JPH04146018A - Stepped end mill and resin plate hole drilling - Google Patents

Abstract

PURPOSE:To make knife and tooth marks occurrence during resin material processing less noticeable and make it difficult to generate fusing of chips by providing small and large diametrical blade parts on the head edge of a tool, forming each of the blade parts in one blade and forming an addendum line mutually, discontinuous to each of the blade parts and on the opposite side of the center. CONSTITUTION:A small diametrical cutting blade part 2 and a large diametrical cutting blade 3 are respectively formed on the head edge of the shank 1 of a stepped end mill T being separated from each other in the axial direction so that they are positioned on opposite sides to each other in relation to the rotational center of each blade. The small diametrical cutting blade 2 is formed so that the setting angle of its bottom blade 21 is about 5 deg. and an addendum line 22 extends to the center of rotation, and the rake angle is about 20 deg., the clearance angle is about 20 deg. and the side face clearance angle is about 20 deg.. The large diametrical cutting blade part 3 is in a position separated from the small diametrical cutting blade part 2 in the axial direction, and the setting angle of a bottom blade 31 is about one degree and the addendum line 32 of the bottom blade 31 is formed up to the inside of an addendum diameter (r) of the small diametrical cutting blade part 2 and it is expressed as (r)>(d). Furthermore, the rake angle is about 20 deg., the clearance angle is about 20 deg. and the side face clearance is about 20 deg.. Additionally, the addendum lines of the small diametrical cutting blade part 2 and the large diametrical cutting blade part 3 are mutually discontinuous.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improved stepped end mill suitable for processing resin plates and a method for drilling stepped holes or through holes.

2. Description of the Related Art A conventional stepped end mill for resin processing has two or more blades arranged in a well-balanced manner around a rotating shaft, as shown in FIG. When performing machining as shown in FIG. 4 using this end mill, for example, the stepped end mill is inserted to a predetermined depth and moved laterally to perform the machining.

Resin machining is processed at a lower speed than wood machining because high-speed rotary cutting generates heat, which tends to cause chips to weld and cause defects on the cut surface.

Problems to be Solved by the Invention In end milling of resin materials, knife marks and tooth marks are usually dominated by the blade with the widest rotation radius of multiple blades, and one mark is formed per rotation. At low speed rotation, this mark on the cutting surface becomes more noticeable, so the feed speed cannot be increased very much. For this reason, when the material feeding speed was slowed down, the marks became less noticeable, the amount of cutting per blade decreased, and the thickness of the chips became thinner, making it easier for them to get caught between the cutting edge and the cutting surface, causing them to rub and weld. . Another problem is that the greater the number of blades, the more likely it is that the chip evacuation will be poor.

In addition, in drilling by thrusting, there is a problem in that continuous chips are cut every month, wrap around the tool, and some of them are swung around, creating concentric scratches on the surface of the workpiece with the center of the drilled hole. .

Therefore, in the machining shown in Fig. 4, when the machine first plunges to a predetermined depth, continuous chips are removed and concentric scratches are generated.
There is also a problem in that welding marks are formed on the cutting surface during cutting by lateral movement.

The present invention was developed in view of these problems with the conventional technology, and its purpose is to reduce the conspicuousness of knife marks and tooth marks when processing resin materials, and to create a stepped end mill that is less likely to cause chips to adhere. The present invention also aims to provide a pre-drilling method.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention is provided with a small-diameter cutting edge at the tip of the tool, and a large-diameter cutting edge separated in the axial direction.
Each blade part is a stepped end mill consisting of a single blade, and its cutting edge line is discontinuous with each blade part and formed on the opposite side of the center, and the bottom blade of the small diameter cutting part is rotating. 6
It is preferable that the bottom edge of the large-diameter cutting edge be formed to the inside of the cutting edge diameter of the small-diameter cutting edge.

In addition, as a method for drilling stepped holes etc. in a resin plate with a stepped end mill, as a preliminary process prior to drilling, a small diameter long hole is drilled into the resin plate using a small diameter cutting edge with a diameter larger than the radius of the large diameter cutting edge. The hole is cut to a length that is less than or equal to the major axis (or the diameter if it is a circular hole), and a large-diameter cutting blade is further inserted or penetrated by a predetermined amount on the elongated hole, and then the cutter is cut along the elongated hole or further into the elongated hole. A stepped hole or a through hole is formed by cutting with a large diameter cutting edge beyond the length of the elongated hole.

During operation, when the small-diameter cutting blade portion with the small snow-bottomed edge is rotated and plunged in, it is easy to cut with less resistance, and when cutting with one rotation of the l-blade, the thickness of the chips is twice as thick as that of two-flute blades. Even when cutting a large-diameter cutting edge, the thickness of the chips produced by one rotating blade is twice that of two blades.

When a stepped hole or a through hole is drilled, divided chips are obtained by cutting an arc of at least a half circle, preferably cutting an arc of a quarter circle or less.

Example Embodiments will be described below based on FIGS. 1 to 3.

A small diameter cutting edge part 2 is attached to the tip of the shank l of the stepped end mill T.
The large-diameter cutting blade portions 3 are formed so as to be spaced apart in the axial direction and located on the opposite side to the rotation center of each I-blade.

The small diameter cutting edge part 2 has a bottom edge 21 with a recess angle of approximately 5° and a cutting edge line 22.
is formed up to 6 during rotation, with a rake angle of approximately 20° and a clearance angle of approximately 2.
0°, side relief angle approximately 20°.

The large-diameter cutting edge 3 is located axially away from the small-diameter cutting edge, and the bottom edge 31 has an undercut angle of about 10, and the edge line 32 of the bottom edge extends to the inside of the edge diameter r of the small-diameter cutting edge. It is red.

The rake angle is about 20°, the relief angle is about 20°, and the side relief angle is about 20°. The cutting edge lines of the small diameter cutting edge portion 2 and the large diameter cutting edge portion 3 are discontinuous with each other. Also, the side blade 2 of the small diameter cutting blade part 2
3 is long and the rear end position is the same as that of the side blade 33 of the large-diameter cutting blade portion 3 in this example, but it does not necessarily have to be the same.

The large and small cutting edges formed in this way form a small-width elongated hole W a and a large-sized oval hole W as shown in Fig. 4 with each stepped end mill T.
First method for machining stepped oval holes, etc. consisting of b: Stepped oval holes (Figures 5 to 7) Place the resin plate W on the horizontally fed table of the processing machine, and use the stepped end mill. The stepped end mill T is positioned at the initial position to be drilled directly below the T, that is, moved inward by the radius of the large diameter cutting edge 3 from the end of the oval hole, and the stepped end mill T is rotated. As a preliminary process, a stepped end mill T is used to drill a through hole with the small diameter cutting edge 2 in step a, and then the resin plate W is drilled to the full length of the narrow elongated hole Wa in the traverse step. As a finishing process, the stepped end mill T is used to drill the oval hole wb to a much greater depth in step C, and from that position, the hole wb is cut to the full length of the oval hole wb, i.e. at the beginning, by the horizontal feed step d in the opposite direction. Drill to the plunged position. Then, in the pulling step e, the stepped end mill is pulled up.

2nd method: Stepped oval hole (Fig. 8 to Fig. 1O) Position the table so that the stepped end mill T is located approximately diametrically inside the bone of the large-diameter cutting blade from the end of the stepped oval hole to be drilled. . As a preliminary machining, a stepped end mill T is inserted and the small diameter cutting blade portion 2 performs drilling in step f, and the table is moved laterally to the position where the end of the small-width oval hole is to be processed in step g. At this position, drilling is performed to a predetermined depth using the large-diameter cutting blade part 3 in a plunging process.

As a finishing process, the table is moved in the direction of the already drilled small-width elongated hole in the traversal step i, and a stepped oval hole is drilled by a predetermined oval hole length, and then the stepped end mill is pulled up in the lifting step j.

Third method - Through oval hole (Figures 11 to 13) The edge of the oval hole in the workpiece W on the table is positioned at the outer periphery of the small diameter cutting edge of the stepped end mill T, and as a preliminary machining Drill an oval hole to the full length with the small diameter cutting blade part 2. Next, the difference between the approximate radius of the large-diameter cutting blade 3 and the radius of the small-diameter cutting blade is returned in a traversal step m, and a hole is drilled with the large-diameter cutting blade 3 in a thrusting step n. As a finishing process, an oval hole having the same width as the large diameter of the large-diameter cutting blade portion 3 is drilled in the same direction in the lateral feed step 0, and the stepped end mill is pulled up in the pulling step p.

4th method - Through hole (Figures 14 to 16) Position the workpiece at the center directly below the stepped end mill T, drill the hole with the small diameter cutting edge 2 in the plunging step q in preliminary machining, and continue drilling as it is. An oval hole is drilled in a horizontal feed step r with a length slightly shorter than the difference between the radius of the hole to be drilled (that is, the diameter of the large-diameter cutting blade) and the radius of the small-diameter cutting blade.

Next, in the reverse traversal step S, it is returned to the opposite side by drilling an oval hole with a length slightly shorter than the difference between the radius of the hole and the radius of the small diameter cutting blade, and returning it to the center position. In the finishing process, the large-diameter cutting blade part 3 performs penetrating drilling in the thrusting step t, and the stepped end mill T is pulled up in the pulling-back step U.

Note that the first to fourth drilling methods are not limited to the single-blade stepped end mill of the present invention, and can also be applied to a certain extent using the conventional stepped end mill shown in FIG. 17. However, even better effects can be obtained by using the stepped end mill of the present invention.

Note that the stepped holes 2 through holes described here include not only circular holes but also irregularly shaped holes and holes in which a portion of the periphery of the hole opens into the edge of the resin plate.

Effects As described above, the present invention has the following effects.

Since the stepped end mill of claim 1 has the minimum number of teeth, it is possible to increase the thickness of the chips, and the flute volume can be maximized, resulting in a good flow of chips between the cutting edge and the cutting surface. Pinching is suppressed.

In the stepped end mill according to the second aspect of the present invention, the cutting edge line is formed to the center, so that the resistance at the time of thrusting can be reduced. Furthermore, since the cutting edge line of the bottom edge of the large-diameter cutting blade is formed to the inside of the cutting edge diameter of the small-diameter cutting blade, the resistance when the large-diameter cutting blade also penetrates can be reduced.

In the drilling method according to claim 3, conventional large-diameter cutting blades are suddenly plunged by a predetermined amount and moved laterally to drill a stepped oval hole, so that continuous chips are cut at the time of thrust and concentric scratches are generated. However, in the present invention, such a problem does not occur. That is, by forming a narrow long hole in the small-diameter cutting edge through preliminary machining, the chips are divided without generating harmful continuous chips even in the initial stage of machining when the large-diameter cutting edge is inserted.

In addition, since the cutting blade is a single piece, the chips are thick and do not get caught, and welding does not occur, resulting in a good finished surface.

Pre-machining is performed over almost the entire length of the hole in 1/4 of the cases.
Since the cutting is performed in an arc smaller than a circle, the chips are sufficiently divided and welding during finishing is further reduced.

Note that the continuous chips in the initial drilling process with the small diameter cutting edge have a small cutting volume, and even if wrapping occurs, they only slightly wrap around the small diameter cutting edge and are cut off when drilling with the large diameter cutting edge. This is not a problem.

[Brief explanation of drawings]

Fig. 1 is a side view of the stepped end mill of the present invention, Fig. 2 is a front view thereof, Fig. 3 is a side view of the small diameter cutting edge, Fig. 4 is an illustration of the machined hole, and Fig. 5 is the Fig. 6 is a drawing of the same finishing process, Fig. 7 is a cutting process drawing of the same method, Fig. 8 is a drawing of the preliminary processing of the second processing method, Fig. 9 is a drawing of the finishing process, Fig. 10 is a cutting process diagram of the same method, Fig. 11 is a preliminary machining diagram of the third processing method, Fig. 12 is a finishing machining diagram of the same method, and Fig. 13 is a diagram of the cutting process of the same method.
The figure is a cutting process diagram of the same method, Figure 14 is a preliminary machining diagram of the fourth machining method, Figure 15 is a finishing machining diagram of the same method, Figure 16 is a cutting process diagram of the same direction, and Figure 17 is a diagram of the conventional step. It is a diagram of an attached end mill. I・Shank 2・・Small diameter cutting edge portion・Large diameter cutting edge portion bottom edge

Claims (3)

[Claims] (1) A small-diameter cutting edge is provided at the tip of the tool, and a large-diameter cutting edge is provided axially apart from the small-diameter cutting edge, and each blade consists of one blade, and its edge line is discontinuous with each other. A stepped end mill characterized by being formed on the opposite side to the center. (2) The stepped end mill according to claim 1, wherein the bottom edge of the small diameter cutting edge section is formed up to the center of rotation, and the bottom edge of the large diameter cutting edge section is formed up to the inner side of the cutting edge diameter of the small diameter cutting edge section. (3) In the method of drilling stepped holes or through holes in a resin plate using a stepped end mill that has a small-diameter cutting edge and a large-diameter cutting edge, the small-diameter cutting edge is drilled into the resin plate as a preliminary process prior to drilling. Cut a small long hole to a length that is greater than or equal to the radius of the large diameter cutting edge and less than or equal to the major axis of the hole (or diameter if it is a circular hole).
After the large-diameter cutting blade further penetrates or penetrates the elongated hole by a predetermined amount, cutting is performed with the large-diameter cutting blade along the elongated hole or further beyond the length of the elongated hole to form a stepped hole or A resin board hole drilling method characterized by forming a through hole.