JPH0337858Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a comparatively small-diameter indexable end mill, which reduces cutting resistance by having a large regular rake angle in the axial direction.
Moreover, by improving the cutting edge configuration, it is possible to perform right-angled shoulder cutting with high straightness. Conventionally, it has been known that with this type of indexable end mill, if the rake angle in the axial direction is a large regular angle, the cutting resistance will be reduced, chip evacuation will be improved, and the tool life will be longer. There is. However, when performing right-angle cutting, as the outer diameter of the cutting edge becomes smaller, it becomes impossible to set the rake angle in the axial direction to a large regular angle. this is,
If a flat indexable tip that forms a straight cutting edge is applied to a tool with a small outer diameter of the cutting edge,
This is because, unlike the cutting edge which is twisted, the geometrical relationship gives the wall surface of the workpiece W a convex shape as shown in FIG. 10. As a result, indexable end mills with a large regular axial rake angle cannot be applied to right-angle milling that requires a certain degree of precision. On the other hand, in order to eliminate the above-mentioned disadvantages of the convex shape, it is possible to apply an end mill with a long twisted blade tip disclosed in Japanese Patent Publication No. 53-22717, for example. However, the long twisted blade tip must be prepared in many types depending on the size of the outer diameter of the cutting edge, which has the disadvantage of complicating tool management.
Therefore, end mills that clamp long twisted tips have hardly been put into practical use. For this reason, in small-diameter end mills that use indexable tips whose basic shape is a polygonal plate, which is the most versatile, the cutting edge is designed to minimize the convex shoulder wall seen in right-angled shoulder milling. There is a demand for the development of a throw-away end mill with an improved shape. The present invention was developed in view of the above-mentioned points, and a polygonal plate-shaped throw-away tip is installed in the mounting groove provided on the outer circumference of the cylindrical tool body. By improving the cutting edge configuration of the indexable end mill, which is built so that its outer surface forms a flank surface, it is possible to create a square shoulder with high straightness even when the rake angle in the axial direction is a large square angle. It is designed to allow sharpening. Hereinafter, one embodiment of the indexable end mill of the present invention will be described with reference to the drawings. In FIGS. 1 to 3, reference numeral 1 denotes a cylindrical tool body, and a mounting groove 3 in which a chip pocket 2 is connected is formed on the outer circumferential portion of the tool body. For example, a throwaway tip 5 in the shape of a substantially parallelogram plate can be received. This throw-away tip 5 is fixed by a presser foot 7 equipped with a tightening bolt 6, and its polygonal surface is a rake surface 8, and its outer surface is a flank surface 9.
Configure each. In this case, the axial rake angle α is 13° to 20°, and the radial rake angle β is −7°.
It is set within the range of ~3°. This is particularly because it is intended to reduce cutting resistance and because it is intended for relatively small diameter end mills, such as those with a cutting edge outer diameter of about 20 to 63 mm. Furthermore, the indexable end mill of the present invention cannot be applied to right-angle shoulder milling because the rake angle α in the axial direction described above is a large regular angle, and a convex wall is normally formed. Therefore, in the present invention, as a countermeasure, the convex curved outer cutting edge 1
0 is adopted. Therefore, this outer circumferential cutting edge ridge 10 is obtained by having the flank surface 9 on the outer circumferential side having a large radius of curvature R, as shown in FIGS. 4a and 4b. In this case, this radius of curvature R is 220
Set within the range of ~300mm. That is, as shown in FIG. 10, the error X from the wall surface and the wall surface approximate arc radius R ₀ of the workpiece W are given by the following formula, and the radius of curvature of the throwaway tip 5 is 220 to 300 mm. was selected. X=r ₀ −r ₁ ...(1) R ₀ =4x ² +h ₂ /8x ...(2) Here, in the above formula, r ₀ and r ₁ are the radial distance from the tool center, and h is the radial distance from the tool center. , represents the maximum depth of cut, and equation (2) is derived from the following equation. R ₀ ² = (R ₀ -x) ² + (h ² /2) ...(3) Also, the radius of curvature R of the throwaway tip 5 described above is determined by the relationship between the axial rake angle α and the radial rake angle β. From, the aforementioned approximate arc radius R ₀
Differently, the following equation is given as an approximate circular arc radius by the linear cutting edge L corresponding to the projected maximum depth of cut h and the error x from the wall surface. R = 4x ² + L ² / 8x ...(4) Therefore, in the actual calculation of R ₀ and R, the results shown in the following table are obtained, and as a general preferred range, R =
220-300mm is selected.

[Table] Figures 5 and 6 show modified examples, respectively, and the throwaway tip 5 has
A central mounting hole 11 is drilled, and the throw-away tip 5 is fixed in the chip seat 4 using a screw 12 using the central mounting hole 11. In FIG. 6, in order to further increase the clamping force of the throwaway tip 5, it is also fixed by the aforementioned presser foot 7 and tightening bolt 6. Furthermore, FIGS. 7 and 8 show another modification, in which the approximately triangular plate-shaped throw-away tip 5 shown in FIGS. 9a and 9b is applied. In this case, a locator 13 is installed in the installation groove 3 of the tool body 1, and this locator 1
Throwaway tip 5 in tip seat 4 of 3
is the wedge piece 14 and the screw 15 from the front side in the direction of rotation.
It is fixed by 7 and 8 adopt the so-called front wedge method in which the throw-away tip 5 is fixed from the front surface in the rotation direction with a wedge piece 14, but the method is not limited to this. A so-called rear wedge method of fixing with a piece 14 may also be adopted. Further, as shown in FIG. 9, the throwaway tip 5 may have an oblique chamfer 16 formed at its apex portion. The indexable end mill configured in this manner has the following technical effects. First, the perpendicularity of the wall surface of the workpiece in right-angle shoulder milling increases. This is because an axial rake angle α constituting a large regular angle is provided, so a normal straight cutting edge edge causes a convex wall error x, but in the present invention, the outer cutting edge edge 10 of the throw-away tip 5 Since the wall has a radius of curvature R, the perpendicularity of the wall surface is increased. That is, FIG. 11 shows the wall surface error x obtained by actual cutting for the product of the present invention and the comparative product, and it is clear that the product of the present invention is superior in perpendicularity. In this case, the workpiece material is SCM440 (H _B
234), and the cutting conditions are cutting speed V = 114 m/
min, feed f = 0.05 mm/tooth, and cutting width W = 2 mm. In addition, the tool specifications shown in Figures 1 to 3 are applied to the product of this invention, with a single flute with an outer diameter of the cutting edge = φ50 mm, an axial rake angle α = 14 °, and a radius of Directional rake angle = β−
5°, the shape of the throwaway tip 5 is as follows: long side opposite side dimension = 16 mm, short side opposite side dimension = 12 mm, thickness = 3 mm, opposite angle = 85°, relief angle = 20°, radius of curvature R = 260 mm. This is what I did. As a result, the product of the present invention had a wall surface error x that was much smaller than that of comparative product B of the throw-away type. Comparative product B incorporates a triangular chip, and the main differences are that the effective cutting edge length of the straight cutting edge is 12.5 mm, α = 17°, and β = 1°. Comparative product C has a diameter of 50 mm with an axial twist angle of 20°.
This is a brazing type end mill. In addition, when the depth of cut was increased, the wall surface error x was smaller for product A of the present invention than for comparative product C. However, this is due to installation error on the machine tool,
It was determined that this was due to the spindle runout, etc., and that there was no significant difference. Second, the cutting conditions are also good. This was confirmed from the cutting test mentioned above.
It was superior to comparative product B, which had a straight cutting edge, in terms of chatter vibration.

[Brief explanation of drawings]

FIG. 1 is a partial front view showing one embodiment of the indexable end mill of the present invention, and FIG.
Its bottom view, Figure 3 is a partial side view, Figure 4 is
One embodiment of the throw-away tip incorporated in the indexable end mill of the present invention is shown, in which a is a front view, b is a side view thereof, FIG. 5 is a partial side view showing a modified example, and FIG. 6 is another example. FIGS. 7 and 8 are views showing still another modification, where FIG. 7 is a front view and FIG. 8 is a partially cutaway side view of the main part. , FIG. 9 is a diagram showing the throw-away tip, where a is a front view, b is a side view,
FIG. 10 is an explanatory diagram showing the situation of the wall surface error of the workpiece, and FIG. 11 is an explanatory diagram showing the results of measuring the wall surface error x in actual cutting. 1... Tool body, 3... Mounting groove, 5... Throwaway tip, 8... Rake face, 9... Flank surface, 10... Outer cutting edge ridge.

Claims (1)

[Claims for Utility Model Registration] A polygonal plate-shaped throw-away tip 5 is placed in a mounting groove 3 provided on the outer periphery of a cylindrical tool body 1, with a rake surface 8 on its polygonal surface, and a rake surface 8 on its polygonal surface. In a throw-away end mill that is assembled so as to form a flank surface 9 on its side surface, the throw-away tip 5 has an axial rake angle α of 13° to 20° when it is assembled into the mounting groove 3. °, the rake angle β in the radial direction is within the range of -7° to 3°, and the outer peripheral cutting edge ridge 10 is formed by the rake face 8 and the outer peripheral side flank face 9 consisting of a convex curved surface. , an indexable end mill characterized in that the radius of curvature R of the outer cutting edge 10 is within the range of 220 to 300 mm.