A drill having a replaceable cutting head, modified to eliminate forces which would distort the pocket of the drill shank and otherwise concentrate stresses which would cause failure of the drill. The cutting head has a frustoconical depending connecting member received in a receptacle formed in the shank. In different embodiments, contact between the pocket formed in the shank and the cutting head connecting member is limited. In one embodiment, angle of drive surfaces is modified from prior art practice. In another embodiment, transition of at curved joints between vertical and horizontal surfaces is made more gradual. The drill preferably has flutes formed collectively by the shank and cutting head when assembled.
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0. 13. A replaceable cutting head for use with a shank for conducting rotary cutting operations on a work piece, the shank having a rotational axis, a driving surface, and a pocket having an internally facing surface, the replaceable cutting head comprising:
a rotational axis;
a cutting portion;
a driven surface structured to abut the drive surface of the shank and be rotated when the shank is rotated with the cutting head installed; and
an interlocking member structured to engage the pocket of the tool shank in a manner that retains at least a portion of the cutting head within the pocket, the interlocking member comprising:
a lateral surface oriented at an obtuse angle to the rotational axis of the cutting head and facing the cutting portion of the cutting head; and
an extension adjacent to the lateral surface and projecting away from the cutting portion of the cutting head.
0. 7. A cutting tool assembly for conducting rotary cutting operations on a work piece, the cutting tool assembly comprising: a tool shank and a replaceable cutting head which is installed on and engages the tool shank, the tool shank and the cutting head having a common rotational axis and mating peripheral surfaces when assembled together, the cutting tool assembly having a leading end which engages the work piece and a trailing end located oppositely from the leading end, relative to the rotational axis;
the cutting head having:
a cutting portion at the leading end of the cutting tool assembly;
a driven surface; and
an interlocking member comprising:
a lateral surface oriented at an obtuse angle to the rotational axis and facing the cutting portion of the cutting head; and
an extension adjacent to the lateral surface and projecting away from the cutting portion of the cutting head; and
the shank having:
a pocket including a pocket floor and an internally facing surface oriented to abut the lateral surface of the cutting head, the pocket being arranged to engage the interlocking member of the cutting head and retain the cutting head when the cutting head is installed within the pocket;
at least one abutment surface abutting the cutting head when the cutting head is installed within the pocket; and
at least one driving surface oriented to abut the driven surface of the cutting head and arranged to rotate the cutting head when the shank is rotated with the cutting head installed within the pocket.
1. A cutting tool assembly for conducting rotary cutting operations on a work piece, said cutting tool assembly comprising a tool shank and a replaceable cutting head which is installed on and engages the tool shank, the tool shank and the cutting head having a common rotational axis and mating peripheral surfaces when assembled together, the cutting tool assembly having a leading end which engages the work piece and a trailing end located oppositely from the leading end, relative to the rotational axis;
the shank having a pocket for coupling to the cutting head, an interlocking member arranged to retain the cutting head when the cutting head is installed within the pocket, at least one abutment surface abutting the cutting head when the cutting head is installed within the pocket, and at least one driving surface arranged to rotate the cutting head when the shank is rotated with the cutting head installed within the pocket;
the cutting head having a cutting portion at the leading end of the cutting tool assembly, an interlocking member engaging the interlocking member of the shank, and a driven surface oriented to abut the driving surface of the shank when the cutting head is installed within the pocket; wherein the interlocking member of the cutting head comprises a lateral surface oriented at an obtuse angle to the rotational axis and facing the cutting portion of the cutting head, and an extension adjacent to the lateral surface and projecting away from the cutting portion of the cutting head,
wherein the pocket of the shank has a floor portion and a surface that corresponds to the lateral surface of the cutting head, whereby the extension reinforces the interlocking member at the lateral surface oriented at an obtuse angle to the rotational axis such that stresses are minimized due to a smoother smooth transition between the dovetail surface of the pocket corresponding to the lateral surface of the cutting tool and the pocket floor portion of the pocket.
2. The cutting tool assembly according to
3. The cutting tool assembly according to
4. The cutting tool assembly according to
5. The cutting tool assembly according to
6. The cutting tool assembly according to
0. 8. The cutting tool assembly according to claim 7, wherein the extension adjacent to the lateral surface and projecting away from the cutting portion of the cutting head has a cylindrical outer surface.
0. 9. The cutting tool assembly according to claim 7, wherein the extension adjacent to the lateral surface and projecting away from the cutting portion of the cutting head has a tapered outer surface.
0. 10. The cutting tool assembly according to claim 7, wherein the pocket has at least one internally facing surface oriented to abut the lateral surface of the cutting head, the internally facing surface being dimensioned and configured to abut the lateral surface along part of the extent of the lateral surface and to avoid making contact along the balance of the lateral surface, whereby the uncontacted portion of the pocket allows for deflection of the pocket walls when forces are imposed on the pocket by the cutting head during cutting operations of the cutting tool, thereby mitigating radial deflection of the pocket walls.
0. 11. The cutting tool assembly according to claim 7, wherein the driving surface of the shank is disposed out of radial orientation with respect to the rotational axis such that the driving surface has a leading inner portion and a trailing outer portion, whereby resistive forces imposed by the cutting head during cutting operations acting perpendicularly against the driving surface have an inward component tending to compress the wall of the pocket inwardly during cutting operations, thereby opposing forces imposed the cutting head which would otherwise tend to spread open the pocket.
0. 12. The cutting tool assembly according to claim 7, further comprising a circumferential surface and two opposed flutes each projecting into the tool shank along the circumferential surface, wherein the pocket further comprises a first pocket wall and a diametrically opposed second pocket wall spaced apart from the first pocket wall and the pocket has a floor which separates and spaces apart the first pocket wall from the second pocket wall and which bears a relief trough projecting into the shank towards the trailing end of the cutting tool assembly and extending across and spanning the floor from one flute to the other flute, a first shelf extending laterally across the floor at an upper edge of the relief trough at the first pocket wall and a second shelf extending laterally across the floor at another upper edge of the relief trough at the second pocket wall, and the relief trough is angularly oriented relative to the rotational axis such that the first shelf intersects only one flute and the trough is disposed between the first shelf and the other flute, and the second shelf intersects only one flute and the trough is disposed between the second shelf and the other flute.
0. 14. The replaceable cutting head according to claim 13, wherein the extension adjacent to the lateral surface and projecting away from the cutting portion of the cutting head has a cylindrical outer surface.
0. 15. The replaceable cutting head according to claim 13, wherein the extension adjacent to the lateral surface and projecting away from the cutting portion of the cutting head has a tapered outer surface.
0. 16. The replaceable cutting head according to claim 13, wherein the driving surface of the shank is disposed out of radial orientation with respect to the rotational axis such that the driving surface has a leading inner portion and a trailing outer portion, whereby resistive forces imposed by the cutting head during cutting operations acting perpendicularly against the driving surface have an inward component structured to generally compress the wall of the pocket inwardly during cutting operations, thereby opposing forces imposed by the cutting head which would otherwise tend to spread open the pocket.
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The present invention relates to cutting tools, and more particularly to modular drills having replaceable cutting tips.
Drills having replaceable cutting tips are known. Illustratively, such tools are shown in U.S. Pat. Nos. 5,957,631 and 6,059,492, both issued to Gil Hecht on Sep. 28, 1999, and May 9, 2000, respectively. The subject drills have replaceable cutting heads which are mounted on shanks. The cutting heads and shanks display continuous and complementing configuration as fluted drills. To this end, each shank has structure for retaining and rotating an associated cutting head. The associated cutting head has complementing structure for being retained and rotated by the shank. While these devices will operate under some circumstances, closer analysis reveals that their useful lives are potentially unduly limited. More specifically, the retaining and drive structure of the shank is subject to deformation and failure during its service life due to concentration of stresses imposed during ordinary service.
The present invention provides modifications to drills having replaceable cutting tips, of the type shown in the above referenced patents to Hecht. The modifications of the present invention alter stresses imposed on the shanks such that the shanks either do not undergo deformation and outright failure while in service or alternatively, increase the service life achievable before deformation renders the tool unusable. These modifications generally connote prevention of direct contact of a replaceable cutting head with the shank at certain specified locations. Also, orientations of certain abutting surfaces are modified so that stresses are imposed differently from the original design of Hecht.
One specific example of modifications is that of providing a gap between a frustoconical dovetail formed in the cutting head and a cooperating recess formed in the shank, at the forward and rearward areas of mutual contact. The area of contact is limited to that portion between the forward and rearward areas of contact. A second modification is that of altering the angle of drive or torque transmission surfaces from purely radial to inclined relative to a purely radial direction. This has the effect of redistributing forces which would otherwise act on the walls of a pocket formed in the shank. The pocket, which receives the connection structure of the cutting head, then better resists distorting forces. A third modification is that of lengthening at the walls of that portion of the body forming a pocket which receives the cutting head and eliminating sharp corners in this region of the body. In still another modification, the floor of the pocket is modified in the manner of the third modification.
These modifications redistribute distorting forces away from portions of the shank which are more susceptible to distortion to portions of the shank better able to withstand these forces. The ultimate effect is to increase the useful service life of the shank due to reduced distortion of the pocket.
Further features of the present invention, as well as the advantages derived therefrom, will become clear from the following detailed description made with reference to the drawings in which:
The documents, patents and patent applications referred to herein, including those pertaining to the prior art, are hereby incorporated by reference in their entirety.
Once cutting head 14 is installed on shank 12, the flute collectively formed by cutting head flute portion 16 and shank flute portion 18 will align to form a flute in generally continuous and undistorted fashion. A similar flute is of course formed on the other side of cutting tool 10. Although two flutes are preferred, any number of flutes including only one is possible.
In the depiction of
That portion of shank 12 which couples to and rotates cutting head 14 is referred to as pocket 34. The principal elements of pocket 34 include two generally symmetrical and similar castellated wall sections 36, 38. Wall section 36 will be described, it being understood that wall 38 is a generally symmetrical counterpart thereof. Wall section 36 is essentially a continuation of the body of shank 12 which projects upwardly in the depiction of
Cutting head 14 has cutting edges (only cutting edge 54 is visible in
Any or all of central floor portion 40, faces 48 and 50, and faces formed in wall portion 38 corresponding to faces 48 and 50 serve as abutment surfaces which abut cutting head 14 when cutting head 14 is installed on shank 12.
Cutting head 14 has a shank connection portion opposite the cutting portion, or alternatively stated, facing the trailing end of cutting head 14, in the form of an interlocking member arranged to retain cutting head 14 within pocket 34 of shank 12. In the embodiment of
Faces 64, 66 may be stepped, or located at different levels or points along axis 20, in the same manner as and to correspond to the axial spacing apart of faces 48 and 50 of shank 12. Any or all of faces 64, 66 serve as abutment surfaces for abutting shank 12. Abutment of faces 64, 66 with their corresponding surfaces 48, 50 of shank 12 seats cutting head 14 on shank 12 responsive to compressive axial loading. When rotated into the interlocked position with respect to pocket 34, dovetail member 60 will engage interior frustoconical face 46 of pocket 34, thereby preventing disengagement in the axial direction away from shank 12.
It is an important feature of the invention that contact between frustoconical face 46 and frustoconical lateral surface 62 be limited such that contact not occur over the entire extent of face 46 or lateral surface 62. Rather, frustoconical face 46 and frustoconical lateral surface 62 are dimensioned and configured to abut mutually along part of the extent of surface 62 and to avoid making contact along the balance of lateral surface 62. This characteristic enables pocket 34 to experience minimized forces imposed thereon during cutting operations by cutting head 14, which forces would otherwise tend to spread or distort pocket 34. Alternatively stated, although tangential forces remain unchanged, forces imposing a radially outward component are minimized at critical areas. Pocket 34 is thus less subject to distorting forces which would otherwise cause pocket 34 to spread over time of use, thereby shortening the useful life of shank 12. Representative areas 70, 72 of non-contact between face 46 and surface 62 are shown stippled in
Non-contact of face 46 and surface 62 may be accomplished in several ways. Turning now to
Referring now to
The dovetail member is limited to an extent less than the full extent of the internally facing surfaces of the pocket when the cutting head is installed in the pocket. More particularly, it is presently preferred that the zone of contact extend along the interior of each of walls 124A and 126A within a range of about fifteen to about seventy-five degrees.
The aforementioned embodiments all relate to ways of limiting contact of a dovetail member with pocket walls. The effect of limiting contact in this manner is that the uncontacted portion of the walls of the pockets of the embodiments of
It would be possible to eliminate cylindrical surfaces 166, 170 from extension 158. As seen in
The effect of the modifications of the embodiments of
Turning now to
A consequence of this geometry is that trough 206 has at one end a curved end edge 210 which meets the side profile 214 of dovetail member 198 (see
It will be appreciated that while the dovetail portion of the connector of the cutting head is described in terms of being frustoconical, it would be possible to utilize any configuration wherein there is an upwardly facing surface which can engage one or more corresponding surfaces formed in the retaining structure of the shank. It is preferred to form the dovetail of the connector as frustoconical merely because rotary machining and other inexpensive methods may be employed to form the dovetail.
The novel features presented herein may be present in combinations within a single tool made according to the present invention, where such embodiments are geometrically compatible, for example surface 221 also reduces the contact area between the dovetail and the pocket.
It will further be appreciated that relative locations of connecting and drive structure of the cutting head and of the shank may be reversed if desired, with appropriate accommodation being made to account for differences in the directions in which forces are imposed.
While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.
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