Hey folks, welcome back to the shop. Today we’re talking broken bolt removal. There’s no one specific tool for it, or there probably is, but I’m going to show you a few tips I’ve learned as a maintenance mechanic. Since it’s hard to work on a real broken bolt and film it at the same time, I made a simulated one: a 3/4 inch bolt in a nut standing in for the threaded hole, sheared off with a cutoff wheel on a grinder.
Disclosure: I buy most of my own tools, and sometimes companies send me items to test. Nobody has ever paid me for an opinion. As an Amazon Associate I earn from qualifying purchases.
Quick Take: My Broken Bolt Ladder
Start simple, then work up: grab it, chisel it, then go to a left-hand drill bit.
- Pliers on leftover threads: fastest when it works
- Chisel and hammer: slow, but it works
- Left-hand drill bits often back the bolt right out
- Drill press or mill with reverse: most of the time they come right out
- Rusted, seized bolts take patience
- Banged-up threads can mean extractors or more
- Cheap left-hand bits don’t hold an edge as long
Best For: Maintenance techs and anybody fighting sheared bolts
Step 1: Broke Flush on a Guard? Grab What’s Left
We’ve got a lot of safety guards on our equipment, on rollers and conveyors. Say somebody bumped a guard with a forklift or another machine kicked it over, and the bolt broke. Usually it breaks off flush with the guard. Best case, you get the guard the rest of the way off, the bolt head is gone, but you’ve still got threads sticking out. There may be a rough edge or some metal smeared over, so it might be caught, or you might be in good shape.
If it went in with anti-seize and isn’t corroded or rusted shut, you might be able to back it out by hand. Be careful, because you’ll probably have sharp edges. If it’s a little tighter, grab some Channellocks, or Knipex Alligators or Cobras. Get on the threads and work it back out. Don’t worry about the threads, since that bolt is a goner anyway. You can’t put it back in and tighten it up.
Step 2: At or Below Flush? Chisel It
If it’s seized up a little, say you forgot the anti-seize, and it broke off right at flush or a little below, get a small chisel on it. That’s the best case. If it’s an engine bolt or the like, we all know it’s going to be one monolithic piece with the block, corroded in good and rusted shut. Catch one corner with the chisel and use your trusty ball peen, a sledge, or even a claw hammer. If you can get it to bite on the edge and turn a little, you can work it out. This is a patience game. I’ve done many of them like that, chiseling them around until they back out far enough.
Once it’s up a little, my Knipex Twin Grips have the little grips on the front that’ll catch it. I’ve pulled many a bolt with those using just the little bit of smudged-over metal, enough to get it out far enough for a better bite with Channellocks or the Twin Grip’s side grips. A little baby set of Channellocks is better for smaller bolts, since you can get in tighter. More on those in my Knipex Alligator and Twin Grip review.
Step 3: Left-Hand Drill Bits
These are lifesavers. I carry them in my bag. The spiral runs left-handed, so you put your regular drill in reverse, and it cuts the opposite way from the standard bits we all use. The set in the video is a cheaper set. They work, but they don’t last as long as the Century brand I carry at work, which holds an edge better, so you aren’t sharpening all the time. I used a 20-volt drill.
Good practice, if you can get to it: take a punch and put a little notch in the center first so the bit doesn’t walk. Then run it in. One of two things happens. Best case, the drill goes in a little, catches, and backs the broken bolt right out, lefty loosey. Otherwise, you’ve got a hole started for easy-out extractors. I’ve found this works in most cases, most of the time. Use a smaller bit for a smaller bolt. For the demo, I used the second-largest size, and it took a minute to bite. Then it came right out.
If you can get the part to a drill press or a mill with a reversing drive, I’ve seen these work 98% of the time. Put a little downward pressure on the handle, it pops in there trying to cut, and it reverses those threads right out. If the threads are banged up, it’ll be harder to catch, and you may have to go to more extreme measures. If you’ve drilled a good hole and it still hasn’t backed out, get a screw extractor, the kind you hammer in, and back it out with that.
| Situation | What I reach for |
|---|---|
| Broke flush, threads exposed | Hand, Channellocks, Knipex Alligator/Cobra |
| At or below flush, seized | Chisel and hammer, then Twin Grip front grips |
| Small bolt, a little exposed | Baby Channellocks |
| Below flush, nothing to grab | Center punch, then left-hand drill bit |
| Bit drilled through, still stuck | Hammer-in screw extractor |
Why I Go Left-Hand First
A guy I worked with loved chiseling bolts out, even small ones, quarter inch or less, little metrics. It would take him about 10 minutes. Sometimes you don’t have that kind of time, because you have to get the machine back up. So I’d always go to the left-hand bits. I learned them from an old guy with an almost photographic memory of the machinery. He’d tell you there’s a hidden 3/8 bolt under that bracket you can’t see, and you’ll have to get the other bracket off first. A fountain of knowledge. Shout out to Wayne.
The Bottom Line
First, see if you can get some teeth on it and back it out. Sometimes it works, sometimes it doesn’t. Second, work it around with a hammer and chisel. Third, a left-hand drill bit, and an extractor if it still won’t come. And next time, use your anti-seize. The pliers I use for this are in my top 5 Knipex tools, and the Knipex Cobra ES is the newest one in my bag. Be careful out there.