JPH0650086Y2 - Recess bowling bite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a recess boring tool, particularly to a recess boring tool used for cutting an inner surface of a cylinder having a small diameter and a long length.

[Prior Art] Conventionally, when cutting the inner surface of a small diameter and long cylinder,
A recess boring bar as shown in the figure or a normal boring bar has been used. As shown in FIG. 4, the recess boring bar has a shank 11 as an axis, and a boring bar portion 12 and cutting edge portions 16 and 17 are cylindrically ground, and then a surplus portion is ground and removed as shown in FIG. Grind the rake face 15 slightly lower than the axial center. The recess boring bar manufactured in this way is used by rotating the shank 11 so that the rake angle α is appropriate (about 7 °) as shown in FIG. This bit is scooped 15
The original specifications of the cutting edge can be maintained only by surface grinding, and there is an advantage that re-polishing is easy.

[Problems to be solved by the invention] When cutting the inner surface of a small diameter and long cylinder using the conventional recess boring tool described above, the inner diameter is 1 to 3 mm.
When the ratio (L / D) of the length (L) to the inner diameter (D) exceeds 5, chattering occurs in the cutting tool, which makes it difficult to perform accurate machining. This phenomenon is caused by the fact that the diameter of the boring bar portion cannot be increased because the shank of the bite, the boring bar portion and the cutting edge portion are formed coaxially, and the rigidity of the boring bar portion becomes insufficient.

Also, when processing the above members using a normal boring bar, the diameter of the boring bar can be increased,
There is a drawback that the cutting edge specifications change with each re-polishing.

An object of the present invention is to provide a recess boring bar having high rigidity while maintaining the advantage of the recess boring bar that can be easily re-ground.

[Means for Solving the Problems] In order to achieve the above object, the first invention of the present application provides a shank for mounting a bite, a columnar boring bar portion extending from the shank, and a tip end portion of the boring bar portion. The cutting edge portion, the cutting edge portion, the cross-sectional shape of the cutting edge front relief portion of the cutting edge portion in the cutting edge surface orthogonal to the direction in which the axis of the boring bar portion of the boring bar portion extends in a direction perpendicular to the cutting edge surface. A recess for cutting the inner peripheral surface of the workpiece, which has an arcuate shape centered on the extending blade tip axis, and has the same cross-sectional shape of the blade tip relief portion in a plane including the blade tip axis. In the boring bar, the axis of the boring bar portion is provided in a relationship that coincides with the axis of the inner peripheral surface of the work at the time of starting the cutting of the inner peripheral surface of the workpiece, and the axis of the cutting edge portion is the It is characterized in that the blade surface is formed in an eccentric relationship with the axis of the boring bar.

In addition to the first invention, the second invention of the present application further has an eccentric amount i between the axis of the boring bar and the axis of the cutting edge. It is characterized by being defined in.

Further, a third invention of the present application is in addition to the first invention or the second invention, and further, a shank shaft center of the shank,
It is characterized in that it is provided so as to coincide with the axis of the cutting edge portion.

[Operation] When cutting the inner peripheral surface of the work, make sure that the center of the inner peripheral surface of the work and the center of the boring bar of the boring bar are aligned with the center of the cutting edge. Since it is eccentric with respect to it, the diameter of the boring bar portion can be increased without interfering with the inner diameter of the work by that amount, the rigidity of the boring bar portion is improved, and chattering can be prevented.

[Embodiment] An embodiment of the recess boring tool of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a plan view and a side view of a cutting edge side of a recess boring tool of the present invention, and FIG. 2 is a sectional view taken along the line AA of the work and the cutting tool in FIG. As shown in FIGS. 1 and 2, the recess boring bar of the present invention has a boring bar portion having a boring bar portion axis b which is eccentric to the shank axis a of the shank 1 by i as shown in FIGS. 2, the cutting edge portion 3 is formed at the tip of the boring bar portion 2, and the cutting edge front clearance portion 8 of the cutting edge portion 3 in FIG. 2 has an arc shape, and the arc center thereof (hereinafter referred to as the cutting edge axis). ) Has the same axis as the shank axis a. The cutting edge portion 3 is ground so as to form a flat surface 4 including the shank axis a, and the shank axis a
The cutting edge rake face 5 is formed by further grinding by h from the flat surface 4 including. After the cutting edge rake face 5 is formed, the excess thickness on the side opposite to the cutting edge is ground and removed to make it approximately the same as the boring bar portion 2 as shown in FIG.

More specifically, a method of manufacturing a recess boring bar suitable for a work inner diameter of 1.5 mm will be described with reference to FIGS. 2 and 7. First of all, the rake angle α and the front clearance angle β of the cutting edge are α = 7 ° and β = 10 °, respectively.
And set.

The relationship between the radius R of the front relief portion 8 around the shank axis a and the grinding cut-down dimension h of the rake face 5 is h / R = sin
(Α + β), so if α = 7 ° and β = 10 °, then h / R = sin17 ° = 0.292.

If R is set to 0.85 (mm), h will be 0.25 (mm). The size of R is set in consideration of maintaining a suitable clearance between the front relief 8 and the inner surface of the work.

Next, the eccentricity i of the boring bar portion axis b of the boring bar portion 2 with respect to the shank axis a is calculated. Eccentricity i
Is the inner radius Rw of the workpiece, the front clearance angle β, and the front edge clearance radius R, the following relationship is established.

Substituting R = 0.85, Rw = 0.75 and β = 10 ° into the above equation gives i = 0.17.

After setting the above specifications, as shown in Fig. 7 (1), the boring bar part 2 is ground around the boring bar part axis b which is eccentric to the shank axis a by i (0.17 mm). To do.

Next, as shown in FIG. 7 (2), the flanks 6 and 7 of the cutting edge portion 3 are ground around the shank axis a, and then, as shown in FIG. 7 (3), with respect to the shank axis a. The plane 4 is fixed so that the position of the axis b of the boring bar is Rsin (α + β) -Rwsinα (0.157mm) on the X-axis side and Rcos (α + β) -Rwcosα (0.068mm) on the Y-axis side. Grinding and cutting edge rake face 5 h (0.25m
m) Only the ground is cut down. Finally, the non-cutting edge side surplus of the cutting edge portion 3 is ground and removed.

When cutting a small diameter long cylinder using the recess boring bar manufactured as described above, raise the shank axis a, which coincides with the cutting edge axis, by 0.157 mm from the cutting point and scoop around the shank axis a. If you set it by rotating it by an angle α (7 °), you can set a rake angle of 7 ° and a front clearance angle of 10 °. By doing so, as shown in FIG. 2, the work inner diameter and the axial center of the boring bar portion 2 can be made to substantially coincide with each other, so that the clearance between the work inner diameter and the boring bar portion 2 becomes uniform over the entire circumference, and the boring bar portion The diameter of the part 2 can be maximized.

[Effects of the Invention] As described above, the recess boring bar of the present invention makes sure that the axis of the inner peripheral surface of the work is aligned with the axis of the boring bar when the inner peripheral surface of the work is cut. Since the axis of the boring bar is eccentric with respect to the center, it is possible to increase the diameter of the boring bar (thus, the cross-sectional area in the cross section orthogonal to the axis of the boring bar) without interfering with the inner diameter of the work. The rigidity of
It enables cutting without chattering.

Further, since the advantage of the recess bite is maintained, the re-polishing does not change the specifications of the cutting edge, and the re-polishing is easy.

[Brief description of drawings]

FIG. 1 is a plan view of a recess boring tool of the present invention and a side view of the cutting edge side, FIG. 2 is a sectional view taken along the line AA of the work and the cutting tool in FIG.
The figure is a plan view of a conventional recess boring tool, Figures 4 and 5 are diagrams showing the manufacturing process of a conventional recess boring tool, and Figure 6 is a workpiece and a blade of a conventional recess boring tool when cutting the inner surface of a small diameter cylinder. FIG. 7 is a sectional view showing the process of manufacturing the recess boring bar of the present invention. [Explanation of symbols for main parts] 1: Shank, 2: Boring bar part, 3: Cutting edge part, 5: Cutting edge rake face

Claims (3)

[Scope of utility model registration request] 1. A shank for mounting a bite, a columnar boring bar portion extending from the shank, and a cutting edge portion provided at a tip portion of the boring bar portion, the cutting edge portion of the boring bar portion. The cross-sectional shape of the cutting edge front relief portion of the cutting edge portion in the cutting edge surface orthogonal to the extending direction of the boring bar portion axial center is an arc shape centering on the cutting edge portion axial center extending in the direction perpendicular to the cutting edge surface, and, In a recess boring tool for cutting the inner peripheral surface of a workpiece, in which the cross-sectional shape of the front edge relief portion is formed in the plane including the blade edge axial center, the boring bar axial center is the inner peripheral surface of the workpiece. At the time of the start of cutting, it is provided in a relationship that coincides with the axial center of the inner peripheral surface of the workpiece, and the axial center of the cutting edge is eccentric to the axial center of the boring bar at the cutting edge surface. Recess boring tool, characterized in that was. 2. The eccentricity i between the axis of the boring bar and the axis of the cutting edge is However, R is a front relief radius of a cutting edge, β is a front relief angle, and Rw is defined by an inner radius of a work, The recess boring bit according to claim 1. 3. The recess boring bar tool according to claim 1, wherein a shank shaft center of the shank and the cutting edge part shaft center are provided so as to coincide with each other.