In modern manufacturing uses many design elements, each of which performs a specific function final product, often very important.Therefore, one of the objectives in the design and manufacture of complex composite structures becomes reliable fixation of parts to each other.
purpose of using bolt
There are many options for connecting two products, such as welding, soldering, bonding, use of rivets.However, they have one common and quite a significant drawback - they are all one-piece.More precisely, the split, but to separate their parts have to deform to cut and so on.
much more convenient to use as a fastener fitting, picking up pre-class strength bolts, depending on the load rests with the unit.
thread is used in virtually all designs that are a little harder to ordinary teaspoon.Imagine a car that no one screw.Why are there cars - children's toys, strength class structure which is much lower still can not do without threaded elements.
Benefits threaded connection
Despite the fact that sometimes the big torque does not allow some time free to unscrew the nut, bolt, still has a number of advantages over other methods of fastening:
- High reliability connection provides universal profile metric or any other thread.Profile developed thanks to numerous studies, because withstand heavy loads and is protected from self (although it will have to choose the correct torque).
- Ease of installation and dismantling structures.Provided it using unified service tools - keys, wrenches, which is not true, for example, welded or riveted connections.
- ability to create large axial and transverse loads.Bolt strength is calculated in both the longitudinal and transverse direction.Modern materials and technologies make it possible to reduce the amount of the fixture and reduce its size.
- low cost, especially when compared to the cost of the purchase of welding materials and works.
Among the shortcomings of the connection - the concentration of stress in the thread root.Therefore, for a particular type of construction is necessary to choose the strength class of the bolt according to the applied load.Also, to ensure the reliability of threaded connection it is worth remembering the use of the locking means, such as spring washers or lock nuts.
Types threaded connection
To screw connection, there must be one detail to make an internal thread, and the second - the outside.Depending on the design features can be used three varieties:
1. Screw connection.In this case the role of the nut (female screw parts) performs part of the node.It is first drilled hole.A thread is then applied.For other parts applied with a smooth circular hole, after which a screw is drawn.
2. Bolt.There is much simpler and more reliable: in both parts joined smooth drilled hole, bolt inserted therein, and on the reverse side - the nut.
3. On the heels, one end of which is screwed into the detail of the node, and the second - the nut is screwed.
Strength class of the bolt
As noted above, the fasteners must be well matched.There is no sense in a normal frame shelf service tools to use parts made of stainless steel.At the same time, in some flanged joints (such as tightening components of multi-ton steel structures) is required to use materials with improved mechanical properties.Generally
strength class bolts (GOST 1759.4-87) - is a set of mechanical characteristics, which also includes a temporary resistance, the border point, the relative magnitude of the elongation after fracture, hardness of the material, and in some cases even toughness.As a rule, to refer to this parameter uses two numbers separated by a dot.The first of them, after multiplication by 10 indicates the minimum value of tensile strength, and the second, also at 10X magnification shows the proportion obtained by dividing the yield strength of the material on the tensile strength.The product of these two figures also point to the value of the minimum yield strength.Strength class of the bolt is contained in its labeling, which is as follows: M12h1,25h60.58 where 58 - the same two-digit number.
Tightening
order to securely hold the screw connection elements of the construction, it is necessary to pay close attention to the effort (time) tightening.So, imagine a situation where an inexperienced "car mechanic" for the first time fall under the hood of your own brand-new car and trying as hard as possible to clamp nut or screw.All this can result in the first case, just uncomfortable chisel work, and in the second - by drilling holes in the hull.It is due to incorrectly matched torque.The experienced car mechanics, repairmen and just have a "built-in hand" dynamometer.But the newcomer is best to use a torque wrench or pneumatic impact wrenches, which are tuned to a specific torque.
How to unscrew the "complex" bolt
Let's tighten it worked out.But time passes, and you need to unscrew the fasteners again.Due to corrosion make it sometimes is not very easy, and the high strength bolt class does not save it from destruction.So you should keep in mind a few simple ways that facilitate the unwinding:
1. To begin to use the "VeDeshkoy."The composition dissolves the layer of rust.
2. Gently tap the nut with a hammer to break the rust in the thread.
3. You can try to crank up a few degrees in the direction of tightening the nut and then unscrew.
It is important not to rush, as they are likely to stay with the nut or bolt head in the key.
