Helically fluted twist drill device

[0002] The present application is a continuation-in-part of patent application U.S. Ser. No. 08/940,347 filed Sep. 30th 1997 now U.S. Pat. No. 6,045,305. All the subject matter of the aforementioned U.S. Ser. No. 08/940,347 is incorporated herein by reference.

[0003] 1. Field of the Invention

[0004] The present invention relates to a helically fluted twist drill device.

[0005] More specifically, the present invention relates to a helically fluted twist drill device for cutting materials.

[0006] 2. Information Disclosure Statement

[0007] Three-flute twist drills otherwise known as core drills are primarily used for enlarging and finishing drilled, cast or punched holes. Generally, such three-flute drills will not produce original holes.

[0008] Some three-flute drills are manufactured by means of a process which includes the step of providing a cylindrical blank which defines three equidistantly spaced longitudinally extending flutes and bores.

[0009] The cylindrical blank or rod is extruded when it is still in its soft state. The extruded material is then heat treated or sintered to bring such material to its final state of hardness.

[0010] Subsequently, a helical flute is machined between adjacent bores such that the resultant machined twist drill includes three flutes or channels which extend helically from a shank portion disposed adjacent to one end of the blank to a second end of the blank.

[0011] Next, the second end of the blank is machined to provide a point. The bores are provided so that a cutting fluid under pressure can be fed through the twist drill while the drill is rotating at high speed. The cutting fluid flows from the shank to the point so that lubrication of the twist drill within the drilled hole is accomplished. Also, the cutting fluid flows from the point of the twist drill back through the flutes. Such flow of the cutting fluid from the point through the flutes conveys the cut material from the point towards the shank of the twist drill. The aforementioned process is known as chip evacuation.

[0012] Accordingly, it is desirable that the cross sectional area of the flutes or channels be as large as possible so as to avoid clogging of the same by chips or material being drilled or cut during the drilling operation.

[0013] Nevertheless, when large flutes are machined, there is a tendency to cut the flute in such a way that the surface of the flute exposes the adjacent bore. If such exposure occurs, the resultant twist drill will be useless.

[0014] Also, in order to machine the flutes, various shape grinding wheels have been required. The multiplicity of grinding wheels of various shapes has often been necessary in order to generate the flute form needed for that particular drill size. The use of special grinding wheels can be very expensive with a single wheel costing between $300.00-$400.00. Also, 12-15 different wheels are required in order to make various drill sizes.

[0015] Additionally, the operation of truing the form of the grinding wheels as such wheels wear is labor intensive.

[0016] The present invention overcomes the aforementioned problems by providing an arrangement in which twist drills of various sizes can be machined using a single straight grinding wheel such as a type IAI grinding wheel with a {fraction (1/32)} inch-{fraction (1/16)} inch radius.

[0017] In the grinding operation according to the present invention, the axis of the grinding wheel is disposed at an approach angle within the range 2-4 degrees relative to the longitudinal axis of the twist drill.

[0018] Therefore it is a primary objective of the present invention to provide a fluted twist drill and a method of manufacturing the same which overcomes the problems associated with the prior art arrangements.

[0019] Another object of the present invention is the provision of a fluted twist drill having at least three flutes. Each flute defines a flute surface which when taken in a section normal to the longitudinal axis of the twist drill is of generally S-shaped configuration so that hooking the flutes is inhibited, that is the flutes have no undercut areas.

[0020] A further object of the present invention is the provision of a fluted twist drill having at least three flutes which can be manufactured in various sizes using a standard straight grinding wheel.

[0021] Other objects and advantages of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings.

[0022] The present invention relates to a helically fluted twist drill device for cutting materials. The device includes a cylindrical core having a first diameter, a longitudinal axis and a first and a second extremity, the second extremity defining a cutting point. At least three portions extend helically outwardly away from the core so that the portions define a second diameter. The arrangement is such that adjacent portions define therebetween a helical flute. Each of the flutes has a flute surface which is of S-shaped configuration when viewed as a cross section disposed normal to the longitudinal axis, the cross section being viewed in a direction from the first towards the second extremity. Each of the portions further defines a helical bore connected to a source of a cutting fluid for permitting a flow of the cutting fluid through the bore towards the cutting point. The arrangement is such that in use of the device, the cutting fluid conveys the materials away from the cutting point through each flute. The first diameter has a dimension within a first range which is 20-35% of a dimension of the second diameter. Also, the second extremity of the core and adjacent portions is of cusp-shaped configuration for defining the cutting point so that wandering of the drill device is inhibited.

[0023] Many modifications and variations of the present invention will be readily apparent to those skilled in the art by a careful consideration of the detailed description of the present invention described hereinafter taken in conjunction with the annexed drawings. However, such modifications and variations fall within the spirit and scope of the present invention as defined by the appended claims.

[0024] FIG. 1 is a side elevational view of a helically fluted twist drill according to the present invention;

[0025] FIG. 1A is a sectional view taken on the line 1A—1A of FIG. 1;

[0026] FIG. 1B is an enlarged view of FIG. 1A;

[0027] FIG. 1C is a side elevational view of a helically fluted twist drill according to a further embodiment of the present invention;

[0028] FIG. 1D is a side elevational view of a helically fluted twist drill according to yet another embodiment of the present invention;

[0029] FIG. 2 is an enlarged sectional view taken on the line 2—2 of FIG. 1D, but showing how the grinding of the drill is accomplished;

[0030] FIG. 3 is a side elevational view of a helically fluted twist drill according to an alternative embodiment of the present invention;

[0031] FIG. 4. is a cross sectional view of a conventional prior art two flute twist drill;

[0032] FIG. 5 is a cross sectional view of a parabolic prior art two flute twist drill;

[0033] FIG. 6 is a cross sectional view of a conventional prior art two flute twist drill showing a portion of the grinding wheel with an axis of rotation disposed normal to the longitudinal axis of the drill;

[0034] FIG. 7 is a side view taken on the line 7—7 of FIG. 6;

[0035] FIG. 8 is a side view of a parabolic three flute twist drill according to the present invention showing the angle of approach of the grinding wheel relative to the drill;

[0036] FIG. 9 is an enlarged view of the tip of the drill showing an alternative embodiment in which the corners are protected; and

[0037] FIG. 10 is an enlarged view of an alternative embodiment of the present invention which includes a separate point.

[0038] Similar reference characters refer to similar parts throughout the various views of the drawings.

[0039] FIG. 1 is a side elevational view of a helically fluted twist drill device generally designated 10 according to the present invention for cutting materials 12. The device includes a cylindrical core 20 having a first diameter D1, a longitudinal axis A and a first and a second extremity 22 and 24 respectively, the second extremity 24 defining a cutting point 26. At least three portions 28, 29 and 30 respectively extend helically outwardly away from the core 20 so that the portions 28-30 define a second diameter D2. FIG. 1A is a section taken on the line 1A—1A of FIG. 1.

[0040] FIG. 1A shows adjacent portions 28-29, 29-30 and 30-28 defining therebetween helical flutes 33, 34 and 35 respectively. Each of the flutes 33-35 has a flute surface 32 which is of S-shaped configuration when viewed as a cross section disposed normal to the longitudinal axis A, the cross section being viewed in a direction as indicated by the arrow 39 from the first extremity 22 towards the second extremity 24.

[0041] FIG. 1B is an enlarged view of FIG. 1A. FIG. 1B shows that each of the portions 28-30 further defines a helical bore 36, 37 and 38 connected to a source of a cutting fluid for permitting a flow of the cutting fluid through each bore 36-38 towards the cutting point 26. The arrangement is such that in use of the device 10, the cutting fluid conveys the materials 12 away from the cutting point 26 through each of the flutes 33-35 as shown in FIG. 1. The first diameter D1 has a dimension within a first range which is 20-35% of a dimension of the second diameter D2. Also, the second extremity 24 of the core 20 and adjacent portions 28-30 is of cusp-shaped configuration for defining the cutting point 26.

[0042] In a more specific embodiment of the present invention, each of the portions 28-30 extends helically around the core 20 between the first and the second extremities 22 and 24 respectively of the core 20. More particularly, each of the portions 28-30 extends helically around the core 20 from between the first and the second extremities 22 and 24 respectively of the core 20 to the second extremity 24 of the core 20.

[0043] Also, as shown in FIG. 1B, each of the portions 28-30 such as portion 28, in the vicinity of the second diameter D2, has a leading edge 41 and a heel clearance 43, the heel clearance 43 trailing behind the leading edge 41 in use of the drill device 10.

[0044] Furthermore, each of the portions 28-30 is helically disposed relative to the longitudinal axis A at a helix angle H within a range 25-35 degrees as shown in FIG. 1.

[0045] Additionally, each flute surface 32 is of sinusoidal configuration when viewed in a direction as indicated by the arrow 45 from the second extremity 24 towards the first extremity 22 of the core 20 for providing an increased flute cross-section for the passage therethrough of the materials 12 cut by the cutting point 26.

[0046] Moreover, each helical bore 34-36 extends from adjacent to the first extremity 22 of the core 20 to the second extremity 24 of the core 20.

[0047] Additionally, the cutting point 26 is formed by grinding the second extremity 24 of the core 20 with a grinding wheel and each bore 34-36 is disposed equidistantly from the longitudinal axis A as shown in FIG. 1B so that each bore 34-36 has a center C located on a diameter D having a dimension which is within a range 45-55% of a dimension of the second diameter D2.

[0048] In yet another embodiment of the present invention as shown in FIG. 1C, a drill device 100 includes a first member 102 which extends from the first extremity 122 of the core 120 to between the first extremity 122 and the second extremity 124 of the core 120 and a second member 104 is secured to the first member 102, the second member 104 extending coaxially from the first member 102 to the cutting point 126. Preferably, the second member 104 is a cermet and a fastener 106 removably fastens the second member 104 to the first member 102 such that when the cutting point 126 becomes worn, the second member 104 is able to be replaced.

[0049] FIG. 1D is a side elevational view a helically fluted twist drill device generally designated 10aaccording to another embodiment of the present invention. As shown in FIG. 1D, the helically fluted twist drill device 10ais designed for cutting materials 12aand particularly for finishing a bore Ba defined by a workpiece Wa. The twist drill device 10aincludes a shank 14ahaving a first and a second end 16aand 18arespectively. A cylindrical core 20ahas a first diameter D1aand a first and a second extremity 22aand 24arespectively. The core 20aextends coaxially relative to the shank 14aand from the second end 18aof the shank 14a.The second extremity 24aof the core 20adefines a point 26a.

[0050] FIG. 2 is an enlarged sectional view taken on the line 2—2 of FIG. 1D. FIG. 2 shows that at least three portions 28a,29aand 30arespectively extend helically outwardly away from the core 20aso that the portions 28a-30adefine a second diameter D2a.The arrangement is such that adjacent portions 28a-29a,29a-30aand 30a-28adefine therebetween a surface 32aof a helical flute 34a.Each of the portions 28a-30afurther define a helical bore 36a,37aand 38arespectively connected to a source Sa shown in FIG. 1D of a cutting fluid 40afor permitting a flow as indicated by the arrow 42aof the cutting fluid 40athrough the bore 36afrom the shank 14atowards the point 26a.

[0051] In use of the twist drill device 10a, the cutting fluid 40aconveys the cut materials 12afrom the vicinity of the point 26athrough each flute 34atowards the shank 14a.The first diameter D1ahas a dimension within a first range I which is 20-35% and preferably 25-30% of a dimension of the second diameter D2a.Also, the surface 32ais machined such that intersection of the portions 28a-30awith any normal extending outwardly from the surface 32ais inhibited.

[0052] In a more specific embodiment of the present invention the shank 14ais of cylindrical configuration.

[0053] Also, as shown in FIG. 1D, the first extremity 22aof the core 20aextends from the second end 18aof the shank 14a.

[0054] Additionally, as shown in FIG. 2 which is an enlarged sectional view taken on the line 2—2 of FIG. 1D, the surface 32ain cross section is of sinusoidal configuration.

[0055] More specifically, the surface 32ain cross section from a first location 46aon the second diameter D2adefines a rake angle Ra within a second range II which is 1.5-2.5 degrees and preferably 2 degrees from a radius of the second diameter D2apassing through the first location 46a.

[0056] More particularly, the rake angle Ra is such that during rotation of the device 10a,the surface 32aadjacent to the second diameter D2ais of scoop shaped configuration for assisting in cutting and conveying the materials 12ain a direction as indicated by the arrow 33afrom the point 26atowards the shank 14a.

[0057] Furthermore, the scoop shaped configuration of the surface 32ais deepest at a second location 48awhich is disposed between the first and second diameter D1aand D2arespectively. The second location 48ais disposed on a third diameter D3a,the third diameter D3abeing concentric with the first and second diameter D1aand D2arespectively. The third diameter D3ahas a dimension which is within a third range III which is 8-15% and preferably 10-13% less than a dimension of the second diameter D2a.

[0058] In a preferred embodiment of the present invention, the portions 28a-30aextend helically along the core 20a,with each portion 28a-30ahaving a helix angle Ha within a fourth range IV which is 25-35 degrees and preferably 30 degrees.

[0059] Each bore fore example bore 36ahas a center Ca located on a fourth diameter D4a.The fourth diameter D4awhich is concentric to the other diameters D1a-D3ahas a dimension within a fifth range V which is 45-55% and preferably 47-53% of the dimension of the second diameter D2a.More specifically, each center Ca is located on the fourth diameter D4aand the bore 36ahas a wall 50a.The arrangement is such that a first radius of the device 10aextending through the center Ca and a second radius tangent to the wall 50adefine therebetween an angle within a sixth range VI which is 8-12 degrees and preferably 10 degrees.

[0060] Adjacent surfaces of adjacent flutes define therebetween a land 52awhich extends along a portion of the second diameter D2a.Each of the lands 52ais within a seventh range VII which is 8-12 mm and preferably 10 mm.

[0061] The twist drill device 10adefines an angle of approach within an eighth range VIII which is 1-4 degrees and preferably 2-4 degrees.

[0062] In one embodiment of the present invention, the drill device 10ais machined to a combination of:

[0063] a first range I

[0064] a second range II

[0065] a third range III

[0066] a fourth range IV

[0067] a fifth range V

[0068] a sixth range VI

[0069] a seventh range VII

[0070] an eighth range VIII. The ranges I-VIII being as described hereinbefore.

[0071] In yet another embodiment of the present invention as shown in FIG. 3, the shank 14bis tapered. Also, as shown in FIG. 3, a tang 44bextends from the first end 16bof the shank 14b.

[0072] FIG. 4. is a cross sectional view of a conventional prior art two flute twist drill.

[0073] FIG. 5 is a cross sectional view of a parabolic prior art two flute twist drill.

[0074] FIG. 6 is a cross sectional view of a conventional prior art two flute twist drill showing a portion of the grinding wheel 54cwith axis of rotation Ar disposed normal to the longitudinal axis Ac of the drill 10c.

[0075] FIG. 7 is a side view taken on the line 7—7 of FIG. 6.

[0076] FIG. 8 is a side view of a parabolic three flute twist drill according to the present invention showing the angle of approach VIII of the grinding wheel 54arelative to the drill 10a.

[0077] The method according to the present invention includes grinding at least three helical flutes 32abetween adjacent portions 28a-30aby means of a standard three inch straight IAI wheel 54aas shown in FIG. 2.

[0078] More specifically, because the side walls 56aand 58aof the wheel 54aare parallel and because no normal Na extending outwardly from the surface 32aintersects any of the portions 28a-30a,grinding of the flutes can be accomplished regardless of the size of the drill device 10a.

[0079] FIG. 9 is an enlarged view of the tip of the drill showing an alternative embodiment in which the corners are protected. More specifically, as shown in FIG. 9, the tip or cutting point 26 of the drill defines an angle A of approximately 130 degrees. However, the corners 202 and 204 include corner chamfers or protected corners so that in the region of these chamfers, the cutting point of the drill defines an angle B of 90 degrees. The terms protected corners, corner chamfer, corner radius and double angle point as used in the subject application have the same basic meaning.

[0080] FIG. 10 is an enlarged view of an alternative embodiment of the present invention which includes a separate point or cutting point 26d.The cutting point 26dis manufactured from tungsten carbide or the like and includes one or more bores 34d,35dand 36dfor conveying cutting fluid. The point 26dis secured to the end of the body 102dso that a plenum 302 is in fluid communication with the bores 34d-36dso that fluid is conveyed through the body 102dto the point and through the bores 34d-36dalong the entire flight length 304.

[0081] The key features of the present invention include the provision of a twist drill having:

[0082] 1) Three parabolic flutes for faster penetration. (A two flute drill does not penetrate as fast as a three flute drill.)

[0083] 2) Through the tool coolant, for cooling, lubrication and chip evacuation.

[0084] Two of the biggest problems with drilling are the inability to eject chips fast enough and the problem of getting coolant to the point of the cut deep into the hole, which causes premature tool failure due to heat.

[0085] More specifically, in the drilling art the term “parabolic flute form” as used herebefore is used to describe a flute the surface of which when taken in a section normal to the longitudinal axis of the drill is of generally S-shaped that is sinusoidal configuration.

[0086] The aforementioned parabolic flute form provides more area for chip removal when compared with the more standard flute shape.

[0087] The present invention by a combination of machining angles and grinding ranges provides a twist drill having exceptionally large flute areas for the passage therethrough of cut materials so that drilling operations can be performed at extremely high speeds.