Characteristics of standard threads 

Metric thread is the most common in technology. Its profile is formed by an equilateral triangle with an angle at the apex of 60 . The vertices of the profile are flat-cut, the depressions can be flat-cut or rounded to increase the strength of the thread. Metric threads come with a large and small pitch. A thread with a small pitch is used when connecting thin-walled parts, limiting the screwing length, and also when increased strength and reliability of the connection are required.

To designate a metric thread, only a small pitch is included, a large pitch is not indicated.

Trapezoidal thread is a profile in the form of an equilateral trapezoid with an angle at the apex of 30 . It is used on screws to convert rotational motion into translational motion under significant forces.

Buttress thread – used on screws that transmit a one-sided directed force (press, jack, etc.). The efficiency of the buttress thread is greater than that of the trapezoidal one.

The thread profile is an unequal trapezoid with an angle at the vertices of 33° and 3°. The recesses of the external thread are rounded.

Square thread – used to convert rotational motion into translational motion in connections where there should be no self-unscrewing under the action of a relatively small applied load. Due to the fact that the thread profile is not standardized, the drawing provides all the data necessary for its manufacture: two diameters (outer and inner), pitch and thread thickness.