JPH0647619A - Reamer with sub-land - Google Patents

Abstract

PURPOSE:To shorten extremely the length between a first blade for roughing and a second blade for finishing, provide a long regrinding length, minimize processing residual, improve chamferring performance of the first blade, and improve accuracy of finishing face. CONSTITUTION:A reamer is provided with two lines of first chip discharge grooves 11, a second chip discharge groove 12 in the outer circumference of the land between them, and a sub-land having an outside diameter smaller than that of the land between the first and the second chip discharge grooves 11, 12. A second blade 17 for finishing which is located on the base end side of a first blade 15 is provided in the second chip discharge groove 12. And the outer circumferencial part of the sub-land is formed into an eccentric relief 19 which is gradually closer to the internal circumferencial side as it approaches from the tip edge rearward and a radial step difference between the first blade 15 and the second blade 17 is set to 0.02-0.5mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a reamer with a subbrand having a multistage cutting edge.

[0002]

2. Description of the Related Art Conventionally, a step reamer shown in FIGS. 7 and 8 is known as a reamer having a multistage cutting edge. This reamer has a chip discharge groove 2 formed on the outer periphery of a tool body 1 composed of a large diameter portion 1a and a small diameter portion 1b, and a first cutting edge on the outer peripheral edge of the wall surface of the chip discharge groove 2 facing the rotation direction. 3. The second cutting edge 4 is formed on the step portion between the large diameter portion 1a and the small diameter portion 1b, and the margin 5 forming a cylindrical curved surface is further formed on the outer peripheral portion continuous with the chip discharge groove 2. Here, the margin 5 is formed by cylindrical grinding that grinds while rotating the reamer around the axis using the outer circumference of the disk-shaped grindstone. In such a reamer, since the rough cutting is performed by the small-diameter first cutting edge 3, the finishing is performed by the large-diameter second cutting edge 4, and the burnishing is performed by the margin of the large-diameter portion 1a, the finished surface accuracy is high. Also, there is an advantage that the machining efficiency is good because the machining allowance is large.

[0003]

However, in the reamer as described above, the second cutting edge of the large diameter portion is continuous with the margin of the small diameter portion. The small-diameter portion has a portion that is moved backward toward the rear end and has no margin for the length of the backward movement. For this reason, the re-polishing of the cutting edge can be performed up to about half the length of the small diameter portion at most. Further, in the above reamer, the small diameter portion cannot be formed unless the length of the small diameter portion is at least 2 to 3 mm because of the rounded corners of the grindstone. For this reason, when processing a blind hole, a small-diameter portion, which is not finished by the second cutting blade, remains at the bottom of the hole by 2 to 3 mm. Furthermore, since the margin of the small diameter part is also composed of a cylindrical curved surface,
When the first cutting edge bites into the work material, there is a problem that overburning is likely to occur, and the large cutting torque at that time deteriorates the surface roughness and, in some cases, breaks the reamer.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the above-mentioned conventional reamer, and the length of the small diameter portion can be shortened as much as possible, so that the unprocessed residue can be minimized. Along with being able to take a long re-polishing length, it also prevents overburning,
It is an object of the present invention to provide a reamer capable of improving finish surface accuracy.

[0005]

A reamer of the present invention is provided with two first chip discharge grooves in a tool body which is rotated around an axis, and second chip chips are provided on an outer peripheral portion of a land between the first chip discharge grooves. A discharge groove is provided, a sub-brand having an outer diameter smaller than that of the land is provided between the first and second chip discharge grooves, and rough machining is performed on the outer peripheral side of the tip edge of the wall surface facing the rotation direction of the first chip discharge groove. A first cutting edge is provided, and a second cutting edge for finishing, which is located closer to the base end side than the first cutting edge, is provided on the outer peripheral side of the wall surface facing the rotation direction of the second chip discharge groove. Is an eccentric relief that gradually becomes closer to the inner circumferential side with respect to an imaginary circle forming the diameter of the outer circumferential portion as it goes rearward from the leading edge in the rotational direction, and the radius of the first cutting edge and the second cutting edge It is characterized in that the step in the direction is 0.02 to 0.5 mm.

[0006]

According to the present invention, the roughing first cutting edge is provided on the sub-brand, so that the distance between the first cutting edge and the second cutting edge can be set arbitrarily. Therefore, the re-polishing length can be increased. In addition, since the outer peripheral portion of the sub-brand has an eccentric relief, overburning does not occur. Further, the reason for the above numerical limitation is that if the step is less than 0.02 mm and the surface roughness of the roughened cutting surface is rough, the processed surface remains on the finished surface,
This is because if it exceeds 0.5 mm, the load of finish processing becomes high and desired finish surface accuracy cannot be obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to. FIG. 1 is a side view showing a reamer of the embodiment, and reference numeral 10 shows a tool body. Tool body 1
In the outer peripheral portion of 0, two first twist grooves (first chip discharge grooves) 11 having a large cross-sectional area and deep are formed, and the first twist groove 1
A second twisted groove (second chip discharge groove) 12 having a small cross-sectional area and shallow is formed between the two. Also, the first
A land 13 that forms the outer diameter of the reamer is formed in a portion of the twisted groove 11 that is located in the rotation direction.
A subland 14 having a diameter smaller than that of the land 13 is formed in a portion located in the rotational direction of 2.

Further, a first cutting edge 15 for rough machining is formed on the outer peripheral side of the tip edge of the wall surface of the first spiral groove 11 which faces the direction of rotation. The biting angle α formed by a plane orthogonal to the tool axis of the first cutting edge 15 is set to 0 to 45 °. On the other hand, a small diameter portion 16 having a smaller diameter than the rear end side is formed on the outer peripheral portion on the front end side of the sub-brand 14. A second cutting edge 17 for finishing, which has a diameter larger than that of the first cutting edge 15, faces the rotation direction of the second spiral groove 12 at a step portion between the small diameter portion 16 and a portion on the base end side thereof. It is formed along the ridgeline of the wall surface. First
The radial step between the cutting edge 15 and the second cutting edge 17 is 0.02.
It is set to 0.5 mm. Further, the biting angle β of the second cutting edge 17 is set to 15 to 85 ° as shown in FIG. 3, and α <β.

The reason for α <β is to reduce the biting angle α of the first cutting edge 15 to reduce the radial component force of the cutting resistance, thereby preventing the reamer from swinging. Also,
The cutting edge length is increased by increasing the biting angle β of the second cutting edge 17,
This is because wide and thin chips can be generated to improve the finished surface roughness. In addition, the difference between the first cutting edge 15 and the second cutting edge 17 in the radial direction is 0.02 to 0.
5 mm means that if it is less than 0.02 mm, if the surface roughness of the roughened cutting surface is rough, the processed surface remains on the finished surface, and if it exceeds 0.5 mm, the load of finishing processing becomes high. This is because the desired finished surface accuracy cannot be obtained.

Further, a margin 18 is formed on the outer peripheral portion of the land 13. The margin 18 is formed by cylindrical grinding, and has an outer circumference of a cylindrical curved surface. On the other hand, an eccentric relief 19 is formed on the outer peripheral edge of the subland 14 in the rotational direction.
For example, as shown in FIG. 5, the eccentric relief 19 tilts the grindstone G toward the tip side of the tool T (for example, 30 °), and further tilts the end surface of the grindstone G along the twist direction of the tool T, for example, 30 °. Formed by grinding. As shown in FIG. 6, the eccentric relief 19 is a virtual circle O that constitutes the outer diameter of the subland 14.
On the other hand, it is configured by a flank that gradually becomes closer to the inner circumferential side with respect to the virtual circle O as it goes rearward from the tip edge in the rotation direction (arrow X).

The reamer having the above construction is used for finishing a prepared hole that has been machined in advance. When processing, first
The cutting edge 15 bites into the edge of the hole for rough processing. In this case, since the outer peripheral portion of the sub-brand 14 is constituted by the eccentric relief 19, overburnishing does not occur, and rough skin of the hole and breakage accident can be prevented in advance. Further, since the biting angle α of the first cutting edge 15 is small, the radial component force of the cutting resistance is small,
Moreover, since the eccentric relief 19 is formed, the biting property is dramatically improved. Next, the second cutting edge 1
7 bites to finish cutting and burnishing is performed by the margin 18. In this case, since the biting angle β of the second cutting edge 17 is large, the cutting edge length is long, whereby wide and thin chips are generated and the finished surface roughness is improved. Further, in this reamer, since the first cutting edge 15 is arranged on the sub-brand 14, it is possible to obtain a desired machined hole shape by reducing the distance between the first cutting edge 15 and the second cutting edge 17. Needless to say, the re-polishing length can be increased. Further, in this reamer, since the step difference between the first cutting edge 15 and the second cutting edge 17 in the radial direction is 0.02 to 0.5 mm, even if the surface roughness of the roughened cutting surface is rough, Since the processed surface does not remain and the load of finishing processing does not increase, a desired finished surface accuracy can be obtained. The present invention is not limited to the one having the twist groove as described above, and may be a linear chip discharge groove.

[0012]

As described above, in the reamer of the present invention, the tool body rotated about the axis is provided with the two first chip discharging grooves, and the first chip discharging grooves are provided with the first chip discharging grooves at the outer periphery of the land. 2 Chip discharge grooves are provided, a sub-brand having an outer diameter smaller than the land is provided between the first and second chip discharge grooves, and rough machining is performed on the outer peripheral side of the tip edge of the wall surface facing the rotation direction of the first chip discharge groove. And a second cutting edge for finishing, which is located closer to the base end side than the first cutting edge, on the outer peripheral side of the wall surface facing the rotation direction of the second chip discharge groove. The outer peripheral portion of the sub-brand is an eccentric relief that gradually becomes closer to the inner peripheral side with respect to a virtual circle forming the diameter of the outer peripheral portion as it goes rearward from the leading edge in the rotational direction, and also has a first cutting edge and a second cutting edge. The step in the radial direction of 0.02 to 0.5 mm
Therefore, it is of course possible to reduce the distance between the first cutting edge and the second cutting edge to obtain a desired shape of the processed hole, and further, to increase the re-polishing length. Over-burning does not occur during processing by
It is possible to prevent rough skin of the hole and breakage accidents, improve the biting property of the first cutting edge, and even if the surface roughness of the roughened cutting surface is rough, Since the machined surface does not remain and the load of the finishing process does not increase, it is possible to obtain a desired finished surface accuracy.

[Brief description of drawings]

FIG. 1 is a bottom view of a reamer with a subland according to an embodiment of the present invention.

FIG. 2 is a front end view in the axial direction of the reamer with a subland shown in FIG.

FIG. 3 is a front view of a second cutting edge.

FIG. 4 is a cross-sectional view of the reamer with sub-brand shown in FIG.

FIG. 5 is a side view showing a state where eccentric relief grinding is performed.

FIG. 6 is a cross-sectional view showing an eccentric relief of the reamer with sub-brand shown in FIG.

FIG. 7 is a side view showing a conventional step reamer.

8 is a front view of the step reamer shown in FIG. 7 in the axial direction.

[Explanation of symbols]

 10 Tool Body 11 First Twisted Groove (First Chip Ejection Groove) 12 Second Twisted Groove (Second Chip Ejection Groove) 14 Sabrand 15 First Cutting Edge 17 Second Cutting Edge 19 Eccentric Relief

Claims (3)

[Claims] 1. A tool main body which can be rotated about an axis,
The first chip discharge groove of the strip is provided, the second chip discharge groove is provided on the outer peripheral portion of the land between the first chip discharge grooves, and the outer diameter is smaller than the land between the first and second chip discharge grooves. A sub-brand is provided on the outer peripheral side of the tip end edge of the wall surface facing the rotation direction of the first chip discharge groove, and a first roughing cutting edge is provided on the outer peripheral side of the wall surface facing the rotation direction of the second chip discharge groove. A second cutting edge for finishing, which is located closer to the base end side than the first cutting edge, is provided. Further, the outer peripheral portion of the sub-brand has a diameter of the outer peripheral portion as it goes rearward from the leading edge in the rotational direction. The eccentric relief gradually becomes closer to the inner circumference side with respect to the imaginary circle, and the step in the radial direction between the first cutting edge and the second cutting edge is 0.02 to 0.5 mm. Branded reamer. 2. The savrand according to claim 1, wherein the biting angle formed by the first cutting edge with a plane orthogonal to the axis is set to be smaller than the biting angle of the second cutting edge. Reamer with. 3. The reamer with a subland according to claim 1, wherein the chip discharge groove has a spiral shape.