Title of Invention

TWIST DRILL

Abstract

A twist drill (1), in particular for machining wrought aluminium alloys, has a drill shaft (2) and a cutting part (3) that extends to a drill point (6), spiral chucking grooves (4) extending along the cutting part (3), forming a drill core (15), the thickness (Dk) of the core at the drill point (6) being equal to (15 +/- 3) % of the drill diameter (D), the drill diameter (D) and/or core thickness (Dk) diminishing from the drill point (6) to the shaft (2), the twist drill having a primary clearance angle ( alpha 1) equal to (19 +/- 3) DEG and a secondary clearance angle ( alpha 2) equal to (26 +/- 4) DEG .

Full Text

Description Twist drill The invention relates to a twist drill, in particular for machining wrought aluminum alloys, with a drill shaft and a cutting part that extends to a drill tip, along which spiral chip flutes are provided, forming a drill core. In the machining of wrought aluminum alloys, e.g. AIMgSI or AIMgSi0.5, the use of conventional tools or twist drills can lead to a significantly restricted useful life of the tool, for example if the drill becomes jammed or stuck in the boring. Even the use of oils or lubricants that contain oils does not produce a satisfactory result, in addition to the fact that the use of such lubricants to extend the useful life of the tool is not always possible when the tools are used in the construction of automobile body parts. The reason is that the body work must be as clean as possible for subsequent welding and/or painting work as well as adhesive work, and a cleaning process prior to the further processing of the body parts is not always possible for cost and space reasons. The object of the invention is to create a twist drill of the type described above that can also be used for the machining of wrought aluminum alloys. The purpose of the invention is to make it possible to remove metal from this material in a series process at a boring depth which is in particular approximately 5 times the diameter of the boring tool. The invention teaches that this object can be accomplished by the features disclosed in Claim 1. Alternatively, the invention teaches that this object can be accomplished by the features disclosed in Claim 2. For this purpose the twist drill, at the drill tip, has a core thickness of (15 ± 3)% of the drill diameter and a tapering of the drill diameter or cutting diameter and/or of the chore thickness of the drill tip toward the shaft, as well as a primary clearance angle of (19 ± 3)° and a secondary clearance angle of (26 ± 4)°. The tapering of the core thickness or of the drill or cutting diameter of the twist drill is 0.5 mm to 0.9 mm, preferably 0.8 mm, with reference to a 100 mm drill length. A particularly preferred primary clearance angle is 18°, while a preferred secondary clearance angle is 25°. The tip angle of the twist drill is advantageously 120°. According to ISO Standard 5419, the primary or lateral clearance angle is the angle between a flank and a plane which contains the cutting edge and the hypothetical direction of the cutting movement at a selected point on the cutting edge, measured in the plane perpendicular to the radius at the selected point. This angle is measured at the face edge. The secondary or standard or normal clearance angle is the angle between a primary flank and a plane which contains the cutting edge and the hypothetical direction of the cutting direction at the selected point on the cutting edge, measured in the plane perpendicular to the cutting edge at the selected point. In one advantageous configuration, the twist drill advantageously has two internal cooling borings which emerge in the vicinity of the drill tip in the primary clearance faces. The spiral or twist angle of the chip flutes is approximately 30°. With this geometry, which is particularly suitable for drill diameters greater than 6 mm, two internal cooling borings are advantageously provided. With a likewise advantageous spiral or twist angle of approximately 40°, there are advantageously no internal cooling borings. This geometry is particularly suitable for twist drills with a drill diameter of less than or equal to 6 mm. In one particularly preferred configuration, the surfaces of the cutting part of the twist drill are initially ground to an average roughness of RA ≡ 0.2. Then the corresponding surfaces are precision ground to an average roughness of RA ≤0.1. The precision grinding is preferably executed both in the chip flutes as well as on the primary and secondary clearance faces and the circular lands of the cutting part. The above mentioned surfaces, i.e. the chip flutes, the clearance faces and/or the circular lands of the twist drill are advantageously coated, whereby preferably a diamond-like carbon coating (DLC or Balinit® Triton coating manufactured by Balzers) is provided. In an additional advantageous configuration, the land width of the cutting land measured in the vicinity of the drill tip is 50%, but preferably less than 50% of the drill diameter. The advantages achieved with the invention consist in particular of the fact that with a twist drill having the geometry described above and a coating of the above mentioned drill surfaces, it becomes possible to cut wrought aluminum alloys in a series process at a drilling depth of at least 5 times the drill diameter without the drill become stuck or jammed. The wear on the drill is thereby significantly reduced and a long useful life is achieved. A particularly short machining time can also be achieved by an increase in the cutting value. One exemplary embodiment of the invention is explained in greater detail below and illustrated in the accompanying drawing, in which: Figure 1 is a side view of a twist drill as claimed by the invention, Figure 2 is a side view of the drill tip and, on a larger scale, a selected point on a cutting edge to show the clearance angle, and Figure 3 is a schematic side view of the twist drill illustrated in Figure 1 with tapering drill diameter and drill core. Parts that correspond to one another in all the figures are identified by the same reference numbers. Figure 1 shows a twist drill 1 with an essentially cylindrical base body which has a shaft 2 and a cutting part 3 with a cutting part length I. In the cylindrical surface of the drill 1 or its cutting part 3, there are two chip flutes 4 that are diametrically opposite each other. The chip flutes 4 extend in a spiral fashion around the center axis 5 of the drill 1 and emerge in the end surface of the drill 1 which forms the drill tip 6. The center longitudinal axis 5 of the drill 1 is simultaneously its axis of rotation, around which the drill 1 can be rotated during its use. The twist drill 1 also has two primary clearance faces 7 and two primary cutting faces 8, as well as two secondary clearance faces 9, each of which has a circular land 10 and a secondary cutting face 11. The spiral or twist angle β is preferably (30 ± 3)°, advantageously 30°, or (40 ± 3)°, advantageously 40°. The tip angle y is preferably (120 ± 1)°. The end view in Figure 2 shows the internal cooling channel borings 12 for a lubricant that emerges in the primary clearance faces 7. During the machining of wrought aluminum alloys for a pulse-controlled minimum lubrication, the lubricant is transported via the cooling channel borings 12 and sprayed as a lubricant mist with a high proportion of air on the drilling surface to be cut. The chip flutes 4 and advantageously also the clearance faces 7 and the circular lands 10 are polished, i.e. precision ground with an average roughness RA ≤0.1. The surfaces of the cutting part 3 are thereby initially ground to an average roughness of RA ≡0.2 with a corresponding abrasive grain, e.g. D46. In a subsequent precision grinding step with a corresponding grain, e.g. D20, an average roughness of RA ≤ 0.1 is achieved. The chip flutes 4 and the clearance faces 7, 9 and the circular lands 10 are also provided with a coating, advantageously a DLC coating. The indicated core diameter Dk of the twist drill 1 is preferably 14% of the drill diameter D, measured at the drill tip 6. The clearance angles a1, a2 are shown in the enlarged detail illustrated in Figure 2, which shows a primary cutting edge 13. The primary or lateral clearance angle (primary clearance angle) a1 is thereby preferably 18°, while the secondary or standard clearance angle (secondary clearance angle) a2 is preferably 25°. In one advantageous configuration, the land width B of the cutting land 16 measured on the opposite, descending sides, i.e. on a center line 15 between the cutting edges, is preferably less than 50% of the drill diameter D (B As illustrated in Figure 1, the drill diameter D of the twist drill 1 tapers, beginning from the drill tip 6 to a drill diameter D' toward the shaft 2, so that D' is smaller than D (D' ≤ D). The preferably continuous tapering of the drill diameter D of the drill 1, beginning from the drill tip 6 or from the center line between the cutting edges 15 is approximately 0.8 mm, with reference to a 100 mm drill length. As shown in Figure 3, additionally or alternatively, the core diameter or the core thickness Dk of the drill core 14 preferably tapers continuously toward the shaft 2. The tapering of the core diameter Dk of the drill 1, beginning from the drill tip or from the center line between the cutting edges 15 is also approximately 0.8 mm with reference to a 100 mm drill length. Claims 1. Twist drill (1), in particular for the machining of wrought aluminum alloys, with a drill shaft (2) and a cutting part (3) that extends to a drill tip (6), - with spiral chip flutes (4) along the cutting part (3) that form a drill core (15), - with a core thickness (Dk) at the drill tip (6) of (15 ± 3)% of the drill diameter (D), - with a tapering of the core thickness (Dk) from the drill tip (6) toward the shaft (2), and - with a primary clearance angle (α1 of α1 = (19 ± 3)° and a secondary clearance angle (α2) of α2 = (26 ± 4)°. 2. Twist drill (1), in particular for the machining of wrought aluminum alloys, with a drill shaft (2) and a cutting part (3) that extends to a drill tip (6), - with spiral chip flutes (4) along the cutting part (3) that form a drill core (15), - with a core thickness (Dk) at the drill tip (6) of (15 ± 3)% of the drill diameter (D), - with a tapering of the drill diameter (D) from the drill tip (6) toward the shaft (2), and - with a primary clearance angle (α1) ofα1 = (19 ± 3)° and a secondary clearance angle (α2) of α2 = (26 ± 4)°. 3. Twist drill as claimed in Claim 1 or 2, characterized by a twist angle (B) of (J = (30 ± 3)°, preferably ft = 30°, or ft = (40 ± 3)°, preferably ft = 40°. 4. Twist drill as claimed in one of the Claims 1 to 3, characterized by at least one lubricant boring (12) that emerges in the vicinity of the drill tip (6). 5. Twist drill as claimed in one of the Claims 1 to 4, characterized by a tapering of the core thickness (Dk) and/or of the drill diameter (D) by (0.7 ± 0.2) with reference to a drill length (I) of 100 mm. 6. Twist drill as claimed in one of the Claims 1 to 5, characterized by precision-ground surfaces of the cutting part (3), in particular of the chip flutes (4), of the clearance faces (7) and/or of the circular lands (10). 7. Twist drill as claimed in Claim 6, characterized by an average roughness of RA ≤ 0.1. 8. Twist drill as claimed in one of the Claims 1 to 7, characterized by a coating, preferably a DLC coating of the chip flutes (4), of the clearance faces (7, 9) and/or of the circular lands (10). 9. Twist drill as claimed in one of the Claims 1 to 8, characterized by a primary clearance angle of α1 = (18 ± 0.5)°. 10. Twist drill as claimed in one of the Claims 1 to 9, characterized by a secondary clearance angle of α2 = (25 ± 0.5)° 11. Twist drill as claimed in one of the Claims 1 to 10, characterized by a tip angle (y) of y = (120 ± 5)°, preferably y = (120 ± 0.5)°. 12. Twist drill as claimed in one of the Claims 1 to 11, characterized by a land width (B) of the cutting land (16) of less than or equal to 50% of the drill diameter (D).

Documents:

3344-chenp-2006 correspondence others 18-07-2011.pdf

3344-CHENP-2006 FORM-13 18-07-2011.pdf

3344-chenp-2006 power of attorney 18-07-2011.pdf

3344-CHENP-2006 CORRESPONDENCE OTHERS 23-06-2011.pdf

3344-CHENP-2006 AMENDED CLAIMS 09-04-2012.pdf

3344-CHENP-2006 AMENDED PAGES OF SPECIFICATION 09-04-2012.pdf

3344-CHENP-2006 CORRESPONDENCE PO.pdf

3344-CHENP-2006 EXAMINATION REPORT REPLY RECEIVED 09-04-2012.pdf

3344-CHENP-2006 FORM-1 09-04-2012.pdf

3344-CHENP-2006 FORM-18.pdf

3344-CHENP-2006 FORM-3 09-04-2012.pdf

3344-CHENP-2006 FORM-5 09-04-2012.pdf

3344-CHENP-2006 OTHER PATENT DOCUMENT 09-04-2012.pdf

3344-CHENP-2006 POWER OF ATTORNEY 09-04-2012.pdf

3344-CHENP-2006 CORRESPONDENCE OTHERS.pdf

3344-CHENP-2006 CORRESPONDENCE PO.pdf

3344-CHENP-2006 FORM 18.pdf

3344-chenp-2006-abstract.pdf

3344-chenp-2006-claims.pdf

3344-chenp-2006-correspondnece-others.pdf

3344-chenp-2006-description(complete).pdf

3344-chenp-2006-drawings.pdf

3344-chenp-2006-form 1.pdf

3344-chenp-2006-form 26.pdf

3344-chenp-2006-form 3.pdf

3344-chenp-2006-form 5.pdf

3344-chenp-2006-pct.pdf