SU1574337A1 - Screw tap without chips - Google Patents

Abstract

The invention relates to the processing of metals by pressure, in particular to a chipless tap, and can be used in the preparation of internal threads by cold plastic deformation. The purpose of the invention is to increase the resistance of taps due to a decrease in the specific pressures in the working sections of the deforming faces. In the cross section, the tap has the shape of a polyhedron with deforming edges, on which working areas are located. In the working sections, the angle of the thread coil profile is made variable, decreasing from the center of the section to its edges. On the remaining length of the deforming face, the angle of the profile remains constant, reduced from the nominal value by 2-6 °. When the tap works, the variable angle of the thread profile of the working sections ensures their gradual entry into work and improves the conditions of plastic deformation. This prevents chipping of working areas and increases the resistance of taps. 3 il.

Description

(21) 4388803 / 25-27

(22) 01.02.88

(46) 06/30/90. Bul No. 24

(71) Brno Automobile Plant

(72) C. F. Rickman

(53) 621.771.013 (088.8)

(56) USSR Author's Certificate No. 730427, cl. B 21 N 3/08, 1979.

(54) WITHOUT BAR

(57) The invention relates to the processing of metals by pressure, in particular to a chipless tap, and can be used in the preparation of internal threads by cold plastic deformation. The purpose of the invention is to increase the resistance of taps due to a decrease in the specific pressures in the working sections of the deforming faces. In the cross section, the tap has the shape of a polyhedron with deforming edges, on which working areas are located. In the working sections, the angle of the thread coil profile is made variable, decreasing from the center of the section to its edges. On the remaining length of the deforming face, the angle of the profile remains constant, reduced from the nominal value by 2-6 °. When the tap works, the variable angle of the thread profile of the working sections ensures their gradual entry into work and improves the conditions of plastic deformation. This prevents chipping of working areas and increases the resistance of taps. 3 il.

The invention relates to the processing of metals by pressure and can be used in the preparation of internal threads by cold plastic deformation.

The aim of the invention is to increase the resistance of taps due to a decrease in the specific pressures in the working areas of the deforming faces.

FIG. Figure 1 shows one deforming face of the cross section of the threaded portion of the tap; in fig. 2 is a section A-A in FIG. one; in fig. 3 - section BB in FIG. one.

The tap in cross section on the intake and calibrating parts has deforming faces 1, butted along the thread profile. On the deforming edges there are working sections 2. Within the length of the working section, each deforming edge has a variable angle of the thread coil profile, which decreases from the center of the section to its edges. In the center of the working section, the angle of the thread profile a is equal to the nominal value and working area angle profile of the thread is equal to the angle b. On the remaining length of the deforming face, the angle of the profile remains constant and equal to the angle b. Such an embodiment of the working sections of the deforming edges allows one to obtain them in the form of a gradually expanding and then narrowing wedge (in arc sections). The magnitude of the decrease in the angle of the thread profile is in the range of 2-6 ° or 1-3 ° per side. At an angle less than 2 ° within the length of the working faces, the wedge is practically absent, which does not allow for a reduction in the specific pressures in the contact zone of the metal deformation.

If the magnitude of the change in angle is greater than 6 °, then the change in specific pressure will not be gradual.

The tap works as follows. During the forward run, the working areas of the deforming edges of the intake part begin to be embedded in the metal parts. As the tap advances, the deforming edges of the gage part come into play, which finally form the track 1

four

WITH

with J

fil carving The variable angle of the profile of the working sections of the deforming edges ensures their gradual entry into work and improves the conditions of plastic deformation of the metal, as at the time of introduction of the working sections into the metal, the forces on them increase gradually. During the return stroke, the tap ejects from the machined hole.

An increase in the resistance of taps is associated with a decrease in the specific pressures in the zone of plastic deformation of the metal. Due to the gradual introduction of the working sections of the deforming faces into the work of the expanding wedge, the specific pressures on them do not increase stepwise, but gradually. This prevents the chipping of the working areas of the deforming edges.

Aa

FIG. 2

especially when processing metals with enhanced mechanical properties.

Claims (1)

Claims without a chipless tap containing intake and calibrating parts that have a polyhedron profile in cross section with deforming edges running along the thread profile and working areas on them, that, in order to increase durability by decreasing the specific pressure, the angle of the thread profile of the working sections is made decreasing from their center to the edges, the angle of the thread profile in the center of the working areas being equal to the nominal value, and over the remaining length of the deforming faces, 2-6 ° less than the nominal value. B - B Fig.Z