools, it can take hours or days to remove a broken bolt. Fortunately, all the tools needed to perform the extraction, along with replacement bolts of every kind, are available at hardware stores or at competitive prices on eBay. Simply owning the right equipment is not enough, however. It is crucial to know the recommended procedure for removing a broken bolt, or the entire project is at risk. Even the most experienced consumer may need a refresher.
For best results in removing broken bolts, a bolt extractor kit is required. These kits come in various sizes and levels of complexity, ranging from just a few included pieces to sets with dozens of parts. The chart below outlines some of the pieces that are typically included in a bolt extractor kit.
|Washers||Thin, disk-shaped plates made of hardened steel with a hole in the center|
|Taps||Cutting tools used to create internal threads|
|Tap Drill||Used to insert tap|
|Tap Drill Bushing||Used to guide tap drill|
|Drill Bits||Used to drill a new hole inside the broken bolt|
|Extracting Bits||Also called Extractor Pins or Extracting Core Bits
Inserted into new hole inside broken bolt to aid in removal
An alternative to purchasing a bolt extractor kit is to use are versible drill and left-hand drill bits. For professional carpenters and mechanics, a kit is a wise investment. For occasional home improvement projects, the drill and bit may suffice.
Removing the Broken Bolt
Once all the tools are assembled, the procedure for extracting the broken bolt can begin. There are five relatively simple steps to achieve the removal of a broken bolt.
- Flatten the Bolt
A broken bolt leaves a jagged, uneven surface. This can cause the drill bit to move off-center, impeding removal, or can cause the drill bit to break, making the problem worse. Use a metal grinder to smooth out the surface where the bolt broke. If the bolt snapped below the surface, use a metal punch to even out any jagged edges, so the drill bit can make a hole in the center of the broken bolt.
- Drill a Pilot Hole
Using a small drill bit, make a small hole in the center of the broken bolt. It can be helpful to use a heavy hammer and punch to create a dent in the top of the bolt for the drill to follow. Test the hole to see if it is large enough to insert the extracting bit. If not, drill another hole with a slightly larger drill bit. Start small and work up to larger bits, because if the hole is too big for the extracting bit, removal becomes much more difficult.
- Insert the Extracting Bit
Place the extracting bit into the hole and secure it to the broken bolt. Use a vise grip to apply moderate pressure while turning the extracting bit counter-clockwise. The bit should bind into the broken bolt. If this proves difficult, tap the extracting bit gently with a hammer to press it into the bolt.
- Remove the Bolt
Continue to turn the extracting tool counter-clockwise until the broken bolt comes completely out of the surface into which it was stuck. Take time and care during this part of the procedure to avoid breaking the bolt further or damaging the material in which it was embedded.
- Clean Out the Hole
During the extraction, small metal filings often come off the bolt. These must be thoroughly removed before replacing the broken bolt with a new one. Hold a heavy-duty magnet over the hole to attract the filings and shavings. Spraying a small amount of compressed air into the hole ensures that all debris has been cleared out.