JPS5939245B2 - Drill for machining high manganese non-magnetic steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drill suitable for drilling holes in high manganese non-magnetic steel.

High manganese non-magnetic steel was developed as a new alloy steel with mechanical strength that is several orders of magnitude better than the conventional non-magnetic steel austenitic stainless steel. , its rigidity is extremely poor and it falls under the so-called difficult-to-cut material in terms of machining characteristics, and the degree of difficulty in machining is 2 to 3 in terms of the number of holes drilled with a conventional drill developed for difficult-to-cut materials. It is about 1 piece.

Therefore, there has been a demand for a drill with excellent performance when using this high manganese non-magnetic steel with excellent mechanical strength for various purposes.

In view of the above-mentioned current situation, the inventors conducted various experiments as described below.

In general, a larger point angle than usual is recommended for difficult-to-cut materials, so first, let's look at the details of the drill specifications for machining high manganese non-magnetic steel using a drill with a 140 degree point angle. Table 1 shows the cutting conditions, and Table 2 shows the cutting conditions.

As a result, under the various cutting conditions mentioned above, only one or two holes were made in each case, and when the drills were observed after their lifespan, the chisel part was completely worn out, and it was assumed that this was the root cause that determined the lifespan. .

The reason for this is that the chisel angle β of the drill is known as
is a negative angle as shown in Fig. 1, and the cutting speed of the chisel part C is close to zero, so the chisel part C is exposed to being pushed in with almost no cutting, and the high manganese non-magnetic material It is thought that this combination of the material property of steel, which is that it is extremely hard to work, causes damage to the chisel part, which increases the cutting resistance and shortens tool life.

Next, in order to change the length of the chisel part C, the drill was subjected to various types of thinning S as shown in Figure 2, and cutting was performed under the same conditions as shown in Table 2. There was significant wear on the cutting edge, and there was no change in the lifespan.

This is because the two-stage cutting edge shape of the primary cutting edge of the main cutting edge and the secondary cutting edge of the auxiliary cutting edge formed by normal thinning is completely ineffective on bulky manganese-based non-magnetic steel. It showed that.

Therefore, as shown in Fig. 3, the chisel part is almost eliminated to create a chisel point cp, that is, the cutting edges 1, 1 are arranged approximately in a straight line so as not to form a secondary cutting edge, and thinning is applied to the blade. vertically, the tip core thickness p is 2.5 mm, 1.5
Among the cutting conditions in Table 2 for three types: mm and 0.5 mm,
Cutting speed 4.08m/mi, feed 0.1mm/re
When machining was performed using the Vs cutting method with a length of 30 mm, the tip core thickness P was obtained without a secondary cutting edge, as shown in Figure 4.
It has been found that the smaller the number of holes to be machined N, that is, the tool life is extended.

Furthermore, in order to investigate the action and effect of axial rake α,
The tip core thickness P, which had the longest life among the above drills, was 0.5 m.
The influence of the axial rake was investigated by applying constant axial rake at three levels of -5 degrees, 0 degrees, and 5 degrees to a No. m drill, and changing only the axial rake without changing the cutting conditions.

Generally, the axial rake of a drill cutting edge with a normal cutting edge is uniquely caused by the shape of the drill groove, but it does not exist at a constant value and as it reaches from the outer peripheral margin part 2 to the chisel part C, This is because the influence of axial rake was not accurately understood because it tends to rise in the negative direction.

As a result, the tool life can be further extended by setting the axial rake α to a constant positive value as shown in Fig. 5, whereas it was as shown in Fig. 4 in the case of the above-mentioned drill with an indeterminate axial rake. I found out.

The present invention was made based on the above-mentioned findings, and is characterized by the fact that, in a drill having a tip angle of 130 degrees to 150 degrees, a pair of cutting blades sandwiching a chisel point are arranged almost in a straight line. However, a constant positive axial rake is applied to the entire cutting edge from the chisel point to the outer peripheral margin.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

In Fig. 6, φ is the tip angle, γ is the second tip angle, CP is the chisel point, P is the tip core thickness, and α is the axial rake.
40 degrees, second tip angle γ is 6 degrees, chisel point CP
The rake face 3 of the drill D, which has been thinned and raised so that the cutting blades 1, 1 are arranged almost in a straight line with
It is formed by cutting as shown by the broken line in the figure so that a constant positive axial rake is formed over the entire area of the cutting edges 1, 1 from P to the outer circumferential margin part 2.

The characteristic requirements of the present invention are that the cutting edges 1, 1 are arranged almost in a straight line so that no secondary cutting edge is formed, and that the cutting edge 1
, 1. As a result, as is clear from a comparison of FIG. 2 and FIG. In contrast, in the drill of the present invention, the corner portion is removed and is formed as a flat portion 5, which also has a favorable effect on tool life.

That is, high manganese nonmagnetic steel, which is severely work hardened in a sharp state, wears out quickly, but the flat part 5 is hard to wear due to its shape.

The cutting performance of the drill of the present invention having the above-mentioned configuration is as shown by the circle ◎ in FIG. It is possible to provide a drill that can machine high manganese non-magnetic steel.

It is clear that it is sufficient to apply a constant positive axial rake, but if the rake is made too large, the strength of the cutting edge will decrease significantly, so in practice, 3 degrees to 15 degrees is preferable.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the chisel angle, Figure 2 is an explanatory diagram of conventional thinning, Figure 3 is an explanatory diagram of the chisel point, Figure 4 is a diagram showing the influence of tip core thickness on life, Figure 5 is a diagram showing the influence on the life of the axial rake, Figure 6
The figure is a detailed explanatory diagram of the present invention. 1: Cutting edge, 2: Peripheral margin, 3: Rake face, 4: Cutting blade outer corner, 5: Flat part, α: Axial rake,
L: Secondary cutting edge, B: Chisel angle, S: Thinning part, φ:
Tip angle, P: Tip core thickness, γ: Tip second angle, CP: Chisel point.

Claims (1)

[Claims] In a drill having a tip angle of 1130 degrees to 150 degrees, a pair of cutting blades sandwiching a chisel point are arranged substantially in a straight line, and the entire cutting blade area from the chisel point to the outer peripheral margin is A drill for machining high manganese non-magnetic steel characterized by a constant positive axial rake. 2. The drill according to claim 1, wherein the axial rake is 3 degrees to 15 degrees.