RU2542217C2 - Tap - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metal processing, particularly, to cutting of female thread. Tap comprises flutes and clearance grooves. At least one clearance groove has an angular shift to increase the width of at least one flute.

EFFECT: higher tap durability and thread quality.

2 dwg

Description

The invention relates to metal processing, namely to the processing of internal threads.

Known chipless tap [Metal cutting tools: Uch. for universities. Sakharov G.N. et al., M.: Mechanical Engineering, 1989 .-- 328 p. - p. 175, fig. 3.9]. In such taps, instead of chip grooves, the working part in cross section has a polyhedron, on the intake cone the thread is polished onto the cone, there is no backing. In the process of thread formation, extrusion occurs along the entire profile. Therefore, such a tap has limited use, namely in the processing of easily machined metals and alloys, characterized by a coefficient of elongation δ> 10-12%.

Taps with chip grooves are also known [ibid., P. 174]. The chip grooves in them serve to accommodate the cut chips and are performed with a uniform circumferential pitch. The number of grooves is taken equal to 2-6 when changing the outer diameter I within 2-52 mm

During the processing of corrosion-resistant steels and alloys and other materials, during the cutting of which drainage chips are formed, the chips clog the grooves, the cutting fluid is difficult to enter the cutting zone, the cutting torque increases, the quality of the thread worsens, the tool jams and breaks. An increase in the volume of chip grooves will lead to a decrease in the diameter of the core, therefore, to a decrease in stiffness and a decrease in tool life.

The aim of the invention is to increase the tool life, the quality of the treated surfaces.

This goal is achieved by the fact that at a tap with chip grooves, at least one chip groove is made with an angular shift. This technical solution meets the criterion of "novelty", since the prototype has no signs set forth in the characterizing part of the claims. The authors are not aware of other technical solutions, including taps, in which at least one chip groove is made with an angular shift and the feathers have different widths. Therefore, we can conclude that the proposed solution meets the criterion of "significant differences".

Figure 1 shows the shape of the teeth of a standard taps with three feathers.

The tap contains three chip grooves I, II, III, respectively, three feathers I _n , II _n , III _n . For a standard tap, the clearance angle is obtained by backfilling the archimedean spiral AE. The amount of backing EL is determined by the well-known formula:

$$EL=\frac{\pi d}{z}tg\alpha ,(\mathrm{one})$$

where d is the diameter of the tap, α is the size of the rear sharpening angle, z is the number of feathers.

Figure 2 shows a cross section of the proposed tap with three feathers.

One chip groove, in our case I, is made with an angular shift θ clockwise while maintaining the core diameter d _c . In this case, the volume of the chip grooves does not change, the width of the pen III _n increases. The backing of the teeth on the rear surface of the proposed tap is made like a conventional standard tap.

The execution of the chip groove I with an angular shift θ clockwise leads to a mixing of the cutting edge from point A to point C, which leads to a decrease in the thickness of the cutting teeth of the first feather I by BC

$$BC=\frac{\pi d}{360}\theta tg\alpha (2)$$

The cut thickness of the teeth of the third feather a _IIIn tap is determined by the well-known formula

$$a_{IIIn}=\frac{P}{z}tg\varphi (3)$$

where P is the thread pitch, z is the number of feathers, respectively, of the chip grooves, φ is the angle of the tap intake cone.

The thickness of the cut layer by the teeth of the first feather In will be less by BC than a_IIIn, those.

$$a_{In}=a_{IIIn}-\frac{\pi d}{360}\theta tg\alpha =\frac{P}{z}tg\varphi -\frac{\pi d}{360}\theta tg\alpha (\mathrm{four})$$

The thickness of the cut-off layer by the teeth of the second feather II _n, respectively, will be BC greater than a _IIIn i.e.

$$a_{IIn}=\frac{P}{z}tg\varphi +\frac{\pi d}{360}\theta tg\alpha (5)$$

The tap works as follows. In the process of cutting, the teeth of different feathers work with different thicknesses of the cut. Due to the heterogeneity of the material being processed, the presence of hard and soft inclusions in it, and the different thickness of the cut with different teeth, the tap will make forced torsional vibrations during thread processing. Since the friction force decreases with increasing speed, these oscillations will help to reduce friction in the cutting zone, the supply of cutting fluid is facilitated, the formation and removal of chips is facilitated (element chips are formed), and its sticking to cutting edges is eliminated. All this significantly reduces the friction moment and, accordingly, the magnitude of the torque. As a result, the quality of the machined surfaces improves, and the tool life increases. In addition, the formation of elemental shavings makes it possible to slightly reduce the volume of the chip grooves by increasing the core diameter d _c . This will increase the rigidity of the tool, respectively, tool life and thread quality.

Literature

Metal-cutting tools: Uch. for universities. Sakharov G.N. et al., Moscow: Mashinostroenie, 1989. - 328 p. - p. 175, fig. 3.9.

Claims (1)

A tap for processing internal threads containing feathers and chip grooves, characterized in that at least one chip groove is made with an angular shift, providing an increase in the width of at least one feather.

Images