JPH061290Y2 - Slow away end mill - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to an improvement of a throwaway end mill having a relatively small diameter used in the work of a milling machine.

[Prior art]

Up to now, as a throwaway end mill having an outer diameter of about 20 mm and a relatively small diameter, the one shown in FIG. 5 has been used. FIG. 5 (a) is a side view, and FIG. 5 (b) shows the attachment part of the throw-away tip (hereinafter simply referred to as tip) viewed from the Y direction in FIG. 5 (a).
In the figure, A is a triangular tip and B is a cylindrical tool body, and the tip A is detachably fixed to a tip seat provided near the tip of the body B with a clamp piece.

In this type of end mill, since the tool diameter is small and various restrictions are imposed on the structure for mounting the tip, the radial rake angle (Rr) and axial rake angle (Ar) required for cutting performance cannot be selected in a wide range. Rr-3 to +3 degrees, A
It is used with a value of r0 to 5 degrees, but is not sufficiently satisfied from the viewpoint of cutting performance, and improvement is expected.

[Problems to be solved by the invention]

That is, in this kind of throw away end mill having a small outer diameter, when the tip seat is provided at the tip mounting portion, the wall thickness of the tool body under the tip seat tends to be thin, and the strength tends to decrease.

On the other hand, in order to improve the cutting performance, it is necessary to increase Rr and Ar in the cutting edge in the positive direction. In this case, in order to satisfy this requirement by using the conventional tip as it is, it is necessary to further deepen the surface of the tip seat to form a tip seat that satisfies the required rake angle. In the small-diameter end mill, as a result, the thickness of the lower part of the tip seat becomes remarkably small, which causes problems such as vibration during use and deterioration of cutting performance due to deterioration of strength and rigidity, and eventually causes damage. In addition, it is not possible to attach two relatively large inserts (for example, TPGN32 type) in order to secure the peripheral cutting edge length to the conventional small diameter end mill with an outer diameter of around 20 mm. Performance is inferior to that of a 2-flute type end mill. Therefore, the present invention provides a rake angle required for a cutting edge of a small-diameter throw-away end mill, and prevents the strength of the tool body from being lowered due to the rake angle.
It is an object of the present invention to provide a solution capable of mounting two chips each having a relatively long cutting edge even in a small-diameter end mill having an outer diameter of about 20 mm used for a single-blade.

[Means for solving problems]

The gist of the present invention for achieving the above object lies in the scope of the utility model registration claim. Fig. 3 (a) ~
(C) is a schematic bottom view showing the positional relationship between the tool body and the tip, and FIG. (A) shows the case where the radial rake angle and the axial rake angle of the outer peripheral cutting edge of the tip are set to zero.
P'is a circle of the rotary axis of the cutting edge due to the tool diameter D, and its center is O. 2 is a throw-away tip, the rake face is 3, the bottom face is 4, the cutting edge is P, and the flank face is P-R.
Here, R indicates the edge of the bottom surface of the chip. The intersection point between the extension line of the bottom surface 4 and the circle P'is Q, and the angle formed by the tangent line PT of the circle P'at the cutting edge P and PQ is θ1. A gap for preventing friction between the work surface and the tool during cutting. If the angle is θ2, the clearance angle θ of the insert is θ = θ1 + θ2, and the tool body is also PR
It is designed not to cross the line. Therefore, in the case of the same chip thickness, the smaller the outer diameter, that is, the smaller the circle P ', the larger θ1 becomes, and therefore the clearance angle θ needs to be increased, and the tool body holding the chip is inevitably small accordingly. As a result, the thickness of the lower part of the tip seat is reduced, and the strength and rigidity are reduced.

Next, FIGS. 3 (b) and 3 (c) show the case where the radial rake angle δ is changed from zero to positive or negative. The rake face position of the tip 2 when the rake angle δ in the radial direction is positive is represented by 3 ′ in FIG. 3 (b). In this case, the thickness of the lower tip seat of the tool body holding the tip is reduced. The strength is significantly reduced. On the contrary, as shown in FIG. 3 (c), when the radial rake angle δ is made negative, the rake face of the tip 2 occupies the position of 3 ″, and thus the bottom face of the tip seat also has a negative angle. The chip holding strength of the tool body is improved because it is formed in the.

A similar phenomenon occurs at the axial rake angle. That is,
If the rake angle is positive, the tool strength in the insert holding part will decrease, but its impact is less than that in the radial rake angle, and as a result of experiments, when the outside diameter of the tool is around 20 mm, the insert size is roughly It has been found that when the radial rake angle is negative with the direction of 12 to 16 mm, the radial direction of 8 to 10 mm, and the thickness of 2.5 to 3 mm, the axial rake angle of 15 ° or less causes no practical problem. As for the radial rake angle, it is well known that the cutting resistance can be proportionally reduced as the rake angle is increased to a regular angle, and the cutting performance is improved.

By the way, in order to secure the strength and rigidity of the chip holding portion, as shown in FIG. 3 (c), the bottom surface of the chip seat is formed so as to hold the chip 2 at the position where the radial rake angle is negative. It is considered necessary to do so. That is, if the chip seat bottom surface is formed so that the chip rake surface is located at the position of 3 ", the strength reduction due to the positive rake angle in the axial direction can be alleviated, and the effect is further enhanced.

As mentioned above, in order to improve the strength of the chip holding portion,
It is necessary to form the bottom surface of the chip seat so that the surface of the chip 2, which is the upper surface, forms a negative angle with respect to the radial direction, but it is necessary to prevent the cutting performance from deteriorating and to improve the performance. The present invention has been presented. That is, by providing a groove such as a chip breaker at a position close to the cutting edge along the outer peripheral cutting edge in parallel with the cutting edge, by appropriately selecting the slope angle of the cutting edge side of the groove, We paid attention to the fact that the radial rake angle can be maintained at a positive value. In other words, the rake face, which is the upper face of the insert, forms the insert seat bottom surface so that the negative angle is formed in the radial direction to improve the insert holding strength of the tool body, and to improve the insert breaker-like groove provided along the outer peripheral cutting edge. Depending on the slope angle,
Set the substantial radial rake angle to a positive appropriate value,
By improving the cutting performance and using the parallelogram flat plate-shaped boge tip, it was possible to obtain a two-flute type having a relatively long cutting edge even in a throwaway end mill having a small diameter.

In addition, the throwaway tip in the shape of a parallelogram plate has a longer outer peripheral cutting edge, and when the angle r in FIG. The effect on the wall thickness is small and the long side is the outer peripheral cutting edge.

[Embodiment] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an example of a two-flute end mill according to the present invention,
1 (a) is a side view, FIG. 1 (b) is its X arrow view, and in the figure, reference numeral 1 is an end mill body, 2 is a throw-away tip,
3 is the rake face, 6 is a chip mounting screw, 5 is a chip breaker-like groove along the outer peripheral cutting edge, O is the center of rotation of the end mill, and P is the cutting edge of the chip. FIG. 2 shows the throw-away tip 2 attached to the end mill. FIG. 2 (a) is a plan view and FIG. 2 (b) is a side view thereof, in which 1 is the longitudinal dimension of the tip 2, w is the width dimension, t is thickness, α is groove 5
Shows the slope angle of.

In FIG. 1 (b), the radial rake angle δ is shown by the angle formed by the rake face 3 and OP, and the following relationship exists between the slope angle α of the groove 5 and the substantial radial rake angle β. is there.

β = α−δ In order to maintain the strength by increasing the thickness of the lower part of the chip seat, even if the bottom surface of the chip seat is formed so that δ is a negative angle, the slope angle α of the breaker-shaped groove 5 should be | α |> By properly selecting in the range of | δ |, it is possible to improve the cutting performance by setting the substantial radial rake angle β to an appropriate positive value.

Next, the reason for limiting the numerical value of the rake angle will be described.

A cutting test was conducted using an end mill having an outer diameter of 20 mm as shown in FIG. The results of cutting are evaluated in terms of vibration, cutting stability, breakage of the cutting edge, surface condition, sharpness, etc. from good to bad ◎ (Excellent), ○ (Good), △ (poor), × (bad)
The symbol is shown in the table below. The cutting test conditions for the outer diameter of 20 mm are shown in Table 1, and the evaluation of the results is shown in Table 2.

Therefore, the appropriate value for the radial rake angle δ is -5 ° to -15 °.
It is thought that the rake angle in the axial direction is 5 ° to 10 °.
Further, the substantial radial rake angle β is preferably in the range of 0 ° to 10 °.

Since similar results were obtained under other cutting conditions, the shape of the end mill of the present invention was determined as described above.

In addition, the present invention employs a parallelogram tip, which has a large cutting edge length even if the tip width is small, and has an outer diameter of 20
Since the 2-flute type even for around mm, it has a good cutting balance and is superior in terms of stable cutting and efficiency compared to the conventional single-flute type. I was able to measure.

In order to explain this situation, an experimental example will be shown below. That is, a stable cutting area in stainless cutting was compared between the conventional product having an outer diameter of 20 mm and the product according to the present invention. The cutting conditions are shown in Table 3, the specifications of both are shown in Table 4, and the cutting performance is shown in FIG.

As shown in FIG. 4, the present invention has a tip nose angle γ
Is 85 degrees, which is larger than that of the conventional triangular tip (γ = 60 °), and therefore has the strength of the tip of the cutting edge, and combined with good sharpness, the stable region is remarkably widened as shown in FIG. Also, since the number of blades is two, the table feed amount can be doubled compared to the conventional one-flute product, and it is clear that it is a very high performance throw away end mill.

Incidentally, the breaker-shaped groove provided along the outer peripheral cutting edge for making the substantial radial rake angle δ a positive angle is different from the chip breaker groove for so-called chip treatment used in the turning work, and is described above. By appropriately selecting the slope angle on the cutting edge side of the groove, the substantial radial rake angle is maintained at a positive value, and thus the original groove shape as shown in FIG. 2 may be used. However, it is within the scope of the technical idea of the present invention that the entire rake face is positioned lower than the inclined face following the cutting edge.

[Effect of device]

As described above, in the present invention, in the throw-away end mill having an outer diameter of about 20 mm, the bottom surface of the tip seat is formed so that the rake face, which is the upper surface of the throw-away tip, has a radial rake angle of -5 to -15 degrees. By increasing the wall thickness of the lower part of the tip seat and increasing the strength of the tool body, it is possible to give a relatively large rake angle in the axial direction of 5 to 10 degrees relative to the outer diameter size, and it is an effective rake for cutting. Since a chip-breaker-like groove having a slope angle is provided along the outer peripheral cutting edge so that the substantial radial rake angle acting as an angle is 0 to 10 degrees, excellent machinability is achieved by these synergistic effects. It could be an end mill.

In addition, by adopting a parallelogram positive tip, the small diameter size can also be made into a two-flute type having a relatively long cutting edge, which is excellent in terms of stable cutting and efficiency. Combined with the corner,
It was possible to make a high-performance, small-diameter throw-away end mill.

[Brief description of drawings]

FIG. 1 shows one embodiment of a two-blade throw-away end mill according to the present invention. FIG. 1 (a) is a side view,
FIG. 2 (b) is its X arrow view, FIG. 2 is a throw-away tip used in the present invention, FIG. 2 (a) is a plan view, and FIG.
Is a side view thereof, and FIG. 3 (a) is a schematic bottom view of the throw-away tip mounted at a radial rake angle of zero,
FIG. 3 (b) is a schematic bottom view when the radial rake angle is changed positively, and FIG. 3 (c) is a view showing the time when it is changed negatively, and FIG. 4 is the present invention and the conventional product. Fig. 5 shows a comparison of cutting performance with Fig. 5, Fig. 5 is an example of a throw-away end mill using a conventional triangular throw-away tip, Fig. 5 (a) is a side view, and Fig. 5 (b) is its Y arrow view. Indicates. 1: End mill body 2: Throw-away tip 3: Rake surface 5: Chip breaker groove 6: Set screw δ: Radial rake angle of throw-away end mill α: Slope angle due to breaker groove of throw-away tip β: Throw-away end mill Effective radial rake angle during use

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliography Sho 56-38717 (JP, U) Rikai 58-128814 (JP, U) Rikai 58-173405 (JP, U) JP 54- 2709 (JP, B2)

Claims (1)

[Scope of utility model registration request] 1. A two-blade throw-away end mill with a throwaway tip removably fixed in a pair of tip seats on the outer periphery of the tip of a tool body in the form of a parallelogram in the shape of a parallelogram. The rake face, which is the upper surface of the throw-away tip having a clearance angle, has a radial rake angle of -5 to -15 degrees and an axial rake angle of 5 to 10 degrees.
While forming the bottom surface of the tip seat so as to be at a certain degree, a chip breaker-like groove is provided along the outer peripheral cutting edge on the rake face of the throw-away tip, whereby a substantial radius when fixed to the tip seat. Direction rake angle is 0-10
The throw-away tip has an outer peripheral cutting edge on the long side, and the cutting edge is substantially parallel to the rotation axis of the tool body.