JPH03221303A - Boring bar - Google Patents

Abstract

PURPOSE:To constrain the chattering vibration of the tool main body by closing an open part by a screw member with the filling of a granular body in the hollow barrel part of the tool main body inside of a boring bar for a lathe, and fixing the ratio of the sectional area of the hollow barrel part to that of the tool main body in a specified range. CONSTITUTION:A lot of small balls(granular body) 11 are filled in the hollow part 10 formed at the inner part of a tool main body 1 and sealed by the plug screwed with the base of the follow part 10. Also, the ratio (A1/A2) of the sectional area A1 on the tool shaft orthogonal section of the hollow part 10 to the sectional area A2 of the tool main body 1 including the hollow part 10 is preferably fixed so as to become in the range of 0.06 - 0.36. Moreover, with respect to the position of the hollow part 10, it is perferable to provide eccentricity to the side part 1a of one part of the tool main body 1 where a tip 7 is provided and to the side part 1b of the other part of the tool main body 1 opposed by interposing a tool shaft center PO in the tool front face view.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a boring bar used for boring a workpiece in a lathe, and more particularly to a boring bar with excellent vibration damping properties.

[Prior Art 1] It is known that in a boring bar used for boring with a lathe, the magnitude of the vibration damping rate of the tool body greatly affects machining accuracy, inner surface roughness, etc.

By the way, as a boring bar that increases the damping rate of such vibrations, a so-called sandwich structure boring bar in which a damping alloy such as a silent alloy is sandwiched between cemented carbide metals has been proposed. It has been confirmed that superior vibration suppression effects can be obtained compared to boring bars made of cemented carbide.
Hiroshi Kitajima, Yukio Tanaka, Jun Nakamura, Hiroshi Arimoto, “Improving the dynamic rigidity of a composite tool noyank using a damping alloy, 1 Precision Machinery, 53.10 (1987) 1582.”

[Problems to be Solved by the Invention] However, in the above-mentioned sandwich structure boring bar, the material cost of the damping alloy is high, and secondly, advanced technology is required to join the damping alloy and the cemented carbide. It also had the disadvantage of being bulky and expensive to manufacture.

The present invention was made against this background, and an object of the present invention is to provide a boring bar that has a high vibration damping rate, can effectively suppress chatter vibration, and is inexpensive.

[Means for Solving the Problems] The boring bar of the present invention has a structure in which a cavity opening to the outer surface of the tool body is formed inside the tool body, and this cavity is filled with granules. We are trying to resolve the above issues.

In this case, in order to optimize the vibration damping rate, it is effective to close the opening of the cavity to the outer surface of the tool body with a screw member.

Regarding the size of the cavity, the ratio of the cross-sectional area AI of the cavity in the cross section perpendicular to the axis of the tool body to the cross-sectional area A2 of the tool body including this cavity must be set within the following range. or suitable.

0.06 ≦ AI/A2 ≦ 0.36 Furthermore, the position of the cavity is such that when viewed from the front of the tool body, it is opposite to one side of the tool body where the cutting edge is provided across the tool axis. It is preferable to provide the tool body eccentrically toward the other side of the tool body.

[Function] According to the above structure, the energy of chatter vibration of the tool body is absorbed by friction between the granules filled in the cavity or between the granules and the inner wall of the cavity.

In this case, the vibration characteristics of the tool body can be adjusted by changing the packing density by changing the number and size of the granules, and furthermore, if the opening of the cavity is closed with a screw member. In addition, the vibration characteristics can also be changed by changing the amount of torsion of the screw member.

Embodiment J An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In these figures, reference numeral 1 is the tool body.

The tool body 1 is made of steel or cemented carbide, and has a blade portion 2, a neck 3, and a noyank 4 integrally molded in this order from the distal end to the proximal end.

Here, the upper part of the blade part 2 is cut out from the neck 3 toward the lower part toward the tool tip side, and the rake face 5 is cut out.
A chip mounting seat 6 is formed at its tip. In the tip mounting seat 6, a diamond-shaped indexable tip (hereinafter abbreviated as a tip) 7 made of cemented carbide is installed so that the nose of the cutting edge 8 protrudes from the outer periphery of the tip of the blade portion 2. It is removably attached with bolts 9 in the two state.

Further, inside the tool body 1, a cavity 10 is formed which is coaxial with the axis O of the tool body 1 and opens at the proximal end surface of the tool body 1. This cavity portion IO is formed in the shape of a circular elongated hole in a cross section perpendicular to the axis O, and its tip extends to the inside of the blade portion 2.

The cavity 10 is filled with a large number of small spheres (granules) 11 and sealed with a plug 12 screwed into the mouth of the cavity IO. Note that steel or cemented carbide is used as the material for these small balls 11.

Here, the cross-sectional area Al of the cavity 10 in the cross-section perpendicular to the tool axis, that is, the cross-sectional area of the small sphere may be determined as appropriate depending on the material of the workpiece, cutting conditions, etc., but if possible, the cross-sectional area A1 It is preferable to set the ratio (AI/A2) of the cross-sectional area A2 of the tool body 1 including the cavity IO to be in the range of 006 to 0.36. If AI/A2 is less than 0.06, there is a risk that there will be insufficient small balls and the vibration absorption effect described below will not be fully exerted.On the other hand, if AI/A2 exceeds 036, the actual cross-sectional area of the tool body l will be insufficient. This is because there is a risk that the tool rigidity will deteriorate.

In the boring bar configured as above, during cutting, the small balls 11 filled in the cavity lO or the small balls It and the empty lA+? Since the energy of chatter vibration generated in the tool body 1 is absorbed by the friction between the tool body 1 and the inner wall of the tool body 1, the vibration damping rate of the entire tool body 1 is improved.

Therefore, according to this embodiment, chatter vibration during cutting can be effectively suppressed and machining accuracy can be significantly improved.

In addition, since the boring bar of this embodiment has a simple structure in which the small balls 11 are confined in the cavity IO, it is extremely easy to manufacture, and is easier to manufacture than the above-mentioned sandwich structure boring bar. Costs can be significantly reduced.

In addition, according to this embodiment, vibrations can be absorbed by the small balls II made of steel or cemented carbide, so the material cost is significantly reduced compared to special vibration damping alloys such as silent alloys. The overall cost will be further reduced.

Furthermore, in this embodiment, since the small ball 11 is sealed by the plug 12, the screwing amount of the plug 12 is adjusted to prevent the small ball 11 from being sealed.
By changing the packing density of the tool body 1, the vibration characteristics of the tool body 1 can be varied in various ways. Therefore, this implementation P
By using JI, it is possible to easily cope with changes in the frequency of chatter vibrations that vary depending on cutting conditions and the like. However, this vibration characteristic can naturally be changed by changing the number, size, etc. of the small balls 11, in addition to adjusting the screwing amount of the plug I2.

In addition, in this embodiment, the indexable boring bar in which the tip 7 is attached to the tip of the tool body l has been described, but the present invention is not limited to this.
Of course, the present invention can also be applied to a boring bar that is integrated with the shank 4.

Further, in this embodiment, the cavity 10 is formed in the shape of a single elongated hole with a circular cross section, but the present invention is not limited to this, and may be modified to have a polygonal cross section. Yes, and the number is not limited to one.

Furthermore, the position of the cavity IO does not need to be coaxial with the tool body 1, but rather, as shown in FIG. It is preferable to provide it eccentrically on the other side tb of the tool body 1, which faces 1a across the tool axis PO. This means that the force applied to the tool body l during cutting is the tip 7
The direction of the principal component force acting on is greatest, and the tensile stress is greatest at the upper and lower ends of the tool body 1 (left and right ends in Fig. 4),
Alternatively, since bending stress is generated, by providing the cavity portion IO avoiding this portion, deterioration in tool rigidity due to a decrease in the wall thickness of the tool body 1 can be minimized.

In addition, in this embodiment, by enclosing the small spheres 11 with the plug 12, the plug 12 itself changes the packing density of the small spheres 11, but the present invention is not limited to this, and the plug 12 is A screw member for adjusting the filling density may be provided separately.

E. Effects of the Invention As explained above, the present invention reduces chatter vibrations that occur in the tool body due to friction between the small balls filled in the cavity of the tool body or between the small balls and the inner wall of the cavity. Because energy is absorbed, the vibration damping rate of the entire tool is improved compared to conventional boring bars made of cemented carbide, etc., which suppresses chatter vibration during cutting and dramatically improves machining accuracy. can be improved. Moreover, since its structure is simple, consisting of just small balls filled in the cavity of the tool body, it is extremely easy to manufacture and does not cause an increase in manufacturing costs.

In addition, when closing the opening of the cavity with a screw member,
Since the vibration characteristics can be changed by adjusting the screwing amount of the screw member, the optimum vibration characteristics can be obtained according to changes in cutting conditions.

By setting the ratio of the cross-sectional area of the cavity to the cross-sectional area of the tool body within the above-mentioned specific range, occurrence of chatter vibration can be effectively suppressed while avoiding deterioration of tool rigidity.

Furthermore, by eccentrically positioning the cavity in a specific direction with respect to the tool axis, it is possible to minimize the deterioration of tool rigidity due to a decrease in the wall thickness of the tool body.

[Brief explanation of drawings]

1 to 3 are views showing one embodiment of the present invention, in which FIG. 1 is a plan view, FIG. 2 is a view taken from one direction in FIG. 1, and FIG. 3 is a view in FIG. 1. A sectional view taken along the line ①-■, and FIG. 4 is a sectional view showing an example in which the cavity is eccentric with respect to the tool axis. 1... Tool body, 8... Cutting blade, 10 - Cavity, II... Small ball, I2... Plug (screw member).

Claims (1)

[Scope of Claims] (1) A boring bar in which a cutting edge is provided on the outer periphery of the tip of a tool body, in which a cavity opening to the outer surface of the tool body is formed inside the tool body; A boring bar characterized by having a cavity filled with granular material. (2) The boring bar according to claim 1, wherein the opening of the cavity to the outer surface of the tool body is closed with a screw member. (3) The ratio of the cross-sectional area A1 of the cavity in the cross section perpendicular to the axis of the tool body to the cross-sectional area A2 of the tool body including this cavity is set within the range shown by the following formula. The boring bar according to claim 1 or claim 2. 0.06≦A1/A2≦0.36 (4) In the front view of the tool body, the cavity portion is
Claims 1 and 2 are characterized in that the cutting edge is provided eccentrically toward one side of the tool body and the other side of the tool body that faces across the tool axis. Or the boring bar according to claim 3.