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If you are planning to restore a car that is even a few years old, you will undoubtedly come across the odd nut, bolt, or stud that is rusted solid and won't come off. This project will expose you to some of the methods used by several of the "experts" in the field.
The first step in getting rusty or stuck fasteners off is to perform a preemptive strike. It is often the case that you find a nut or stud will not come off after you have already stripped or damaged it. If you think a nut might give you problems, it's far better to tackle the removal process carefully rather than destroy one of your precious parts.
If you are planning to remove an old rusty bolt in a day or two, soak the area with a good penetrating lubricant like WD-40 or liquid wrench. The lubricant will seep down and penetrate the joint, making it easier to remove and break apart. This seeping process takes time, however. At the very least, soak the bolt the night before you attempt to remove it. This will place you a step ahead in the battle.
When removing these old bolts, you must have the right tools for the job. A properly fitting wrench is essential. People often use the wrong tool for the wrong bolt. The female Torx bolts are an excellent example. A simple hex socket tool will sometimes fit onto the bolts, and you may be able to remove some of them, but chances are one of the bolts will become stripped. Using the right-sized tool to remove a fastener means you are increasing the odds it will come off easily.
For pulling studs, Snap-On offers an excellent collet-based stud-removal tool that does the job very well without damaging the stud. This tool incorporates a collet that latches onto and compresses the threads of the stud, squeezing them tight. Then the tool and the stud can be removed. If you are removing studs from an engine case, an extra vise-grip or two might be useful as well to get more torque on the studs.
Exhaust studs are sometimes difficult to remove from the heads, as they rust and corrode very easily. Make sure you lubricate the area heavily before even attempting to remove a rusty exhaust manifold. Unfortunately, if a stud snaps off, there really isn't too much you can do. Since the studs are heated by the exhaust, they become very brittle over time. The only way to remove a broken head stud is to have it drilled out or removed using an EDM process.
A common propane torch or, even better, an oxy-acetylene torch may help you out when you need to remove bolts. These torches are available at most hardware stores and are useful beyond belief. A torch can give you an extra advantage in removal, particularly on bolts and studs that have had red Loctite 271 used on them.
With the torch, heat the metal surrounding the stud. This will help melt any Loctite on the threads and will also help expand the metal that is surrounding the stud. Use caution, though; do not apply heat directly to the stud, as this will heat the stud, and it will become even more stuck in the hole. If you are removing a stud from an engine case or a cylinder head, you will find it takes a surprisingly long time to heat up the case. Aluminum and steel conduct heat very well, so focus the torch on the case for a while before you try to remove any studs. Also, be sure to use the torch only in a well-ventilated area.
On the opposite side of the equation, you can sometimes use coolant to help remove a stuck bolt. One of the best-kept secrets is the "compressed air in a can" your local office supply store sells for blowing dust out of old computer equipment. If you hold the can upside down, the gas inside (which is not actually ordinary air) will drip out as a very cold liquid. You can drip this liquid onto bolts and into areas you might be having trouble with. Be careful, though. The cold will have a tendency to make the metal increasingly brittle and prone to breaking. Always use eye and skin protection when using coolants, as they can be deceptively dangerous.
The application of heat and cold together can be a powerful combination. As the joint heats up and then cools again, rust and Loctite may break free from the rapid expansion and contraction. There is no exact science for this, so trial and error is the rule of thumb.
Another important point is to make sure that the nut or bolt you are trying to remove can actually be removed. Often someone will try to remove an embedded stud or a nut that has been welded on, only to find that this is an impossible task. Before you dig out the angle grinder, check and double-check to make sure you aren't missing something obvious.
Sometimes it makes sense to weld a nut to a stud that is stuck and immovable. Doing this will allow you to place a wrench on the nut and, hopefully, remove the stud. Before you attempt to weld, make sure that you clean all of the rust, debris, oil, and anything else that might be on the stud. Sometimes the stud will be old and brittle and may not take well to welding, as is often the case with exhaust studs. Also, you can only effectively weld most studs if they are made of steel. Some alloy studs you cannot weld--the nuts just break off as soon as you try to turn them.
The impact wrench is another useful tool and is most helpful when you are trying to remove a nut that rotates on a bearing (for example, the steering wheel nut) or one that is attached with a great amount of force. The impact wrench "hits" the nut with repeated blows, knocking it loose, which will save you plenty of time when you need to remove specialty bolts. There are two types of impact wrenches available--ones that run on compressed air and simple electric ones that plug into a standard household socket. I recommend the electric style if you don't have an air compressor.
My weapon of choice when all else fails is the Dremel tool or its big brother, the angle grinder. These two tools of destruction really don't stop at anything when it comes to cutting through metal. The Dremel tool is my personal favorite because it is so small and you can place it in so many different positions. Adding to its versatility is that you can add a flexible shaft to the tool that allows you to put the rotating blade just about anywhere you can reach.
The Dremel, or rotary, tool spins at about 50,000 rpm and uses small ceramic-like discs to cut and grind through steel. There are other small fiber-reinforced discs available that are more expensive than the regular discs, but they last longer, and are more effective at cutting through steel quicker. I recommend using thesediscs, particularly if you can buy a large bag of them at a swap meet or other venue. Make sure you don't ever use the Dremel tool without eye protection.
The angle grinder makes no apologies for being the most destructive of all the tools in my collection. The grinding wheel can grind, wear, cut, and melt away steel much faster than any other tool I own. It's especially useful for grinding off nuts and studs that are so badly rusted there is no way to get a grip on them. Make sure you use appropriate eye, ear, and nose/throat protection when using the grinder, as this tool kicks up a lot of small metal particles.
When all else fails, you can sometimes use a hand drill to bore out an embedded or broken stud. While not the prettiest solution, the hand drill is still an effective method of removal. For greater success with a drill, start out with a very small drill bit and gradually increase the diameter. Also, use plenty of lubricant. When the hole you are drilling gets to be about the size of the stud, try to remove the remains of the stud using a pick. Be careful not to damage the threads of the hole by drilling too large of a hole. When you are finished, chase a tap down the hole to clear out the threads, or if it's damaged, thread the hole to a larger diameter.
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The propane or oxy/acetylene torch is one of my personal favorite tools. Make sure you heat the case and not the stud. You may notice it takes a long time for the case to warm up. Keep the torch focused on the area and don't let it stray onto the stud. The white inner portion of the flame is the hottest; the blue part indicates a cooler region. Make sure you only use the torch in a well-ventilated area, as the propane will create harmful carbon monoxide gases.
The tools of destruction and mayhem are shown here. The Dremel rotary tool (right) with flexible attachment is best suited for cutting off small nuts, bolts, or studs. This tool will solve about 95 percent of your problems. The angle grinder (lower left) is for more serious tasks where you must completely grind down rusted nuts. WD-40 is an excellent penetrant for removing rusted and stuck bolts. The Snap-On stud remover (upper left) is a hard-to-find tool, yet very useful for removing those troublesome studs. Finally, the electric impact wrench (center) is good for removing nuts that have been mounted with a lot of torque.