Threaded connections and their types

The threaded connections from the outer and inner surfaces of the arrangement hang. They are internal, external, conical and cylindrical. The cross-section and the profile of the part differ: round, rectangular, thrust, trapezoidal. The appointment is running or fastening.

Mounting has a triangular profile and is divided into two groups: inch and metric.

The inch threaded connection is measured in inches (hence the name), the pitch is 25.4 mm. Characterized by the number of threads of the screw-like line per inch of the cut piece.

Inch are used to connect pipes (called "pipe threads"). Also used for cutting on spare parts of various equipment. In machines that are manufactured in our time, inch carving is not used. The standards are designed for metric, so the design is carried out under this standard.

Threaded connections with thrust threads are used for heavy loads. The trapezoidal bolts serve as a fastener for the transfer of motion (propellers) and forces, but do not rigidly fasten the parts. For the reinforcement used round thread, in machines it is used extremely rarely.

With a triangular profile, threaded connections are the most reliable, even with Of the same diameter. Resistant is less durable. Even less reliable thread will be trapezoidal, the weakest - rectangular. Due to the smooth rounding, the round has a high dynamic strength.

Threaded joints are divided into groups: screw, combined, bolt and hairpin.

The simplest joints consist of a nut and a screw.

In order to avoid self-loosening in the joints, detachable parts are used that soften vibration and shock loading, reduce friction.

There are many ways of stopping from self-unscrewing in the manuals.

Threaded connections for the car are made with bolts made of carbonaceous metal. In the fasteners, which require increased reliability and durability, alloyed chromium steel is used. At the tightening torque of the screwed connections, a dynamic key is used (stress load moments are normalized). Such keys are used in mechanisms where the strength of the connection is strictly defined in the technical documentation.

Screw connections are first clamped, then loosen a little and then tighten again. So the correctness of the clamping force is controlled.

Calculation of threaded joints is performed to determine the voltage that occurs in the connection. Also you need to calculate the safety factor for the bolts used.

The calculation is carried out according to the elements:

- without nut and with nut;

- with eccentric and concentric loads;

- with a pin;

- the contact zone is determined by the geometry of the thread;

- if many parts of the shafts are cylindrical;

- with many plates.

In the calculations, only statistical loads are used.

Threaded connections are good because they can always be disassembled without damaging the parts themselves.