US4065224A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Twist drills
Assignee: Osborn Mushet Tools Ltd
•
Filing: 1976-10-07
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Granted: 1977-12-27
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Expires: 1996-10-07
Abstract
Abstract A twist drill the cross-sectional shape of which is such that, although it can be sharpened on a conventional machine so that its cutting edges are contained in the surface of an imaginary cone, its cutting edges are curved and their lip rake is substantially constant radially outwards of the drill core.
Inventors
- 👤 Keith Siddall
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 10:44
CPC Classifications
B; B23; B23B; B23B51/00; B23B51/02; B23B2251/00; B23B2251/04; B23B2251/043; B23B2251/24; B23B2251/241; B23B2251/40; B23B2251/406; Y; Y10; Y10T; Y10T408/00; Y10T408/89; Y10T408/909; Y10T408/9095; Y10T408/9097
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
103 words
A twist drill having a cross-sectional shape which is convex in the surfaces of the drill faces, the convexity being of such an extent that it conforms substantially to a radius of between 0.9 and 1.2 of the drill radius, the lip rake angle being substantially constant along the cutting edges radially outwards of the core portion of the drill, the helix angle being between 25° and 45°, and the point angle being between 90° and 150°, whereby the cutting edges are curved but contained in the surface of an imaginary cone so that the drill can be sharpened on a conventional machine.
Claim 2
Dependent Claim
103 words
A twist drill having a cross-sectional shape which is convex in the surfaces of the drill faces, the convexity being of such an extent that it conforms substantially to a radius of between 0.9 and 1.2 of the drill radius, the lip rake angle being substantially constant along the cutting edges radially outwards of the core portion of the drill, the helix angle being between 25° and 45°, and the point angle being between 90° and 150°, whereby the cutting edges are curved but contained in the surface of an imaginary cone so that the drill can be sharpened on a conventional machine.
Claim 3
Dependent Claim
21 words
A twist drill according to claim 1, intended primarily for drilling cast iron, the point angle being between 90° and 120°.
Claim 4
Dependent Claim
26 words
A twist drill according to claim 2, in which the helix angle is between 35° and 40° and the rake angle is between 5° and 15°.
Claim 5
Dependent Claim
44 words
A twist drill according to claim 1, intended primarily for the drilling of low and medium alloy carbon steel, the point angle being between 110° and 125°, the helix angle being between 30° and 40° and the rake angle being between 10° and 20°.
Claim 6
Dependent Claim
39 words
A twist drill according to claim 1, intended primarily for the drilling of aluminium, the point angle being between 100° and 130°, the helix angle being between 35° and 45°, and the rake angle being between 15° and 20°.
Claim 7
Dependent Claim
16 words
A twist drill according to claim 1 wherein the rake angle is between 10° and 20°.
References Cited (Backward Citations)
US262588A
Cited
US1309706A
Cited
US2328629A
Cited
US2778252A
Cited
US2966081A
Cited
US3443459A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-12-26 | 1981-06-27 | 1981-12-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-12-26 | 1985-06-27 | 1985-12-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-12-26 | 1989-06-27 | 1989-12-27 | $7700.00 | Window Closed / Lapsed |