JPH0230175Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] This invention relates to a milling tool in which a throw-away tip is attached to the outer periphery of a tool body that is rotated about an axis. [Prior Art] In recent years, milling tools such as end mills that have one or more throw-away chips (hereinafter referred to as chips) removably attached to the outer periphery of the tool body have been increasingly used. be. 4 to 6 show a conventional milling tool of this kind, and reference numeral 1 in the figures indicates the tool body of this milling tool. This tool body 1 has a cylindrical shape whose base end is rotatably held around an axis by a drive source (not shown), and diametrically symmetrical positions on the outer periphery of the tip end are each axially rotated. A plurality of concave chip attachment portions 2 (two in the figure) are formed along the same line at equal intervals so as to alternate with each other. A portion of the tool main body 1 is largely cut out on the tip end side of each of the tip attaching parts 2 in the rotational direction, and chip pockets 3, 3 are formed which are continuous with the tip attaching parts 2. As a result, the tip attaching portion 2 includes a tip attaching seat 4 facing the outer circumferential direction of the tool body 1, a tip locking surface 5 facing the rotational direction, a tip positioning surface 6 facing the axial direction, and a tip retaining surface 5 facing the rotation direction. 6 is formed. And, in the chip mounting part 2...
Each tip 7... is a clamp screw (not shown)
It is removably attached. This chip 7 has a rectangular plate shape with upper and lower surfaces 8 and 9 parallel to each other, and its lower surface 9 is brought into contact with the chip mounting seat 4 of the chip mounting section 2, and the chip 7 is formed on the ridge of the upper surface 8. The cutting blade 10 is attached to the tip mounting portion 2 so as to protrude radially outward from the outer periphery 1a of the tool body 1 by a dimension indicated by _N1 in FIG. By the way, in the above-mentioned conventional milling tool, if the above-mentioned protrusion amount _N1 of the cutting edge 10 of the chip 7 with respect to the outer circumference 1a of the tool body 1 is increased as it is, the force applied to the cutting edge 10 increases in proportion to this, As a result, the seating rigidity of the tip 7 deteriorates, and in addition, it is necessary to increase the rigidity of the tip 7 in a direction perpendicular to the radial direction of the tool body 1.
Therefore, the protrusion amount N ₁ of the cutting edge 10 is usually 1
It was set at ~2mm. [Problems to be solved by the invention] However, in the conventional milling tool described above, since the protrusion amount _N1 of the cutting edge 10 of the chip 7 is small, as shown in FIG. When the feed amount Sz of the cutting blade 10 is increased, the gap 12 between the outer periphery 1a of the tool body 1 and the workpiece 11 becomes small, so if chatter or vibration occurs in the tool body 1, the above-mentioned There was a problem that the tool body 1 and the workpiece 11 interfered with each other. In addition, since the chips to be discharged tend to get caught in the gap 12, there is a problem in that the chip 7 is easily damaged. [Purpose of the invention] This invention was made in view of the above circumstances.
It is an object of the present invention to provide a milling tool which is free from interference between the tool body and the workpiece even if chatter or vibration occurs during cutting, and which has excellent chip evacuation performance. [Means for solving the problem] The milling tool of this invention has a chip on the outer periphery of a cylindrical tool body that is rotated about an axis, with its cutting edge positioned on the outer periphery side of the tool body. The difference N between the turning radius R ₁ of the cutting edge of the chip and the radius R ₂ of the outer periphery of the tool body of the attached milling tool is set to R ₁ /8≦N≦R ₁ /4, and further The thickness T of the chip in a direction orthogonal to the radial direction of the tool body is T≧2.4×N. [Example] Figures 1 to 3 show an example of a milling tool of this invention, and parts common to those shown in Figures 4 to 6 are denoted by the same reference numerals. The explanation will be omitted. 1 to 3, in this milling tool, chips 20 are removably attached to the chip attachment portions 2 of the tool body 1, respectively. Here, each of the tips 20 has a cutting edge 22 formed on the ridge of the upper surface 21 of the tip 20 at the outer periphery of the tool body 1.
It is mounted so as to protrude outward in the radial direction from a by a dimension indicated by N in FIG. In this milling tool, the protruding amount N of the cutting edge 22 of the tip 20 is set to be 1/8 or more and 1/4 or less of the rotation radius R ₁ of the cutting edge 22, and The thickness T in the direction orthogonal to the radial direction of the tool body 1 at the cutting edge 22 position is set to be 2.4 times or more the above-mentioned protrusion amount N. That is, to give a concrete example, in a milling tool with a tip rotation radius of 24 mm, the protrusion amount N of the cutting edge of the tip from the outer periphery of the tool body is 3.
If the thickness T at the cutting edge of the chip is within the range of 5 mm or more and 6 mm or less, for example, if the protrusion amount N is set to 5 mm, then 5 x 2.4 = 12 mm.
It is set to be the above. Here, if the thickness T of the cutting edge 22 of the tip 20 is less than 2.4 times the protrusion amount N,
Tip 2 that comes into contact with tip mounting seat 4 of tool body 1
It is not possible to obtain a sufficient area of the lower surface 23 of 0,
As a result, the holding force due to the friction between the chip 20 and the chip mounting seat decreases, and the seating rigidity of the chip 20 deteriorates, and the rigidity of the chip 20 in this direction becomes insufficient, which is inappropriate. Also,
The above protrusion amount N of the cutting edge 22 of the chip 20 is defined as the cutting edge 22
If the rotation radius R is less than 1/8 of ₁ , it will not be possible to obtain a sufficient clearance between the outer periphery 1a of the tool body 1 and the workpiece 11, and on the other hand, the protrusion amount N will be reduced by the rotation of the cutting blade 21. If the radius R exceeds _1/4 , the thickness T of the tip 20 will increase too much corresponding to this protrusion amount N, and the shape of the tip attachment part 2 of the tool body 1 will become too large, reducing the strength of the tool body 1 itself. They are unsuitable because they deteriorate and the chip 20 itself becomes large and expensive, making it uneconomical. Therefore, in the case of such a milling tool, the difference N between the radius of rotation R1 of the cutting edge 22 of the attached chip ₂₀ and the radius _R2 of the outer periphery 1a of the tool body 1 is calculated as ₁ of the radius of rotation R1. Since the gap is set to be 1/8 or more and 1/4 or less, a large gap 25 can be obtained between the tool body 1 and the workpiece 11. Therefore, even if the feed rate Sz is increased and chatter or vibration occurs in the tool body 1, there is no risk that the tool body 1 and the workpiece 11 will interfere with each other, and the gap 25 is further widened. Chips can be smoothly discharged through the Moreover, since the thickness T in the direction orthogonal to the radial direction of the tool body 1 at the position of the cutting edge 22 of the tip 20 is set to be more than 2.4 times the protrusion amount N, the force applied to the tip 20 increases. Also, in proportion to this, the lower surface 23 of the chip 20
This results in an increase in the contact area between the tool body 1 and the tip mounting seat 4 of the tool body 1. Therefore, tip 20
Since the holding force of the tip 20 due to the frictional force between the lower surface 23 of the tool body 1 and the tip mounting seat 4 of the tool body 1 increases, there is no fear that the seating rigidity of the tip 20 will deteriorate. Furthermore, the chip thickness T is the cutting edge protrusion amount N
For example, as shown in FIG.
If it is fixed at 0, the tip 2
0 retention force increases. That is, in FIG. 7, the distance t from the cutting edge 22 to the end of the clamp screw 30 is constant (for example, 10
mm), the maximum outer diameter of the head of the clamp screw 30 that can be embedded in the chip 20 is (T-2t). However, in this embodiment, since the tip thickness T increases in accordance with the cutting edge protrusion amount N, the outer diameter of the clamp screw 30 that can be used increases accordingly, and as a result, the holding force of the tip increases depending on the cutting edge. The deterioration of the seating rigidity of the chip, which increases in proportion to the amount of protrusion N, can be more reliably avoided. Here, in order to clarify the effects of the present invention, a first cutting test was carried out in which cutting was carried out while changing the cutting edge protrusion amount N as appropriate, and a second cutting test was carried out in which cutting was carried out while changing the chip thickness T as appropriate. I did this. The contents and processing conditions of each test are as shown below, and the results are shown in Tables 1 and 2. (First cutting test) In order to compare the difference in the cutting situation due to the difference in the protrusion amount N of the cutting edge, cutting was performed while changing the protrusion amount N of the cutting edge as appropriate under the following processing conditions, and each setting of the protrusion amount N was Regarding the value, we inspected the tool body, damage to the cutting edge, vibration during cutting, and condition of the machined surface. - Cutting speed...120mm/min - Workpiece feed rate...250mm/min - Tool feed rate per tooth...0.31mm - Tool outer diameter...48mm - Change range of cutting edge protrusion N...1.5 ,3.0,6.0,
4 stages of 7.0mm Chip thickness T...2.4N Cutting surface dimensions...Tool axis direction 40mm x Workpiece feed direction 300mm Cutting depth and number of cuts...5mm x 10 times Workpiece material... ...SCM440 (Hardness H _B 220) (Second cutting test) In order to compare the difference in chip seating rigidity due to the difference in chip thickness T, cutting was performed while changing the chip thickness T as appropriate under the following processing conditions. The number of cuts until defects such as chip breakage occurred was measured.・Cutting blade protrusion amount N...3.0mm ・Change range of chip thickness T...2.0N, 2.4N,
Three stages of 5.0N Other machining conditions were the same as in the first test above, except for the number of cuts. In all tests, the tip was attached to the tool body by screwing in a clamp screw from the outer circumferential side of the tool.

【table】

【table】

[Table] As is clear from Table 1, the cutting edge protrusion amount N satisfies R ₁ /8≦N≦R ₁ /4 with respect to the rotation radius R ₁ of the cutting blade, that is, under the above processing conditions.
No damage to the tool periphery or cutting edge was observed in the range of 3.0 mm to 6.0 mm. Also, the protrusion amount N is
In the case of 6.0 mm, a negligible level difference was observed on the machined surface. Therefore,
The upper limit of the protrusion amount N is 6.0mm,
If the protrusion amount N is increased beyond this, the difference in level will increase to an extent that cannot be ignored, which is not preferable. On the other hand, when the cutting edge protrusion amount N is set to a range less than R _1/8 (1.5 mm), damage to the tool periphery is observed as a result of interference between the tool periphery and the workpiece material, and chip evacuation is reduced. It has become clear that damage to the cutting edge is also induced by deterioration of the properties. Furthermore, it was confirmed that when the cutting edge protrusion amount N was set to a range exceeding R ₁ /4 (7.0 mm), the seating rigidity of the chip was insufficient and the cutting edge was likely to be damaged. Furthermore, as is clear from Table 2, in the range where the chip thickness T is less than 2.4 times the cutting edge protrusion N,
The chip breaks at the initial stage after only 8 cuttings, and cutting is almost impossible. On the other hand, when the chip thickness T is 2.4N, minute chipping only occurs after 29 cuttings, and when the chip thickness T is 5.0N, the number of cuttings is 50. It was confirmed that stable cutting could still be performed without chipping or the like even when the cutting speed was exceeded. This is presumed to be because when the chip thickness T is set within the above range, deterioration of the chip seating rigidity is effectively prevented by increasing the chip seating area and expanding the clamp screw diameter. From the above results, in order to prevent interference between the tool body and the workpiece material and perform smooth cutting while ensuring the seating rigidity of the chip, the cutting edge protrusion amount N should be set to R ₁ /8 ~
It has been confirmed that it is meaningful to set the chip thickness T to 2.4N or more while setting it within the range of R ₁ /4. [Effects of the invention] As explained above, the milling tool of this invention has a chip on the outer periphery of a cylindrical tool body that is rotated about an axis, with its cutting edge positioned on the outer periphery of the tool body. The difference N between the turning radius R ₁ of the cutting edge of the chip and the radius R ₂ of the outer periphery of the tool body of the attached milling tool satisfies R ₁ /8≦N≦R ₁ /4, and the above The thickness T of the chip in the direction perpendicular to the radial direction of the tool body is T≧2.4×N. Therefore, with this milling tool, even if chatter or vibration occurs during cutting, there is no risk of interference between the tool body and the workpiece, and excellent chip evacuation performance can be obtained. Furthermore, when the chip is attached to the tool body using a clamp screw that is twisted from the outer circumference of the tool, it is possible to embed a larger diameter clamp screw without sacrificing chip rigidity as the seating area of the chip is expanded. Therefore, the chip holding force can be further increased and deterioration of the chip seating rigidity can be more reliably prevented.

[Brief explanation of the drawing]

Figures 1 to 3 show an embodiment of the milling tool of this invention, where Figure 1 is a front view, Figure 2 is a side view, and Figure 3 shows the state of cutting by the milling tool. Figures 4 to 6 show a conventional milling tool, where Figure 4 is a front view, Figure 5 is a side view, and Figure 6 is a diagram showing the state of cutting by the conventional milling tool. It is. FIG. 7 is a diagram showing a state in which a chip is attached using a clamp screw in the milling tool of the present invention. DESCRIPTION OF SYMBOLS 1...Tool body, 1a...Outer periphery, 2...Tip mounting portion, 3...Tip pocket, 4...Tip mounting seat, 7, 20...Throwaway tip (chip), 8, 21...Top surface, 9 , 23...bottom surface, 1
0,22... Cutting blade, 11... Cutting material, 12,2
5... Gap, T... Chip thickness, R, R ₁ ... Cutting edge rotation radius, R ₂ ... Radius of tool body outer periphery, N...
...Protrusion amount of cutting edge, Sz...Feed amount.

Claims (1)

[Scope of Claim for Utility Model Registration] A milling tool in which a throw-away tip is attached to the outer periphery of a cylindrical tool body that rotates about an axis with its cutting edge positioned on the outer periphery of the tool body. , the rotation radius of the cutting edge of the throw-away tip R ₁ and the radius of the outer circumference of the tool body R ₂
The difference N between _{the two} and , T≧2.4×N.