2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16
A thread is an ornate spiral with a constant pitch applied to a conical or cylindrical surface. It is the main element for connecting two types of fasteners, as well as screw and gear-screw gears. The main parameters of threads on modern fasteners are defined in GOST 11708-82: this is the thread pitch between adjacent turns, the outer and inner diameters of the fastener element, the angle of the top of the thread.
Types of threads on fasteners are divided into:
- internal - applied to nuts, anchor sleeves, couplings, pipes;
- external - located on self-tapping screws, screws, screws, bolts, studs.
There are the following types of threads according to the corresponding GOST:
- metric - a profile in the form of an equilateral triangle (it happens with small, medium and large steps);
- inch - triangular or trapezoidal;
- metric conical - has a triangular profile;
- round - a protrusion of the top of a round shape;
- trapezoidal - ledgetrapezoidal tops;
- thrust - trapezoidal asymmetrical profile;
- modular - trapezoidal profile shape;
- pipe conical and cylindrical (the profile has the form of an inch-sized isosceles triangle with a rounded (or flat-cut) top and coil cavity);
- conical inch - a profile with a flat cut top of a triangular shape.
There are other types of threads such as square and rectangular. They are applied to fasteners by screw-cutting lathes according to individual drawings. Such types of threads do not allow obtaining a high degree of accuracy, therefore they are used quite rarely. There are no GOSTs on them.
Today, for general machine-building applications, the main external and internal threads are considered metric. In the drawings, it is indicated by a capital letter "M" with an indication of the outer diameter in millimeters. Pipe thread types are used to connect various pipes. Their nominal diameter is the inner diameter of the pipes, the outside of which is threaded. In the drawings, it is indicated by a capital letter "G" indicating the internal diameter of the pipe in inches.
The main thread sizes of all types are reference data. They can be found in any machine builder's manual. For metric threads, reference data are described in detail in accordance with GOST 9150-81, 24705-81 and 8724-81. For cylindrical pipe threads, the dimensions are specified in GOST 6357-81.
One of the common fastenerselement with metric thread is a bolt. It is a metal rod with a head at the end. A helical groove is applied along the length of the rod. The purpose of bolts is to connect various parts of mechanisms and structures with a nut. The head of the bolt can be hexagonal and shaped (secret, semicircular, butt, mortgage, terminal).
There are the following types of bolts by purpose:
- furniture - used to connect products in furniture production;
- machine-building - used in the industrial sector;
- ploughshares - designed for coupling machine equipment in the agricultural industry;
- road - used to connect various metal structures and road barriers.
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