How to remove a stuck or rusted bolt or nut

Recommendation points

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• What wrenches to use
• Pickling Lubricants and Chemicals
• What does it mean to “warm” the thread
• How to burn through a rusty nut
• How to use the nut puller
• If the hairpin boils: learning to work with an extractor
• Ways to Prevent Corrosion on Threads

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It is difficult to find a master who has never in his life encountered a stuck threaded connection. Today we will tell you about the best ways to deal with a similar problem with different types of connections and using a variety of tools and devices..

What wrenches to use

Pulling off rusted threads requires significant effort. Unfortunately, ordinary open-end wrenches are of little use for these purposes. Not only are they not effective enough, they can simply ruin a good tool. Even Cr-V horns can unbend and lose their original size permanently.

In old workshops, open-end wrenches were reinforced by welding on pieces of reinforcement and using them specifically to break off rusty threaded connections. Today, there is no need for such modifications: sockets and spanners are ubiquitous, which are best suited for breaking.

There is, however, a small caveat: wrenches and sockets with 12 or 18 break edges are not the best fit, and slippage is likely. It is better to use hex tools for breaking. It is even better if the heads have so-called swivel or screw edges. They are called so – heads for torn edges. When unscrewed, they themselves provide the required clamping force.

While it’s easy enough to find suitable socket heads, six-sided spanners are extremely rare. Nevertheless, they are indispensable for stripping nuts with a long thread overhang, where the only alternative to a ring spanner can only be an elongated head, and even then not always. Twelve-sided spanners on heavily boiled nuts are likely to become unusable.

In some situations, both socket and box wrenches are useless. Fully lapped nuts and bolts can only be loosened using pipe wrenches or self-tightening clamps. Car Service Tip: Use a small locksmith’s vise (or watchmaker’s vise) to clamp the nut with an adjustable wrench as a lever.

Pickling Lubricants and Chemicals

The processes leading to thread seizure due to rust occur on a microscopic scale. Their closest analogy at the macro level is when the cereal gets stuck in the funnel: wedging against each other, particles of rust and salts densely clog the confined space. The situation is aggravated by the fact that, oxidizing in air, rust increases in size and, as it were, expands the thread from the inside..

The easiest way to get rid of this effect is to turn the crystalline particles into a viscous mess. A wide range of liquids can be used as a solvent – from water to kerosene and machine oil. The more fluid the grease is, the more effective it is in loosening rusted threads. The advantage of multipurpose greases like WD-40 lies in high fluidity..

Note that the chemical composition of rust can vary from case to case, and attempts to lubricate a threaded joint are not always successful. An alternative would be to try to dissolve the salt deposits inside the threads using water or weakly concentrated solutions of acids or alkalis. The only drawback of this method is that the reaction takes time, often quite long. However, if you leave the threads moistened with Coca-Cola, a sink cleaner with hydrochloric acid or even plain water for several hours, then twisting a rusty nut will be much easier..

What does it mean to “warm” the thread

The problem can be quickly solved only by mechanical action on the threaded connection. In this case, the effect must necessarily be dynamic: there is no point in pressing the cereal stuck in the funnel, but if you shake it, the grains will start to wake up again.

In common people this is called “warm the thread” – to inflict a series of point strikes on different parts of the connection. It is the vibration effect that helps to loosen the stuck thread and subsequently breakdown with a conventional wrench can occur without any noticeable effort.

To warm the thread qualitatively, you need to tap the nut both along the edges and in the axial direction. Bolt strikes can also be successful. The greatest effect is exerted by the work with a perforator in the chiseling mode, but the nut must be periodically turned.

How to burn through a rusty nut

An alternative to the previous method is to destroy large crystals of salts and oxides, reducing the friction force inside the thread. This can be done due to the thermal expansion of the metal of the nut and bolt. In the simplest case, another nut is welded to the licked nut, but with a larger diameter. Due to the heating of the thread and the presence of fresh edges, it becomes very easy to untwist the thread.

Calcining the threaded connection helps in almost 100% of cases, but it is not always convenient to do this for two reasons:

1. There is no suitable equipment on site;
2. Connected or adjacent parts are heat sensitive.

However, it is not at all necessary to heat the threads white. It is enough to provide heating up to about 450-500? С, while expansion by several microns will be quite enough. Even a conventional propane canister gas burner will cope with this task..

A more sophisticated way is to wrap the nut with several turns of nichrome or fechral wire and apply voltage to the ends from the car battery. This localized heating will protect sensitive parts from the effects of flame and help significantly loosen the threads..

How to use the nut puller

Bolted joints that have been rusty for ten years or more can be completely unyielding. To separate the parts, the nut was previously hacked or loosened with a chisel. Two notches on different edges are enough, but not on adjacent ones.

Today, a special tool is provided for these purposes. Pullers are similar to box wrenches, but one of the edges has a movable carbide cutter with a screw feed mechanism. It is very simple to use the puller: twisting the cutter close to securely fix it, you need to put the knob on the screw tail and make another 2-3 complete turns. The sharpening angle is specially selected in such a way that the nut deforms, and at the same time its inner diameter increases.

A couple of notches on different sides will be enough for the thread to start turning freely. However, you should be careful: the steel of the cutter is quite fragile, plus there is always the possibility of damage to the bolt thread, which in most cases is undesirable.

If the hairpin boils: learning to work with an extractor

If a bolt is screwed into an internal thread in one of the parts, then heating, annealing and other effects on the connection are very limited. Very often in such cases, the bolt breaks off and a debris remains inside the part..

If a bolt of large diameter (M10 or more) breaks off, and at the same time you can use smaller fasteners for fixing, then it is much more profitable to drill a new hole and make a smaller thread in it. The opposite is also possible: drill the bolt completely with a larger drill and cut the larger thread.

In such operations, you need to be very careful and carefully control the direction of drilling. Especially where a harder steel bolt is surrounded by softer material, such as in the engine block.

If you have a special tool, the chip can be completely unscrewed. It makes sense to use an extractor when the size of a broken bolt is from M6 and above, smaller studs require an almost jewelry approach.

To unscrew the fragment with an extractor, you first need to make a longitudinal hole along its central axis of such a diameter, for which the specific extractor used is designed. Before this, the visible edge of the fragment is ground perpendicularly and punch exactly in the center..

The extractor has a left-hand thread with a slight taper. When screwing it into the body of a bolt or stud, a moment comes when the friction forces in the internal thread become higher than in the external one, and then the boiled debris breaks off and can be relatively easily removed.

When using the extractor, it is necessary that enough “body” remains in the debris, otherwise the cone screw can crush the rest of the stud and jam it even more. It is also very important to adhere exactly to the established diameters of the preparation holes and to use only the appropriately sized extractors..

Ways to Prevent Corrosion on Threads

When you repair the threaded connection, take care that the problem does not reoccur. You can protect threads from corrosion by using greases with neutral acidity or slightly alkaline ones. This class of fuels and lubricants is called conservation, typical examples are graphite grease USSA and “Solidol”.

Environmental protection of the threaded connection will also help. Most alkyd or polyurethane based paints and enamels are suitable for this. You should not use silicone, because its high acidity only contributes to the formation of rust.

Finally, do not forget that some threaded connections need maintenance and tightening. If the connection must remain detachable, it must be periodically (once every 2-3 years) released and lubricated at least with ordinary machine oil.