My friend Nick and I had a discussion the other day about which bolts were tougher to break free: shaft coupling bolts or the lug nuts on an old trailer. Nick pointed out that lug nuts spend more time underwater and are usually torqued down a whole lot tighter than a shaft coupling screw. On the opposite side, I argued that shaft coupling bolts require you to assume the yoga pose “Downward Pretzel” just to see the bolts. The argument was never settled, but this week, I was reminded that even the most stubborn bolts can often be coaxed loose with a judicious application of penetrating oil and some muscle.
The muscles, in this instance, were those of Dustin Rahl, owner of a very busy mobile trailer service in Sarasota, Fla., Trailers 2 Go. The axle on the trailer for our Catalina 22 test boat Jelly (aka Our Lady of Perpetual Despair), had cracked at the weld, so that its left wheel splayed outward at a 20-degree angle. Dustin arrived early Tuesday to remove the axle, which was rusted beyond hope, so that he could measure it and order a new one. Alas, the lug nut bolts stood in his way.
He didn’t even bother to try them cold. “I’ll just give it a shot of PB Blaster,” he said.
We've tested spray petroleum products to a fare-thee-well. Some are good for loosening bolts, others for sealing electrical connections, and others for protecting against corrosion. When it comes to loosening bolts, we’ve found the PB Blaster works best. That’s not to say the others won’t work. It’s just that when it comes to the really tough bolts, PB rises to the top.
But what happens if the PB isn’t enough? Carefully applied heat from a butane, MAPP-gas, or propane torch is usually the next step. After that, it’s time to break out the specialty tools.
Like a chef with a favorite set of sauce recipes, a good mechanic needs a tried-and-proven list of tricks to help coax rusted fasteners into submission. Their tools range from penetrants and ingenuity to pure brute force. A breaker bar for sockets and the learned wisdom of just the right amount of torque works much of the time. For really stubborn fasteners, there are nut cutters, and a wide range of torque- and shock-inducing gadgets.
One unusual but effective fastener-freeing technique involves massive thermal change that causes an abrupt material expansion or contraction. A piece of dry ice is pressed against a stubborn bolt head to shrink its dimensions. This results in the disruption of the rusty bond and more willingness for the bolt to turn.
Less esoteric solutions include box or socket wrenches with fewer facets, which afford a tighter grip on a nut or bolt head and allow more torque without stripping the hardware. The better your ability to apply force, the more careful you must be to avoid breaking the fastener.
Sometimes, all a bolt needs is a few good wacks to loosen the bond, but be careful! You don't want to damage the threads. If you can only approach from the threaded end of a bolt, you can put another nut on the bolt and tap that — not too hard. Alternately, you can use a rubberized mallet, or a piece of hardwood to insulate the bolt from the hammer.
The rusting process also degrades bolt head shape. A last ditch effort may require a pair of Vise-Grips or sockets designed to grab deformed bolt heads. For stuck, slotted-head bolts, an impact screwdriver can be a real lifesaver.
Frozen, rusted nuts present a similar problem, but there are tools that allow you to split the nut without destroying the bolt. Nut crackers use a chisel-like edge that is screw-pressed against the side of a nut. Once the tool is tightened, a machinist’s hammer is used to smack the tool, and its blade splits the nut.
I’d be interested in hearing of other tried-and-true methods for un-seizing the seized.