Few things seem more hopeless than when you’re in the process of removing a bolt, screw, or stud and it breaks. At that point, you know it’s all over but the crying. You’ve busted a bolt off in a casting and haven’t the faintest idea how to get it out. There it is—what’s left of a bolt or screw stuck, and it’s put a halt to your progress.
Sometimes, it’s as simple as a hammer and a chisel along with a pinch of tenacity to get it out. When the hammer and chisel approach won’t work, you’re going to have to try and drill the fastener out and remove it with a bolt extractor. And if that doesn’t work you’re going to have to drill the fastener out just shy of the threads in hopes you can gently remove the remaining bits stuck in the threads.
Broken fasteners are nothing new, which is why the tool trade has come up with some innovative ways to remove broken bolts and studs. Summit Racing Equipment and Harbor Freight have a number of solutions for your bolt extraction headaches, and we’re going to show you a few of them here.
Ideally, you want to be able to remove the bolt or stud while keeping the threads intact. If the threads become badly damaged and are not salvageable, you will have to repair or replace them, which calls for a coil thread insert like a Heli-Coil, available from Summit Racing Equipment. The Heli-Coil insert is a clever idea where you drill out the damaged threads, tap the hole, and screw in the precision Heli-Coil threaded insert.
When you’re drilling out the damaged fastener, you want to get the hole as dead center as possible, which can be challenging depending on the nature of the damage. Center-punch the broken fastener and drill a small pilot hole to get started. You do not want to, under any circumstance, break the extractor off in the fastener. Because the extractor is traditionally harder than most drill bits, you will then never be able to get the broken bolt out.
Another option is to weld a bolt to the broken fastener and attempt removal. The downside to that approach is the risk of welding the bolt to the iron casting, which will only make the problem worse. Welding a bolt to the broken fastener should only be attempted when there’s enough of the fastener sticking out of the casting.
1. A broken bolt can be hell to remove, depending on why it broke in the first place. If the bolt broke due to corrosion the chance for a successful removal is low because it has likely become permanently stuck. However, if it sheared off due to a material failure, you stand a better chance. With the tension off a bolt shank it can sometimes be removed with a chisel, as shown, and be unscrewed out of the hole.
2. Begin bolt removal by using a center punch to mark the pilot and plan on drilling out the bolt for the insertion of a bolt extractor.
3. Start with a small 1/8-inch pilot hole, which will serve as a guide for the larger drill bits to come. You want to progressively bore out the bolt extraction hole until there’s not much bolt shank left. This will make bolt removal easier.
4. We’re now using a larger 1/4-inch drill bit, and drilling a little deeper.
5. The 1/4-inch bolt extractor hole has been drilled and is ready for the extractor tool we got from Summit Racing Equipment. We will admit to you that this hole isn’t dead center.
6. A bolt extractor is basically a super-coarse left-handed thread affair that screws into the bolt shank for removal. You may have to carefully apply heat to the casting or forging to allow expansion around the bolt shank. Penetrating lubricant can also be used around the bolt. Whatever you do, never break a bolt extractor off in the bolt shank. Because the bolt extractor is typically harder than the drill bit it will be impossible to drill out.
7. The bolt shank has been successfully removed. Clamp it into a vice and remove the extractor.
8. Clean threads make for easier bolt installation. Use a thread chaser (also known as a thread cleaner) to clean up dirty or damaged bolt hole threads, using a penetrating lubricant. When threads are badly damaged, you may have to opt for a Heli-Coil threaded insert for thread replacement.
9. Note the slots in this thread chaser. They’re designed to carry debris away from the bolt hole while you’re cleaning threads.
10. Run the thread chaser through the hole several times until all debris is gone. Flush the hole out with penetrating lubricant. While you’re at it, chase all bolt hole threads in the casting to ensure cleanliness.
11. Spark plug hole threads are another bone of contention, especially on aluminum heads. If the threads are damaged you can chase them as shown. Heli-Coil threaded inserts are also available for spark plug holes damaged beyond repair.
12. Using a penetrating lubricant and a spark plug thread chaser, gently turn the chaser in and back it out until it turns smoothly.
13. Equip yourself with a high-quality titanium or cobalt drill index from Summit Racing Equipment, which is good to have on hand for many purposes. When you’re drilling out broken fasteners you want a super-hard drill bit to cut the fastener. If you opt to buy drill bits on the cheap, they won’t last.
14. The OEM Automotive Tools 10-piece bolt extractor set from Summit is a high-quality set that includes five mechanics-length right-hand cobalt drill bits and five tapered chromoly extractors. This is what you want for a wide variety of stubborn removals.
15. The Summit Bust-N-Out bolt extractor kit (PN SUM-902375) comes in a variety of sizes for broken bolt removal. Each specialty end carbide burr tool is made for specific bolt hole sizes to properly prepare the broken surface. This greatly increases your ability to drill the broken bolt on center, increasing the odds for saving the existing threaded hole.
16. Here’s the Summit Bust-N-Out (PN SUM-902437) for larger broken bolt challenges. The beauty of Bust-N-Out is ease of use. Everything you’re going to need is here to get a stubborn broken bolt or stud out.
17. Another issue facing enthusiasts is plugs that are seized, like this one in a Chevrolet intake manifold. These steel plugs become seized due to dissimilar metal corrosion where steel and cast aluminum get together. Removal of seized plugs requires a lot of caution. If you are careless you can permanently damage the casting. Removal begins with drilling out the plug for extractor use.
18. JGM Performance Engineering carefully heats the aluminum, keeping in mind that aluminum melts at 1,300 degrees F. You want it hot enough so it expands around the plug or bolt, but not so hot that it melts or distorts the casting.
19. The plug extractor is inserted here as shown; with a gentle counterclockwise twist to get it started. It is a good idea to soak the plug with penetrating lubricant days beforehand to help break the bond between the steel and aluminum.
20. A stubborn plug, once the aluminum has been heated, is cooled with dry ice to aid contraction to where it can be loosened.
21. The steel plug has been broken loose and is ready to come out. Stubborn plugs often have to be drilled out to where there’s not much plug left.
22. This Warrior pipe nipple extractor set from Harbor Freight is designed to free pipe nipples from fittings without cracking, marring, or scratching. The extractors are made of durable heat-treated steel and feature a zinc plating for rust and corrosion resistance.
23. The Performance Tool five-piece bolt extractor set from Summit Racing reduces the frustration of removing stubborn nuts and bolts. What makes this work so well are the gripping internal edges that remove rusted, rounded, or painted nuts and bolts. These high-quality sockets are manufactured from chrome molybdenum steel for brute strength.
24. This extractor set from Harbor Freight is engineered to remove broken screws. High carbon steel construction gives these screw extractors the strength necessary to remove the most stubborn screws.
25. The Heli-Coil, available from Summit Racing Equipment, has long been the industry standard for thread repair. Heli-Coil inserts work in any material—aluminum, magnesium, cast iron, bronze, and more. Damaged threads can be restored to better-than-new condition in spark plug holes, carburetor fuel inlets, transmission and engine castings, oil drain plugs, exhaust and intake manifolds, cylinder heads, brake calipers, and suspension components. Heli-Coil is what you turn to when threads are beyond salvageable.
Photos the Author, Summit Racing Equipment, and Harbor Freight