GB2327055A

GB2327055A - Tool holder

Info

Publication number: GB2327055A
Application number: GB9804040A
Authority: GB
Inventors: Masahiro Taguchi; Yusaku Yamamoto; Hirohide Kugimiya
Original assignee: Nikken Kosakusho Works Ltd
Current assignee: Nikken Kosakusho Works Ltd
Priority date: 1997-07-07
Filing date: 1998-02-26
Publication date: 1999-01-13
Anticipated expiration: 2018-02-26
Also published as: FR2765509A1; FR2765509B1; GB9804040D0; IT1298089B1; GB2327055B; JPH1128633A; JP3701440B2; ITMI980011A1

Abstract

A tool holder has a pair of drive-key grooves 122,123 having different depths and a notch groove 124 formed in the vicinity of the shallow drive-key groove 121. A cutaway portion 14 is formed in the bottom surface of the V-shaped groove 121 to a predetermined depth on the side opposite the notch groove 124 with respect to a diametric line that passes through the centre of the shallow drive-key groove 122. The cutaway portion 14 is formed over a predetermined angle range starting from a position that is separated from the diametric line by a predetermined angle such that the mass balance of the flange in the circumferential direction is secured.

Description

TOOL HOLDER The present invention relates to a tool holder used for attaching a tool to a spindle of a machine tool, and more particularly to a tool holder that can ensure rotational balance during high speed rotation.

A conventional tool holder will be described with reference to FIGS. 3 and 4. FIG. 3 is side view of a tool holder that conforms to the ISO standard, and FIG. 4 is a plan view of the tool holder as viewed in the direction of arrow B in FIG. 3.

In FIGS. 3 and 4, the tool holder 30 has a tapered shank portion 31 to be inserted into a spindle of an unillustrated machine tool, a gripping flange 32 formed at the larger diameter end of the tapered shank portion 31, and a tubular tool attachment portion 33 that extends from one end surface of the flange 32 that is opposite the tapered shank portion 31. The tool attachment portion 33 extends in the direction away from the tapered shank portion 31 such that the axis of the tool attachment portion 33 coincides with the axis of the tapered shank portion 31.

On the outer circumference of the gripping flange 32 is formed a groove 321, for example a V-shaped groove, of a predetermined depth. During a tool change operation, gripping fingers of a tool changing apparatus come into engagement with the groove 321. Also, a pair of generally longitudinal substantially diametrically opposed drive-key grooves or keyways 322 and 323 are respectively formed in the flange 32. The keyway 322 has a radial depth smaller than the radial depth of the keyway 323. Moreover, in the vicinity of the keyway 322, a generally longitudinal Vshaped notch or groove 324 is formed in the flange 32. The notch or groove 324 is used to maintain a predetermined rotational phase of a tool held by the tool holder when the tool is inserted into a tool pot of a tool magazine together with the tool holder.

In such a conventional tool holder, since the keyway 322 and 323 formed in the flange 32 have different depths and the notch 324 is formed in the vicinity of the keyway 322, the flange 32 has an asymmetrical shape with respect to the axis thereof, causing mass imbalance.

Therefore, when such a tool holder is rotated at high speed (equal to or greater than 10000 rpm) during precision finishing, rotational imbalance occurs in the flange because of the effect of eccentric force generated during high speed rotation, with the result that the tool holder including the tool causes low amplitude vibration, which is a cause of generation of chatter.

The present invention has been accomplished to at least partially solve the above-mentioned problems, and the invention seeks to provide a tool holder which facilitates adjustment of rotational imbalance of the flange without violating the ISO standard.

According to the present invention, there is provided a tool holder comprising a shank portion for cooperation with a machine tool; a gripping flange formed at one end of said shank portion; a tool attachment portion which extends from the end surface of said flange which is opposite said shank portion, said tool attachment portion extending in the direction away from said shank portion in alignment with the axis of said shank portion; a groove formed in the outer circumference of said flange and having a predetermined depth; a pair of substantially diametrically opposed keyways formed in said flange, said keyways having different radial depths; and a notch formed in said flange in the vicinity of the shallower of said keyways, wherein a cutaway portion for reducing rotational imbalance of said flange is formed radially inwardly at a portion of said groove to a predetermined depth and over a predetermined angle range on the side of the flange opposite said notch with respect to a diametric line which passes through the center of said shallow keyway.

Preferably, the depth and angle range of the cutaway portion are determined in accordance with the radius of the flange.

Preferably, the cutaway portion is machined through use of an end mill.

In the present invention, the mass balance of the flange in the circumferential direction is attained through formation of a cutaway portion in the bottom surface of the groove to a predetermined depth and over a predetermined angle range on the side opposite the notch with respect to a diametric line that passes through the centre of the shallow keyway.

Therefore, rotational imbalance of the flange is eliminated, which imbalance is generated because of difference in depth between the pair of keyways and formation of the notch. Accordingly, it is possible to provide a tool holder that does not cause chatter even during high speed rotation.

Also, in the present invention, since the cutaway portion for eliminating rotational imbalance is formed in the bottom surface of the groove of the flange, the rotational imbalance can readily be substantially eliminated without violating the ISO standard.

Various other objects, features and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description of the preferred embodiment when considered in connection with the accompanying drawings, in which: FIG.1 is a side view of a tool holder according to an embodiment of the present invention; FIG. 2 is a sectional view taken along line A-A in FIG. 1; FIG. 3 is a side view of a conventional tool holder; and FIG. 4 is plan view of the conventional tool holder as viewed in the direction of arrow B in FIG. 3.

An embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a side view of a tool holders according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line A-A in FIG. 1.

As shown in FIGS. 1 and 2, a tool holder 10 according to the present embodiment has a tapered shank portion 11 to be inserted into a spindle of an unillustrated machine tool, a gripping flange 12 formed at the larger-diameter end of the tapered shank portion 11, and a tool attachment portion 13, which is this case is tubular, that extends from the end surface of the flange 12 which is opposite the tapered shank portion 11. The tool attachment portion 13 extends in the direction away from the tapered shank portion 11 such that the axis of the tool attachment portion 13 coincides with the axis of the tapered shank portion 11.

On the outer circumference of the gripping flange 12 is formed a groove 121 of the predetermined depth. In the embodiment illustrated, the groove comprises a circumferential base region 124 and sloping walls 125, 126.

In other embodiments the groove may be generally V-shaped, U- shaped or any other configuration which the skilled person will understand to be suitable. During a tool change operation, gripping fingers of a tool changing apparatus come into engagement with the groove 121. Also, substantially diametrically opposed, generally longitudinal drive-key grooves or keyways 122 and 123 are respectively formed in the flange 12. The keyway 122 has a radial depth smaller than the radial depth of the keyway 123. Moreover, in the vicinity of the keyway 122, a generally longitudinal V-shaped notch or groove 124 is formed in the flange 12.

The notch or groove 124 is used to maintain a predetermined rotational phase of a tool held by the tool holder when the tool is inserted into a tool pot of a tool magazine together with the tool holder.

Moreover, a cutaway portion 14 for reducing or eliminating rotational imbalance of the flange 12 is formed in the base region of the groove 121 to a predetermined depth d on the side opposite the notch 124 with respect to a diametric line L that passes through the center of the shallow keyway 122. The cutaway portion 14 is formed over an angle range 82 starting from a position that is separated from the diametric line L by an angle 61.

The cutaway portion can be machined easily through use of an end mill or a like tool without violating the ISO standard.

For example, in the case of a tool holder according to standard number ISO 50 of the ISO standard, the diameter of the flange 12 is 97.50 mm. In order to adjust the rotational imbalance of the flange 12, the angle Ol was set to 230, the angle 82 was set to 400, and the depth was set to 4.8 mm. Through the formation of the cutaway, the rotational imbalance of the flange was eliminated.

Also, in the case of a tool holder according to standard number ISO 40 of the ISO standard, the diameter of the flange 12 is 63.55 mm. In order to adjust the rotational imbalance of the flange 12, the angle Ol was set to 240, the angle 02 was set to 600, and the depth was set to 3.5 mm.

Through the formation of the cutaway, the rotational imbalance of the flange was eliminated.

In the above-described embodiment, the mass balance of the flange in the circumferential direction is attained through formation of a cutaway portion 14 in the bottom surface of the groove 121 to a predetermined depth d on the side opposite the notch 124 with respect to a diametric line L that passes through the center of the shallow keyway 122, wherein the cutaway portion 14 is formed over a predetermined angle range 82 starting from the position separated from the diametric line L by an angle 81.

Therefore, rotational imbalance of the flange 12 is reduced or eliminated, which imbalance is generated because of difference in depth between the pair of keyways 122 and 123 and formation of the notch or groove 124. Accordingly, it is possible to provide a tool holder that does not cause chatter even during high speed rotation, thereby enabling precise workpiece machining.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.

In the present specification, unless the context requires otherwise, "longitudinal" refers to a direction generally parallel to axis of the shank portion, and "longitudinally" should be interpreted accordingly; "radial" refers to a direction radial to a line which includes the axis of the shank portion and "radially" should be interpreted accordingly; "circumference" refers to an arc or a portion of an arc described on a surface by a point on a radius when said radius is rotated about a line which includes said axis of the shank portion and "circumferential" and "circumferentially" should be interpreted accordingly and "diametrically opposed" refers to the respective positions at which a diameter intersects a circumference.

Claims

CLAIMS:

1. A tool holder comprising a shank portion for cooperation with of a machine tool; a gripping flange formed at one end of the said shank portion; a tool attachment portion which extends from the end surface of the said flange which is opposite said shank portion, said tool attachment portion extending in the direction away from said shank portion in alignment with the axis of the said shank portion; a groove formed in the outer circumference of said flange and having a predetermined depth; a pair of substantially diametrically opposed keyways formed in said flange said keyways having different radial depths; and a notch formed in said flange in the vicinity of the shallower of said keyways, wherein a cutaway portion for reducing rotational imbalance of said flange is formed radially inwardly at a portion of said groove to a predetermined depth and over a predetermined angle range on the side of the flange opposite said notch with respect to a diametric line which passes through the center of the said shallow keyway.

2. A tool holder according to Claim 1, wherein the depth and angle range of said cutaway portion are determined in accordance with the radius of said flange.

3. A tool holder according to Claim 1 or 2, wherein the cutaway portion is machined through use of an end mill.

4. A tool holder according to any preceding claim wherein the groove comprises a circumferential base portion and opposed walls sloping with respect to the radial direction of the flange and extending respectively from said base portion.

5. A tool holder substantially as hereinbefore'described with reference to, or as illustrated in, Figures 1 and 2.