EP0320881A2
Expired / Lapsed
EP
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Twist drill
Assignee: Mitsubishi Materials Corp
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Filing: 1988-12-13
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Granted: —
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Expires: 2008-12-13
Abstract
Abstract A twist drill includes a cylindrical body (10) having an axis (O) of rotation therethrough and having a forward end which contacts a workpiece. The body (10) has a spiral flute (11) formed in an outer peripheral surface thereof so as to extend spirally along a length thereof to the forward end and a land (10a) disposed adjacent to the flute (11). The flute (11) has a first wall facing in the direction of rotation of the body (10) and a second wall extending from an inner end of the first wall to the outer periphery of the body (10). The first wall terminates at the forward end in a first cutting lip (12) having a radially outermost end disposed on the outer periphery of the body (10). The second wall is concavely shaped when viewed from the forward end and formed so that, assuming a first line (L) extending from the outermost end (Q) perpendicular to a second line (N) which connects the outermost end (Q) and the axis (O) of the body (10) the maximum distance between the first line and the second wall is set to range between 0.45D and 0.65D, wherein D is a diameter of the body (10).
Inventors
- 👤 Koujiro Mitsubishi Kinzoku K.K. Imanaga
- 👤 Shinichi Mitsubishi Kinzoku K.K. Nakamura
- 👤 Hideji Mitsubishi Kinzoku K.K. Hosono
- 👤 Yoshiyuki Mitsubishi Kinzoku K.K. Yanase
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-23 05:14
CPC Classifications
B; B23; B23B; B23B51/00; B23B51/02; B23B2251/00; B23B2251/18; B23B2251/24; B23B2251/241; B23B2251/40; B23B2251/406; Y; Y10; Y10T; Y10T408/00; Y10T408/78; Y10T408/89; Y10T408/909; Y10T408/9095; Y10T408/9097
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
213 words
1 A twist drill comprising a cylindrical body (10) having an axis (O) of rotation therethrough and having a forward end which contacts a workpiece, said body (10) having a spiral flute (11) formed in an outer peripheral surface thereof so as to extend spirally along a length thereof to said forward end and a land (10a) disposed adjacent to said flute (11), said flute (11) having a first wall facing in the direction of rotation of said body (10) and a second wall extending from an inner end of said first wall to the outer periphery of said body (10), said first wall terminating at said forward end in a first cutting lip (12) having a radially outermost end (Q) disposed on the outer periphery of said body (10), said second wall being concavely shaped when viewed from said forward end, characterized in that, assuming a first line (L) extending from said outermost end (Q) perpendicular to a second line (N) which connects said outermost end (Q) and said axis (0) of said body (10), said second wall is formed so that the maximum distance (W) between said first line (L) and said second wall is set to range between 0.45D and 0.65D, wherein D is a diameter of said body (10).
Claim 2
Dependent Claim
213 words
1 A twist drill comprising a cylindrical body (10) having an axis (O) of rotation therethrough and having a forward end which contacts a workpiece, said body (10) having a spiral flute (11) formed in an outer peripheral surface thereof so as to extend spirally along a length thereof to said forward end and a land (10a) disposed adjacent to said flute (11), said flute (11) having a first wall facing in the direction of rotation of said body (10) and a second wall extending from an inner end of said first wall to the outer periphery of said body (10), said first wall terminating at said forward end in a first cutting lip (12) having a radially outermost end (Q) disposed on the outer periphery of said body (10), said second wall being concavely shaped when viewed from said forward end, characterized in that, assuming a first line (L) extending from said outermost end (Q) perpendicular to a second line (N) which connects said outermost end (Q) and said axis (0) of said body (10), said second wall is formed so that the maximum distance (W) between said first line (L) and said second wall is set to range between 0.45D and 0.65D, wherein D is a diameter of said body (10).
Claim 3
Dependent Claim
37 words
A twist drill according to claim 1, in which said body (10) is made of a material selected from the group consisting of cemented carbide and cermet, and has a web thickness (T) of 0.2D to 0.35D.
Claim 4
Dependent Claim
66 words
A twist drill according to claim 1, in which said body (10) is made of a material selected from the group consisting of high speed steel and sintered metal high speed steel, said body (10) having a web thickness (T) of 0.15D to 0.3D, at least said forward end of said body (10) being coated with a hard coating which is harder than said body (10).
Claim 5
Dependent Claim
21 words
A twist drill according to claim 2, in which said body (10) has a flute-width ratio (A/B) of 0.5 to 0.9.
Claim 6
Dependent Claim
20 words
A twist drill according to claim 3, in which said body has a flute-width ratio (A/B) of 0.4 to 0.9.
Claim 7
Dependent Claim
80 words
A twist drill according to claim 2, in which the ratio of arc length (A₁) of said flute (11) to arc length (B₁) of said land (10a) at a cross-section taken perpendicular to the axis (O) of said body (10) is 0.9 to 1.2, and that portion of the walls of said flute (11) which contacts an imaginary cylinder inscribing a web portion of the drill being arcuately shaped at a radius of curvature (R) of between 0.15D and 0.2D.
Claim 8
Dependent Claim
79 words
A twist drill according to claim 3, in which the ratio of arc length (A₁) of said flute to arc length (B₁) of said land (10a) at a cross-section taken perpendicular to the axis (O) of said body (10) is 0.9 to 1.2, and that portion of the walls of said flute (11) which contacts an imaginary cylinder inscribing a web portion of the drill being arcuately shaped at a radius of curvature (R) of between 0.15D and 0.2D.
Claim 9
Dependent Claim
63 words
A twist drill according to claim 4, claim 5, claim 6 or claim 7, in which a web portion of the drill is ground off to provide a second cutting lip (13a) extending away from the axis (O) of said body (10), each of first and second cutting lips (12 and 13a) being formed to be linear as viewed from said forward end.
Claim 10
Dependent Claim
29 words
A twist drill according to claim 8, in which said first cutting lip (12) has a radial rake angle (δ) of -10° to -20° at said outermost end (Q).
Claim 11
Dependent Claim
83 words
A twist drill according to claim 9, in which, when a point P is defined by the intersection of a line tangential to said first cutting lip (12) with a line tangential to said second cutting lip (13a), the ratio of a distance (L₁) between said axis (O) of said body (10) and said point P to a distance (L₂) between said outermost end (Q) of said first cutting lip (12) and said point P is set to range between 0.4:1 and 0.7:1.
Claim 12
Dependent Claim
106 words
A twist drill according to claim 10, in which said forward end includes a first planar relief surface (18) provided with a relief angle (β₁) of 7° to 15° and extending along said first cutting lip (12), and a second planar relief surface (19) provided with a relief angle (β₂) greater than that of said first relief surface (18) so as to range from 15° to 25° and extending along said first relief surface (18), the intersection of said first relief surface (18) with said second relief surface (19) being parallel to said first cutting lip (12) and intersecting said axis (O) of said body (10).
Claim 13
Dependent Claim
28 words
A twist drill according to claim 11, in which the axial rake angle (ϑ) for said second cutting lip (13a) is set to be between 0° and -5°.
Claim 14
Dependent Claim
37 words
A twist drill according to claim 12, in which the angle (λ) defined between a ground surface (15) formed by the grinding and a rake surface (16) along said second cutting lip (13a) is 95° to 115°.
Claim 15
Dependent Claim
51 words
A twist drill according to claim 13, in which the angle (φ) defined by said axis (O) of said body (10) and a valley line (17) formed between said ground surface (15) and said rake surface (16) along said second cutting lip (13a) is set to be between 30° and 40°.
Claim 16
Dependent Claim
42 words
A twist drill according to claim 14, in which the axial distance ( l ) between said outermost end (Q) of said cutting lip (12) and a forward end (H) of a heel (11b) is set to be between 0.3D and 1.0D.
Claim 17
Dependent Claim
25 words
A twist drill according to claim 15, further comprising an oil passageway (22) formed in said body (10) and extending spirally along said flute (11).
Claim 18
Dependent Claim
34 words
A twist drill according to claim 16, in which the intersection of the walls of said flute (11) and the land (10a) of said body (10) is honed to provide a honed face (21).
Claim 19
Dependent Claim
17 words
A twist drill according to claim 17, in which said honed face (21) is a chamfered face.
Claim 20
Dependent Claim
17 words
A twist drill according to claim 17, in which said honed face (21) is a rounded face.
Claim 21
Dependent Claim
52 words
A twist drill according to claim 2, in which a second cutting lip (13a) formed by web thinning is inclined at an angle of 20° to 40° with respect to the line extending from the axis (O) of said body (10) to said outermost end (Q) of said first cutting lip (12).
Claim 22
Dependent Claim
55 words
A twist drill according to claim 3, in which a second cutting lip (1 3a) formed by web thinning is inclined at an angle (α) of 15° to 35° with respect to the line (N) extending from the axis (O) of said body (10) to said outermost end (Q) of said first cutting lip (12).
Claim 23
Dependent Claim
100 words
A twist drill according to claim 20, in which a pair of said first cutting lips (12) and a pair of said second cutting lips (13a) are provided and honed, and in which, assuming a first imaginary line extending from an inner ridgeline of one of said honed second cutting lips (13a) and a second imaginary line extending from an inner ridgeline of the other honed second cutting lip (13a), an intervening distance (C) between said first and second imaginary lines is set to range between 0.0 to 0.3mm, said honed second cutting lips defining a chisel edge (20) therebetween.
Claim 24
Dependent Claim
95 words
A twist drill according to claim 21, in which a pair of said first cutting lips (12) and a pair of said second cutting lips (13a) are provided, and in which, assuming a first imaginary line extending from an inner ridgeline of one of said second cutting lips (13a) and a second imaginary line extending from an inner ridgeline of the other second cutting lip (13a), an intervening distance (C) between said first and second imaginary lines is set to range between 0.0 to 0.3mm, said second cutting lips defining a chisel edge (20) therebetween.
Claim 25
Dependent Claim
25 words
An twist drill according to claim 22 or claim 23, in which said chisel edge (20) has a width (G) of between 0.0 and 0.4mm.
Claim 26
Dependent Claim
37 words
A twist drill according to claim 8, in which that corner at which said first cutting lip (12) and said second cutting lip (13a) meet forms a generally arcuately shaped edge when viewed from said forward end.
Claim 27
Dependent Claim
24 words
A twist drill according to claim 25, in which the radius of curvature (r) of said arcuately shaped edge is between 0.05D and 0.15D.
Claim 28
Dependent Claim
24 words
A twist drill according to claim 2, in which at least said forward end of said body (10) is coated with a hard coating.
Claim 29
Dependent Claim
33 words
A twist drill according to claim 3 or claim 27, in which said hard coating is composed of at least one material selected from the group consisting of TiN, TiC, TiCN and Al₂O₃.
Claim 30
Dependent Claim
24 words
A twist drill according to claim 8, in which that corner at which said first and second cutting lips meet forms a sharp edge.
References Cited (Backward Citations)
No citation records indexed.
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