How to fix a bolt in a thread. Loosening bolts and threaded fasteners from vibration. Extreme Sports
Threaded connections are quite reliable and efficient. They are considered one of the most common and cost-effective. However, when exposed to vibration, there is a possibility of weakening them. This can often be seen in the example of nuts that loosen randomly during operation of various devices. Therefore, methods have been developed that can reduce this effect or completely eliminate it.
Ways to avoid loosening the nut
1. Using a washer. This method is one of the most common. It is used in the manufacture of household appliances and some types of industrial equipment. It does not have a high degree of reliability and is protected from arbitrary unwinding. A soft metal washer is placed on the thread, and then the nut is tightened, squeezing it out.
2. Washer and Grover. A more reliable method practiced by the transport industry. Protects the threaded connection from arbitrary unwinding even in the presence of slight vibration. First, a regular washer is put on the thread, and then a groover. After this, tighten the nut. The Grover here serves as a kind of spring, creating tension that prevents unwinding.
3. Special nut with lock. The method using a special nut cannot be called the most effective. However, it takes place in world practice and is used in some types of production.
4. Using thread locker. The composition is applied to the place where the nut will be located, after which it is put on the thread. This is a fairly effective way to prevent random unscrewing, but its effectiveness is affected by changes in temperature, high humidity and exposure to active substances. Therefore, its scope is limited.
5. Use of two or more nuts. One of the most reliable methods. Two nuts are screwed onto the thread at once. After clamping the first, the second is tightened separately, holding the first in its original position and even trying to unscrew it a little.
6. Fixation with a cotter pin. This is the most reliable method, able to withstand almost any external influence and strong vibration. It is used in particularly critical areas. The nut is fully tightened. Then, using a drill and a thin drill bit, a hole is made that pierces it along with the bolt. A pin is inserted into the resulting hole, the antennae of which are unbent, preventing it from falling out. Such a nut can be torn off only with a very strong rotational force in the direction of the thread.
The term “anaerobic” came to technology from biology. This is the name given to microbes that prefer to exist and develop in the absence of oxygen. By the way, this is why all the tubes with anaerobic compounds we purchased are sold half-empty: they need air for storage! And when it enters a limited volume without air flow (for example, into a threaded gap), the composition quickly polymerizes, that is, hardens. Such means are used not only for locking threaded connections, but also for sealing welds, sealing flanges, etc.
Why did you need a replacement for growers and other ancient remedies? The class of thread accuracy has increased, optimal tightening torques are used in production, and bolts with an increased bearing surface are used. Therefore, the old-fashioned methods have practically died out: it is almost impossible to find a grower on a modern machine. But fixing compounds are used more and more often - when attaching brake calipers, camshaft pulleys, in gearboxes, and steering mechanisms.
To test anaerobic clamps, we prepared fastening elements with M10×1.25 threads - bolts and nuts. For each test product, we took it together with a nut screwed onto it, having previously cleaned and degreased them, treated the threaded part of the bolt with a fixative, after which a second nut was screwed onto it with a small fixed tightening torque (0.1 N m). A small tightening torque value is chosen so that it does not affect the final measurement, the purpose of which is to determine the loosening torque on an untightened threaded connection. In other words, we tested exclusively the effect of the clamps, and not our own muscles. Each of the threaded connections was numbered according to the conventional number of the fastener with which it was processed.
Manufacturers declare the abilities of drugs in different ways, but color gradation is mainly used. Red color suggests that we have before us a product with the highest possible capabilities - heat-resistant and even “one-piece”. Blue color indicates more modest fixing capabilities - the connection will remain detachable. There are also very weak drugs - green.
We do not recommend focusing only on color: look for exact information about the purpose of the product either on the packaging or in the description. However, not everything is transparent here either. For example, from what moment the connection is declared “inseparable” is not clear from the descriptions. Some manufacturers indicate the moment of resistance that their product provides, but do not talk about the corresponding size of the threaded connection. And this is important, because a tiny screw from glasses requires much less torque to unscrew than a huge hub nut. There is an opinion among people that “you can assemble it with a strong latch and that’s it.” But that's not true. Strong clamps can really kill small fasteners, but no sealant will turn even medium-sized connections into a monolith, for example, those with M10...M14 threads.
That is why we decided to test all purchased drugs using a single method. After 24 hours at room temperature, each connection was clamped in turn on a stationary frame so that the head of the verified torque wrench captured only the upper nut, which had to be unscrewed. The initial torque set on the key is 5 Nm, which is less than 10% of the maximum tightening torque of such fasteners (on M10 connections in cars the torque reaches 80 Nm). If the connection could withstand the specified force, the moment was successively increased in increments of 5 Nm. The higher the moment at which the threaded connection began to unwind, the higher the quality of the fastener being tested.
The final assessment was adjusted taking into account the manufacturer’s promises: those products whose descriptions did not promise anything received a lenient assessment, while powerful “red” ones, which frankly did not live up to the stated indicators, were subjected to harsher criticism. At the same time, the viscosity of the drugs was assessed. They differ noticeably in this parameter, but we did not find a direct relationship between viscosity and professional suitability of the product.
By the way, the clamps protect against oxidation and seal the connection. And sometimes the best fixative is rust. Along with anaerobic fixatives, we decided to test other methods of stopping joints - just for comparison. About them - a little lower.
| approximate price 70 rub. The sealant, liquid as water, gave in at the first test. However, his instructions did not promise anything specific. | approximate price 190 rub. The removable American fastener removed itself at the very first step of testing - with a minimum applied force of 5 Nm. | approximate price 190 rub. The rather thin composition successfully withstood the applied torque of 5 Nm, but gave up at the next threshold - 10 Nm. The result is weak, but the vast majority of drugs failed even this. |
| approximate price 150 rub. The rather thick product promised to last until 35 Nm. It's hard to say what the manufacturers had in mind, but it didn't take more than 5 Nm to unscrew our bolts and nuts. Fail. | approximate price 150 rub. The thick sealant promised to last up to 35 Nm, but in practice it gave up at 10 Nm. Better than many, but essentially it doesn’t matter. | approximate price 150 rub. The product promised to last until 17 Nm, regardless of the thread diameter. And the recommended range of application for thread diameter is not indicated. The result is negative: the connection easily untwisted already at a modest 5 Nm. Fail. |
| approximate price 290 rub. The product of medium consistency withstood a torque of 5 Nm, but gave up at the second step. Well, most couldn't do that either. | approximate price 390 rub. The rather fluid product did not show itself in any way, allowing the nut to unscrew on the first try. But there were no specific promises. | approximate price 310 rub. An expensive American product of modest volume showed nothing but ambition. The medium fluidity fastener gave in at the first contact with the torque wrench. What about the definition of “high-strength”? Failure! |
| approximate price 105 rub. The Russian product is a substance of medium viscosity. The tests ended very quickly: an applied torque of 5 Nm instantly moved the nut out of place. However, the manufacturer did not make any specific promises. | approximate price 105 rub. In practice, the rather thick composition behaved just as poorly as its colleague number 10: on the first try, the nut easily came loose. And this is called “one-piece”? Fail. | approximate price 190 rub. Not the thickest product, prone to dripping, won the competition by a large margin over its competitors! It was possible to move the nut fixed by him only by applying a torque of 30 Nm. Great! |
| approximate price 190 rub. The thin crew refused to fulfill their duties, giving up at the very first stage of inspection. We will assume that this means “medium strength”. | approximate price 160 rub. How to understand the contradictory wording “up to 20 mm or more”? For any thread? It sounds optimistic, and the torque is promised to be at least 35 Nm. But there was no result - the product of heterogeneous consistency gave up on the first step, at the mere sight of the key. Fail. | approximate price 160 rub. The product promised to fix fasteners up to a torque of 35 Nm, but things didn’t work out from the very beginning. The bottle with the screw cap leaked immediately - sealed products are better! The liquid of medium consistency, after the required exposure, gave up at the first touch of the key. Fail. |
| approximate price 160 rub. The thin product declared its readiness to last up to 17 Nm. It didn’t work: the connection came loose at a torque of less than 10 Nm. Our rating: satisfactory. | approximate price 300 rub. This product is not designed for a thread diameter of 10 mm, but we wanted to try it - what if? However, no “suddenly” happened: the nut came loose on the first try. But we won’t find fault: the product is stated to be weak. | approximate price 285 rub. The thick product loosened its grip only at a torque of 25 Nm. This is the second result in our sample. Very good! |
| approximate price 225 rub. During testing, the rather thick American product gave up almost instantly - already at a torque of 5 Nm. But the drug did not promise anything special. | approximate price 220 rub. The sealant of medium thickness gave way at a minimum moment. And why was it necessary to announce high durability? Fail. | approximate price 260 rub. In terms of fluidity, this product is identical to water. And the effect is the same as water. On the first try, the nut immediately moved out of place. But the manufacturer didn’t say anything special. |
Who recorded who?
Well what can I say? The overall impression is quite pathetic. Of the twenty-one drugs tested, only six were able to withstand a modest initial torque of 5 Nm, and only two of the remaining ones advanced beyond 10 Nm.
However, the Teflon nut and lock washer also failed at the first stage. And nail polish turned out to be unsuitable for serious matters. The extra-grade glue left over from previous examinations lasted a little longer - it gave in under a load of 10 Nm. And the most curious thing is that at a torque of 30 Nm... the cotter pin was cut off! It would seem that the metal part would last longer, but it only repeated the results of the best drug we tested.
Let this be a purely technical note. Separately, I wrote about a funny story that happened due to - I recommend you read it. There is only technical information here, albeit a little. The knowledge gained from the note will be able to protect you from the inappropriate use of such a special liquid as a thread locker.
What types of clamps are there and on what principle do they work?
Thread lockers are quite dangerous liquids. Incorrect use of thread locker is guaranteed to lead to undesirable consequences.
Thread lockers come in red and blue (green). They differ in the principle of unscrewing:
- Red (one-piece) ones must be heated to a high temperature; without this, it will not be possible to unscrew the bolt with such a lock. Withstands higher temperatures. They are usually used on rotating and high-temperature components (for example, brakes or a bolt securing the main pulley to the crankshaft).
- The blue ones (detachable) are unscrewed with great force. Used on low-temperature units where the likelihood of unscrewing is not high. As a rule, they are protected from unscrewing when exposed to vibration (for example, attaching the bracket directly to the engine).
The classification does not always coincide with the color, so the main criterion is detachable/one-piece. Please also note that recently, along with detachability, clamps with varying degrees of fixation have also begun to be produced, while remaining detachable or non-detachable.
The operating principle is simple. A liquid is applied to the surface of the bolt, which, when dried, bonds the two metal surfaces. A primitive thread locker can be ordinary nail polish. But it should only be used where unscrewing is not critical. In critical assemblies, use only a specialized lock. Its cost is not high. Maximum 150 rubles per tube, which is enough for a large number of repairs.
How to apply
First, you need to be sure that the bolt in question simply requires the application of thread locker. To find out, you need to find the repair manual for your car and read it. Typically this information is written in the same section as the tightening torques.
If you are confident, then open the tube with the fixative and apply a strip of about 5 mm (usually one drop) to the thread, in the place of the bolt where the nut will be located. When you tighten the bolt, the fastener will distribute itself over the contacting surface.
How to unscrew
The blue lock should unscrew without problems. In extreme cases, you can slightly heat the part, but in practice this rarely happens.
It's often worth some effort with the red lock. The first problem is to recognize the presence of the red fixative. If you know that red thread locker is applied to any components that need to be repaired, and you take the car to a repair shop, warn the technicians so that they do not inadvertently break the head of a nut or bolt. Usually this is recognized by the fact of unscrewing. Heating the part with a gas burner helps a lot in dealing with the red retainer. The danger here is that there is rarely anything plastic near the heated part. To avoid melting anything, make a screen of asbestos, or at least tin, so that direct flame does not reach beyond the heated part. And make sure there is nothing plastic adjacent to the heated part. When the part has heated up, it is necessary to quickly unscrew the bolt, since when it cools down, the red lock may seize again.
Good luck with the renovation.
How to fix a threaded connection and lock the nut so that it does not unscrew due to vibration? How to fix and lock a screw or bolt? Vibration resistance of threaded fastening. Vibration resistance (10+)
Fixing the threaded connection - Continued
Glue
Glue or a special fixing compound is applied to the internal and external threads in the place where they will be combined. After drying, the connection is locked. For such fixation, you can use glue that meets the following requirements: (1) It glues the material from which the bolt and nut are made (this can be steel, bronze, fluoroplastic, etc.) (2) It is quite elastic in the dried state and vibration resistant. (3) It is resistant to the environment in which it is intended to be used. For example, it is water resistant if the connection is in water. (4) It dries quickly. It should be remembered that under carving conditions, one-component adhesive rises at least four times slower than under standard conditions, so the instructions for drying time should be multiplied by four, or better yet by six for a margin. If the glue dries slowly, the work risks taking longer. For example, PVA in carvings takes a week to dry. Two-component adhesive (with hardener) cures for a nominal time.
I use the following glues and varnishes:
- Moment glue or rubber glue, if the connection will not be exposed to oils, solvents or their vapors, or sunlight.
- Any universal elastic glue "Liquid nails".
- Poxypol.
- Plumbing glue.
- Universal superglue.
- Primer GF-021 or Otex, if the connection will not be subjected to too much stress.
When choosing glue, consider the dimensions of the parts to be joined. For small parts you need liquid adhesives, such as superglue or Moment. For very quick fixation, you can use hot-melt adhesive, applying it with a hot-melt gun.
Flaws. This connection is quite difficult to disassemble. Sometimes the glue sets so much that it takes a lot of effort to unscrew it. But it is enough to provide a small initial offset. Then the process goes easily.
I like this method because it allows me to assemble threaded connections almost by hand, without tools. While the glue is not dry, it serves as an excellent lubricant and allows you to tighten without effort.
Teflon nut or insert
Inside the nut, a Teflon film is applied to the thread or part of it, or a winding is used - the external thread (bolt) is wrapped with a thin Teflon thread. Once tightened, Teflon creates increased friction and prevents vibration from loosening the connection. With the help of winding, you can fix almost any connection.
Flaws. The Teflon nut is disposable. After unscrewing, it must be replaced. The winding is also disposable. After disassembly, the remnants of the winding must be removed, and a new one must be wound before reassembly.
Common combinations
None of the options provide a 100% guarantee. Even the most reliable method - a cotter pin - can fail. The cotter pin may shear (break and fall out). Therefore, in particularly critical places, the described methods can be combined. You can put a groover between the nut and the locknut, glue a Teflon winding or nut, apply glue to the nut and locknut, etc.
For a threaded connection located in oily liquids (oil, gasoline, kerosene, diesel fuel...) and subject to vibration, only a cotter pin is suitable. All other options are unreliable. In industrial conditions, the reliability of other types of connections can still be ensured, but not in a homemade version.
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It doesn't matter that you have a bicycle, car, furniture, or other thing. But you definitely had a situation where the nut unscrewed on its own. What needs to be done to prevent the nut from unscrewing? You will learn more about this in the training video lesson.
You can use a traditional nut and bolt, but it won't prevent you from coming loose. Using a torque wrench, we tighten the nut by hand, but with high vibrations it will begin to unscrew. To hold it, we need to tighten another lock nut on top. Using a lock nut we can stop the unwinding of a regular nut, but this does not give a 100% guarantee. It is a disposable product.
You can use a traditional Grover washer, it is disposable and can be unscrewed by vibration. It is possible to replace a regular nut with a nut with a flange, which has a wide bearing surface and special notches. They dig into the support pad, but even a nut with a flange does not give us a 100% guarantee.
Serrated washers
One of the most popular and inexpensive solutions is a toothed washer. It has reliable contact with the entire surface and a low price. The main problem that arises is that you can over-tighten and thereby smooth out the teeth. Thus, they turn into a regular flat washer.
The toothed washer can only be used up to the specified torque. A very important point when using it is not to overtighten the nut and thereby flatten the washer. The low price of toothed washers will help solve local loosening of the nut. Only two options will give us a 100% guarantee.
Wedge washer
A wedge washer is a system consisting of two washers. These washers are used in pairs and tightened with the required tightening torque. The trick is that the angle of the internal wedges is higher than the helix angle of the thread. As a result, spontaneous unscrewing becomes impossible.
In order to unscrew the nut, we will need to apply more force than when tightening it. The wedge washer provides a 100% guarantee against spontaneous unscrewing.
Anaerobic thread lockers
Another reliable and convenient way to fix a nut is to use an anaerobic thread locker. To do this, we need to apply liquid to the thread where the nut will be. It is quite flowing and easily spreads along the bolt.
We screw the nut onto the bolt and wait, nothing else needs to be done. After some time, the retainer will harden and the structure will not be dismountable. In order to unscrew it, we will need to heat or apply more force using the key.
We hope this video lesson was useful and interesting. Write your comments, ask questions, we will be happy to answer. Recommend to your friends and acquaintances.