RU2528593C2 - Twist drill with curvilinear lip - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to machine building and can be used at drilling holes, for example, in cast iron. Drill comprises cutting edge made to ensure invariable wear of its points at hole processing. Cutting edge projection to plane to perpendicular to drill rotational axis is defined depending on polar angle of current point of cutting edge projection to the plane perpendicular to drill rotational axis. Said polar angle is counted from projection initial point in direction opposite that of drill rotation, radius of circle wherein belongs the current point of cutting edge protection to the plane of drill rotational axis, radius of circle wherein belongs the initial point of cutting edge protection to the plane of drill rotational axis, and drill core radius.

EFFECT: higher hardness of helical drill.

1 tbl, 3 dwg

Description

The invention relates to the field of tool industry, in particular to twist drills for drilling holes in hard-to-work materials and alloys (for example, cast iron, heat-resistant steel).

The prior art spiral drill with a constant rake angle, the cutting edges of which are curved (USSR Author's Certificate No. 49722, B23B 51/02, 1936).

A disadvantage of the known technical solution is the uneven wear of the points of the cutting edges of the twist drill due to a change in cutting speed along the cutting edge and leading to a decrease in the resistance of the twist drill.

The closest technical solution to the proposed invention is a drill whose cutting edges in a plane perpendicular to the axis of rotation are made in the form of a spiral curve, the ratio of the length of any portion of which to the size of the corresponding area described by the drill during rotation is a constant value (USSR Author's Certificate No. 715238 B23B 51/02, 1980).

A disadvantage of the known technical solution is also the uneven wear of the points of the cutting edges of the twist drill due to a change in cutting speed along the cutting edge and leading to a decrease in the resistance of the twist drill.

The technical task of the invention is to increase the resistance of the twist drill by aligning the projection of the cutting speed vector of the points of the cutting edge on normal to the projection of the cutting edge on a plane perpendicular to the axis of rotation of the drill.

The problem is solved by the fact that in a spiral drill with curved cutting edges, according to the invention, the cutting edge in the projection onto a plane perpendicular to the axis of rotation of the drill is determined by the equation:

, $$\mu =\arcsin \left(\frac{R}{r}\right)+\frac{\sqrt{r^2-R^2}}{R}-\frac{\mathrm{<figure-callout\; id="2"\; label="\pi "\; filenames="00000006.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{2}$$

,

where µ (rad) is the polar angle of the current point of projection of the cutting edge on a plane perpendicular to the axis of rotation of the drill, counted from the starting point of the projection in the direction opposite to the rotation of the drill during processing;

r is the radius of the circle to which the current point of the projection of the cutting edge on the plane perpendicular to the axis of rotation of the drill;

R = (1.05-2) R _C is the radius of the circle to which the starting point of the projection of the cutting edge on a plane perpendicular to the axis of rotation of the drill belongs;

R _C is the radius of the core of the twist drill.

The invention is illustrated by drawings, where:

- figure 1 is a view of the claimed twist drill in isometry;

- figure 2 is a projection of the drill on a plane perpendicular to its axis of rotation;

- figure 3 is a projection of the drill on a plane parallel to its axis of rotation, where respectively are shown:

1 - cutting edge;

2 - projection of the cutting edge on a plane perpendicular to the axis of rotation of the drill;

3 - a plane perpendicular to the axis of rotation of the drill;

4 - axis of rotation of the drill;

5 - the current point of projection of the cutting edge on a plane perpendicular to the axis of rotation of the drill;

6 - the initial point of projection of the cutting edge on a plane perpendicular to the axis of rotation of the drill;

7 - cutting speed vector at the current point of the cutting edge;

8 - the current point of the cutting edge;

9 is a projection of the cutting speed vector at the current point of the cutting edge on the normal to the projection of the cutting edge on a plane perpendicular to the axis of rotation of the drill;

10 - normal to the projection of the cutting edge on a plane perpendicular to the axis of rotation of the drill;

11 is a projection of the cutting speed vector at the current point of the cutting edge on the tangent line to the projection of the cutting edge on a plane perpendicular to the axis of rotation of the drill;

12 - a tangent line to the projection of the cutting edge on a plane perpendicular to the axis of rotation of the drill;

The inventive spiral drill contains a cutting edge 1, the projection 2 of which on the plane 3, perpendicular to the axis 4 of rotation of the drill, is determined by the equation:

, $$\mu =\arcsin \left(\frac{R}{r}\right)+\frac{\sqrt{r^2-R^2}}{R}-\frac{\mathrm{<figure-callout\; id="2"\; label="\pi "\; filenames="00000006.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{2}$$

,

where µ (rad) is the polar angle of the current point 5 of the projection 2 of the cutting edge 1 on the plane 3, perpendicular to the axis 4 of rotation of the drill, counted from the starting point 6 of the projection 2 in the direction opposite to the rotation of the drill during processing;

r is the radius of the circle to which the current point 5 of the projection 2 of the cutting edge 1 on the plane 3 belongs, perpendicular to the axis of rotation 4 of the drill;

R = (1.05-2) R _C is the radius of the circle to which the starting point 6 of the projection 2 of the cutting edge 1 on plane 3 belongs, perpendicular to the axis of rotation 4 of the drill;

R _C is the radius of the core of the twist drill.

The cutting edge 1 belongs to the surface of rotation of the straight line, inclined in the axis of rotation of the drill 4 by an angle equal to the main angle of the drill in terms of φ, relative to the axis coinciding with the axis of rotation of the drill 4. The front and rear surfaces of the drill are made by sharpening the drill with the formation of the front angle γ and back angle α. The helical groove of the drill is inclined to the axis of rotation of the drill 4 at an angle ω.

At the production site of GOU FSBEI HPE MSTU STANKIN, the proposed design was tested, namely a twist drill with a diameter of 30 mm, a core radius R _C = 3 mm, a cutting length of 70 mm, designed to process holes with a depth of 50 mm in billets made of gray cast iron MF30.

The cutting edge 1 of the drill was made so that its projection 2 on the plane 3, perpendicular to the axis 4 of rotation of the drill, was determined by the equation:

, $$\mu =\arcsin \left(\frac{6}{r}\right)+\frac{\sqrt{r^2-36}}{6}-\frac{\mathrm{<figure-callout\; id="2"\; label="\pi "\; filenames="00000006.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{2}$$

,

where µ (rad) is the polar angle of the current point C of the projection 2 of the cutting edge 1 on the plane 3, perpendicular to the axis 4 of rotation of the drill, counted from the starting point 6 of the projection 2 in the direction opposite to the rotation of the drill during processing;

r is the radius of the circle to which the current point 5 of the projection 2 of the cutting edge 1 on the plane 3 belongs, perpendicular to the axis of rotation 4 of the drill.

The cutting edge 1 belonged to the surface of rotation of the straight line, inclined in the axis of rotation of the drill 4 by an angle equal to the main angle of the drill in terms of φ = 59 °, relative to the axis coinciding with the axis of rotation of the drill 4. The front and rear surfaces of the drill were made by sharpening the drill with the formation of the front angle γ = 10 ° and rear angle α = 12 °. The helical groove of the drill was inclined to the axis of rotation of the drill 4 at an angle ω = 30 °.

The vector of cutting speed 7 at the current point 8 of cutting edge 1 is postponed from the projection of point 8 onto plane 3 — points 5 and decomposed into two components — the projection 9 of the vector of cutting speed 7 to normal 10 to projection 2 and the projection 11 of the vector of cutting speed 7 to the tangent line 10 to projection 2.

During drilling, the wear of the current point 8 of the cutting edge 1 of the drill was determined mainly by the projection 9 of the cutting speed vector 6 to normal 9 to projection 2, because the second component of the cutting speed vector 7 is the projection 11 of the cutting speed vector 7 on the tangent line 12 to the projection 2 during the drilling process corresponded to the movement of the cutting edge 1 at point 8 along itself, which did not lead to the removal of the allowance and to the wear of the cutting edge 1 at the point 8.

Due to the indicated geometry of the cutting edge 1, the projection 9 of the cutting speed vector 7 to normal 10 to projection 2 at its current point 5 was constant and amounted to 0.4 v, where v (m / min) is the drilling speed specified by the modes, therefore, the wear of the points cutting edge 1 was constant. The cutting edge 1 did not contain a section or sections with increased wear compared to the rest of the sections. The presence of sections of the cutting edge 1 with increased wear and determines the low resistance of the known twist drill, which was 50 minutes The durability of the declared twist drill was determined by the wear of all sections of the cutting edge 1 and amounted to 75 minutes, which exceeds 1.5 times the durability of the twist drill known from the prior art.

Thus, the claimed combination of essential features set forth in the claims allows to increase the resistance of a twist drill by 1.5 times compared with the known twist drill.

The significance of the intervals claimed in the claims is confirmed in the Table.

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 invention 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 tool industry, relates to the manufacture of twist drills intended for machining holes in hard-to-work materials and alloys;

- 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 spiral drill with curved cutting edges intended for machining holes in cast iron blanks, characterized in that the cutting edge is made from the condition of ensuring constant wear of its points when machining the said holes, while its projection onto a plane perpendicular to the axis of rotation of the drill is determined by the equation:

,
where µ (rad) is the polar angle of the current point of projection of the cutting edge on a plane perpendicular to the axis of rotation of the drill, counted from the starting point of the projection in the direction opposite to the rotation of the drill during processing;
r is the radius of the circle to which the current point of the projection of the cutting edge on the plane perpendicular to the axis of rotation of the drill;
R = (1.05-2) R _C is the radius of the circle to which the starting point of the projection of the cutting edge on a plane perpendicular to the axis of rotation of the drill belongs;
R _C is the radius of the core of the twist drill.

Images