RU2493952C1 - Method of drill grinding - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: method relates to drill rake grinding and comprises positioning the drill so that its cutting edge is located perpendicular to grinder rotational axis to grind the drill by displacing it relative to grinding tool along cutting edge, starting from its periphery. To condition drill wear along cutting edge by distribution of normal face angles at drill positioning drill cutting edge is located at the distance equal to 0.01-0.45 of drill diameter. Drill axis is set at the angle to grinding tool rotational axis to be defined from cited relationship. Note here that grinding is performed by coordinated drill turn around its cutting edge, drill displacement along cutting edge over its entire length and drill displacement along grinding tool rotational axis. Note also that drill cutting edge is placed at termination of grinding at the distance equal to 0.01-0.45 of drill diameter. Direct profile grinding wheel is used as grinding tool.

EFFECT: surfacing of drill wear along cutting edge.

7 dwg, 1 tbl

Description

The invention relates to the field of machine tools, in particular for the manufacture of metal cutting tools, and can be used mainly when sharpening spiral drills.

The prior art method for grinding the front surface, in which on the front surface of the drill holes are ground at a certain length of the cutting edge, reducing the rake angle to increase the strength of the peripheral sections of the edge (Eremeeva N.M. Drills / Ed. By M.T. Galey. - M: Mashgiz, 1959, p. 31).

The disadvantage of this method is that the value of the rake angle in the central sections of the cutting edge does not change and remains negative, which leads to a worsening of the cutting conditions.

The closest technical solution to the claimed invention is a method known from the prior art for grinding drill bits on the front surface with a shaped grinding wheel, in which the cutting edge of the drill is crossed with the axis of the grinding wheel at a right angle, and then the drill is informed of movement along the cutting edge (Handbook of a designer-toolmaker: Under the general editorship of V.I. Baranchikov. - M .: mechanical engineering, 1994, p. 211).

The disadvantage of the prior art method is the constancy of the normal rake angle along the cutting edge. At the same time, it is known that the wear of the drill along the length of the cutting edge is uneven and depends on the distribution of the normal rake angle along the cutting edge. In this case, the optimal value of the normal rake angle depends on the cutting conditions and varies along the cutting edge. Uneven wear along the cutting edge leads to a decrease in drill resistance.

The technical result, the solution of which the claimed invention is directed, is to ensure alignment of wear of the drill by controlling during sharpening the distribution of normal rake angles along the cutting edge.

This technical result is achieved by the fact that in the method of sharpening drills on the front surface, which consists in positioning the drill so that its cutting edge is perpendicular to the axis of rotation of the grinding tool, followed by sharpening the drill by moving it relative to the grinding tool along the cutting edge of the drill, starting from its periphery, according to the invention, when positioning the drill, its cutting edge is positioned from the end of the grinding tool angle "a", which is (0.01-0.45) d, where d is the diameter of the drill, and the drill is set so that its axis of rotation is at an angle θ to the axis of rotation of the grinding tool, while the angle θ is determined from the following ratios:

$$\theta =\arccos (\sin \phi \cdot \cos (\gamma +\arccos \sqrt{\frac{d^2-\mathrm{four}{r}_C^2}{d^2-\mathrm{four}{r}_C^2\cdot {\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="00000006.png,00000007.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\phi }}))$$

Where:

φ is the drill angle in plan;

γ is the specified normal rake angle at the periphery of the drill;

d is the diameter of the drill;

r _c is the radius of the core of the drill,

however, sharpening is carried out: by means of a coordinated rotation of the drill around its cutting edge; moving the drill along its cutting edge over its entire length; movement of the drill along the axis of rotation of the grinding tool, and, at the end of sharpening, the cutting edge of the drill is positioned from the end of the grinding tool at a distance “b” of (0.01-0.45) d, where d is the diameter of the drill, and use as a grinding tool straight grinding wheel.

The invention is illustrated by drawings, where:

- figure 1 shows the positioning of the drill relative to the grinding tool,

- figure 2 shows the position of the drill at the beginning of sharpening,

- figure 3 shows a view along arrow A at the beginning of sharpening,

- figure 4 shows a view along arrow B at the beginning of sharpening,

- figure 5 shows the position of the drill at the end of sharpening,

- Fig.6 shows a view along arrow A at the end of sharpening,

- Fig.7 shows a view along arrow B at the end of sharpening,

where respectively are depicted:

1 - drill;

2 - grinding tool;

3 - cutting edge of the drill;

4 - axis of rotation of the grinding tool;

5 - axis of rotation of the drill.

The method of sharpening drills is as follows.

Before sharpening, the drill 1 is positioned relative to the grinding tool 2 as follows. The cutting edge 3 of the drill 1 is placed perpendicular to the axis of rotation 4 of the grinding tool 2 at a distance "a" from the end of the grinding tool 2, comprising (0.01-0.45) d, where d is the diameter of the drill. The drill 1 is set so that its axis of rotation 5 is at an angle 6 to the axis of rotation 4 of the grinding tool 2, while the angle 9 is determined from the following ratio:

$$\theta =\arccos (\sin \phi \cdot \cos (\gamma +\arccos \sqrt{\frac{d^2-\mathrm{four}{r}_C^2}{d^2-\mathrm{four}{r}_C^2\cdot {\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="00000006.png,00000007.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\phi }}))$$

Where:

φ - drill angle in plan

γ is the specified normal rake angle on the periphery of the drill,

d is the diameter of the drill,

r _c is the radius of the core of the drill.

The value of the angle θ is chosen such that it provides for sharpening the drill 1 a predetermined normal rake angle γ at the periphery of the drill 1.

Then the grinding tool 2 is informed of the rotation and sharpening the drill 1 by means of simultaneous and coordinated actions: turning the drill 1 around its cutting edge 3; moving the drill 1 along its cutting edge 3 over its entire length, starting from the periphery of the cutting edge 3; the movement of the drill 1 along the axis of rotation 4 of the grinding tool 2. At the end of sharpening, the cutting edge 3 of the drill 1 is positioned from the end of the grinding tool 2 at a distance "b" of (9.01-9.45) d, where d is the diameter of the drill.

As a grinding tool, a straight profile grinding wheel is used.

At the production site of GOU FSBEI HPE MSTU "STANKIN" the tests of the proposed method were carried out, namely, when sharpening drills with a diameter of d = 30 mm on the front surface, with an angle in the plane of φ = 59 °, a normal front angle at the periphery of γ = 39 °, s the radius of the core drill r _c = 3 mm, designed for machining holes in steel billets.

Before sharpening the drill 1 was positioned relative to the grinding tool 2 as follows. The cutting edge 3 of the drill 1 was placed perpendicular to the axis of rotation 4 of the grinding tool 2 at a distance of a = 1 mm from the end face of the grinding tool 2. The drill was set so that its axis of rotation 5 was at an angle θ = 46 ° 97 ′ to the axis of rotation 4 of the grinding tool 2, while the value of the angle θ was chosen such that it ensured when sharpening the drill 1 a given normal rake angle γ = 30 ° at the periphery of the drill 1.

Then, the grinding tool 2 was informed about the rotation around its axis of rotation 4 in the direction of the arrow C and sharpening the drill 1 by means of simultaneous and coordinated actions: turning the drill 1 around its cutting edge 3 in the direction of the arrow D; moving the drill 1 along its cutting edge 3 in the direction of the arrow E over the entire length of the cutting edge 3 starting from its periphery; the movement of the drill 1 along the axis of rotation 4 of the grinding tool 2 in the direction of the arrow F. At the end of sharpening, the cutting edge 3 of the drill 1 was positioned from the end of the grinding tool 2 at a distance b = 0.5 mm.

As the grinding tool 1, a straight profile grinding wheel was used.

Thanks to the specified kinematics of sharpening the drill along the front surface, it becomes possible to control the distribution of normal rake angles along the cutting edge during sharpening. The value of the normal rake angle in each section of the cutting edge 3 was determined by the angle of rotation of the drill 1 around its cutting edge 3 in the direction of arrow D. This allows you to both increase and decrease the normal rake angle in this section of the cutting edge 3, regardless of the value of the normal rake angle by neighboring areas, thereby affecting the distribution of wear of the sections of the cutting edge 3 of the drill 1 and its resistance. In addition, when sharpening the drill 1, the new front surface forms a chip breaking groove with a variable width, taking the values "a" and "b" at the edges. The optimal groove width at each point of the cutting edge 3, allowing the most efficient crushing of the chips generated during drilling, is determined by the movement of the drill 1 along the axis of rotation 4 of the grinding tool 2 in the direction of the arrow F.

Thus, the claimed invention allows to obtain the optimal value of the normal rake angle at each section of the cutting edge, which leads to equalization of wear of the sections of the cutting edge of the drill.

Table 1 is presented below, which confirms the materiality of the intervals stated in the claims.

The analysis of the claimed technical solution for compliance with the conditions of patentability showed that the characteristics indicated in the independent claim are interrelated with each other with the formation of a stable set of necessary attributes unknown at the priority date from the prior art sufficient to obtain the required synergistic (over-total) technical result.

The properties regulated in the claimed compound by individual features are well known in the art and require no further explanation.

Thus, the above information indicates the fulfillment of the following set of conditions when using the claimed technical solution:

- the object embodying the claimed technical solution, in its implementation is intended for use in the field of machine tool industry, in particular, for the manufacture of metal cutting tools and can be used for sharpening drills;

- for the claimed object in the form described in the independent claim, the possibility of its implementation using the means and methods known from the prior art on the priority date on the priority date has been confirmed;

- the object embodying the claimed technical solution, when implemented, is able to ensure the achievement of the technical result perceived by the applicant.

Therefore, the claimed subject matter meets the requirements of patentability “novelty”, “inventive step” and “industrial applicability” under applicable law.

Claims (1)

A method of sharpening drills on the front surface, including positioning the drill so that its cutting edge is perpendicular to the axis of rotation of the grinding tool, followed by sharpening the drill by moving it relative to the grinding tool along the cutting edge of the drill, starting from its periphery, characterized in that when positioning the drill, its cutting edge is located from the end of the grinding tool at a distance "a" of (0.01-0.45) d, where d is the diameter of the drill, and the drill was installed ayut so that its rotation axis is at an angle θ to the axis of rotation of the grinding tool, the angle θ is determined from the following relation:
$$\theta =\arccos \left(\sin \phi \cdot \cos \left(\gamma +\arccos \sqrt{\frac{d^2-\mathrm{four}{r}_c^2}{d^2-\mathrm{four}{r}_c^2\cdot {\sin }^2\phi }}\right)\right),$$

where φ is the drill angle in plan;
γ is the specified normal rake angle at the periphery of the drill;
r _with - radius of the core of the drill;
while sharpening is carried out by coordinated rotation of the drill around its cutting edge, moving the drill along its cutting edge over its entire length and moving the drill along the axis of rotation of the grinding tool, and at the end of sharpening, the cutting edge of the drill is placed from the end of the grinding tool at a distance "b", component (0.01-0.45) d, and as a grinding tool use a grinding wheel with a direct profile.

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