4 ways to fix stuck bolts

And be able to use them again and again

By David ZimmerDavid Zimmer


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“Nuts! The bolt is stuck!” Nothing at the cottage feels more like progress than installing threaded fasteners. When new, they slip together with smooth mechanical precision. Removing recalcitrant and rusted ones, however, can be a frustrating experience, a counter-clockwise conspiracy punctuated with oaths and epithets and a handful of scraped knuckles.

Old age and corrosion, particularly between dissimilar metals, are the usual fixatives that keep fasteners from coming apart. When complete destruction is permissible, removal is a cinch, as hacksaws, grinders, cold chisels, or a cutting torch will easily win the day. The process gets complicated, however, when you can’t afford to damage the fastener you are trying to extract or the hole it’s screwed into.

Faced with an obdurate fastener, the first rule is to use the right tool for the job: Don’t just grab any screwdriver or wrench that’s handy and have a go. The tool should be an exact match, particularly with slot-head screws, where the slightest play between the slot and the driver tip will quickly ruin the slot. To begin, always clean away gunk, crud, and rust and give fasteners a sharp rap with a hammer to encourage corroded parts to separate.

Heat and oil

If you have the time, several applications of penetrating oil over the course of a day or two can sometimes break a corrosion bond. Alternatively, repeatedly heating a bolt with a narrowly directed propane torch, then letting it cool, can cause the metal to expand and contract enough to break the hold. Direct heat to the fastener, not the material it’s threaded into, and try to work the bolt with a wrench during the process (wearing heavy gloves).

Screw jobs

With regular steel or aluminum screws it sometimes helps to seat the screwdriver into the head by whacking it firmly with a hammer. (This won’t work with hardened- or stainless-steel screws.) To avoid ruining the recess that the driver fits into, you want to apply as much downward pressure as possible when backing out the fastener. A brace and screwdriver bit can work wonders, or you can attach a pair of locking pliers to the shaft of the screwdriver (many have square shanks for this purpose), then use that extra leverage to turn the tool while you bear down with all your might.

When all else fails, you can turn to a screw extractor, a drill-bit-shaped tool specifically designed for the task. First, you drill a hole, slightly smaller than the extractor, into the head of the screw. Then thread the extractor into the hole, counter-clockwise, until it bites. With a wrench on the extractor, keep turning and the screw should back right out. Just make sure you choose the right drill bit: High-speed-steel bits are fine for aluminum and mild-steel screws, titanium bits for harder steel screws. For stainless steel, you’ll need a cobalt-impregnated drill bit.

Nuts and bolts

To gain mechanical advantage on a wrench, slip a piece of steel pipe over the end of the tool to increase its leverage. Be careful: This method can apply enough force to snap the fastener in two. (Then you’ll be really mad.) But if the head of a nut or bolt is ruined because some chowderhead tried to remove it with a pair of Vise-Grips, an extractor socket might be necessary. Similar to a screw extractor, but designed for nuts and bolts, the socket-like head has spiralling grooves inside that bite, counter-clockwise, into rounded-off bolt heads. Another clever solution for turning stubborn nuts and screws is an impact driver, a somewhat esoteric yet nifty tool that packs a lot of muscle.

Tough nuts

When a nut is irrevocably seized, jammed, or cross-threaded, a nut splitter may be your only salvation. Available in a variety of sizes, the splitter’s head fits around the nut and features a hardened steel chisel that screws in from the side. By tightening the chisel with a wrench, an incredible amount of force is applied to the side of the nut, causing it to either split or deform enough so you can remove it. Nut splitters are simple yet amazingly powerful (always wear safety glasses), and without much wrenching effort can crack even large stainless-steel fasteners.

Removing seized fasteners can be a frustrating business, but resist the urge to attack with brute force when you’re trying to get that mounting bolt off the motor or loosen the pump’s drain plug. If the air was blue with expletives when you rounded that hex bolt, think how foul it will be when you fatally crack the water pump or rip the starter off the old Evinrude. Be patient, regulate your breathing, and use the right tool for the job.

This article was originally published on March 22, 2007

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David Zimmer