Threaded connections depend on the outer and inner surface of the arrangement. They are internal, external, conical and cylindrical. They differ in the cross-section and profile of the part: round, rectangular, resistant, trapezoidal. Appointment is running or fixing.
The fastener has a triangular profile and is divided into two groups: inch and metric.
The threaded connection inch is measured in inches (from this and the name), the pitch is 25.4 mm. It is characterized by the number of threads of a helical line per inch of the cut part.
Inch is used to connect pipes (called "pipe threads"). Also used for cutting on spare parts of various equipment. In machines that are made in our time, inch thread is not used. Standards are developed for metric, so design is carried out under this standard.
Threaded connections with a threaded thread are used at high loads. Trapezoidal fasteners serve as fasteners for the transmission of movement (running screws) and forces, but do not rigidly fasten parts. For reinforcement, round thread is used, in machines it is used extremely rarely.
With a triangular profile, threaded connections are the most reliable, even with
the same diameter. Resistant is less durable. Trapezoidal thread will be even less reliable. The weakest is rectangular. Thanks to smooth rounding, the round has high dynamic strength.
Threaded connections are divided into groups: screw, combination, bolt and stud.
The simplest connections consist of a nut and a screw.
In order to prevent self-loosening in the joints, locking parts are used that soften vibration and shock load, reduce friction.
The guides provide many ways to stop yourself from unscrewing.
Threaded connections for the car are made using bolts made of carbon metal. In fasteners that require increased reliability and strength, alloyed chrome steel is used. At the moment of tightening the threaded connections, a dynamic key is used (the moments of force loading are normalized in it). Such keys are used in mechanisms where the strength of the connection is strictly defined in the technical documentation.
The threaded connections are first clamped, then loosened a little and tightened again. This controls the correct clamping force.
The calculation of threaded connections is carried out in order to determine the voltage that occurs in the connection. You also need to calculate the safety margin for the bolts used.
The calculation is performed on the elements:
- without nut and with nut;
- with eccentric and concentric loads;
- with fastening by a hairpin;
- the contact zone is determined by the geometry of the thread;
- if there are many sections of cylindrical shafts;
- with many plates.
The calculations use only statistical loads.
Threaded connections are good in that they can always be disassembled without damaging the parts themselves.