WO2008014367A1

WO2008014367A1 - Cutting tool with replaceable tip

Info

Publication number: WO2008014367A1
Application number: PCT/US2007/074396
Authority: WO
Inventors: Robert E. Mckinley; Timothy G. Stokey
Original assignee: Allied Machine & Engineering Corp.; Stokey, Steven, R.
Priority date: 2006-07-26
Filing date: 2007-07-26
Publication date: 2008-01-31

Abstract

A drill tool assembly comprises a drill insert and a tool body. The drill insert is demountably attached to the tool body by a threaded engagement. The threaded engagement is positioned above a seating surface of the insert in the tool body.

Description

CUTTING TOOL WITH REPLACEABLE TIP

Technical Field

[0001] The present invention relates to a cutting tool assembly for rotary cutting and/or machining, comprising a tool body and a replaceable cutting tip insert. More particularly, the present invention relates to a cutting tool having a replaceable cutting tip insert retained in position on a tool body by a pilot boss and a unique rotary wedge interface between the cutting tip insert and the tool body.

Background of the Invention

[0002] It is previously known to provide rotary cutting tools, such as drills, with replaceable cutting heads or drill tip inserts. These tips have been retained on a tool body by many methods including radial set screws secured through lands provided on the tool body, interference fit connections using dove-tail profiles, axial screws and drawbars, etc. While each method has different advantages and disadvantages, none of these tools can be easily and quickly replaced while maintaining optimized torque transferability, high feed rates, and a secure mounting to the tool body. Some prior tools of this type have worked well but have not been generally usable in aggressive machining operations, which produce high stress on the connection of the cutting head to the tool body.

[0003] Several examples of prior art configurations use a dovetail profile to connect the cutting tip or head to the tool body. A portion of the cutting head is inserted into a recess generally having at least one radial base surface. The cutting head is then rotated such that a dovetail profile on the cutting head engages a dovetail recess of the tool body. This engagement is typically an interference fit type arrangement such that the cutting head is prevented from rotating in a disengaging direction, hi order for the interference fit to provide sufficient retaining force, high stresses result at the tool body interface with the cutting head. Prior art tool bodies of this type have been susceptible to fatigue in the clamp arms about the recess such that the tool loses clamping force and can no longer retain the cutting head. In addition, the dovetail connection is typically below the seating surface of the cutting head which creates a cantilever at the tip with a relatively long moment arm. This may result in a significant decrease in the stability of the tool. Another problem with a dovetail connection is that the feed force during operation of the tool pushes the cutting head downward into the tool body, which can lessen the retaining force of the dovetail connection and permit the cutting head to loosen. [0004] Other examples of connecting the cutting head use an axial engagement bar to secure the cutting head to the tool body. Although attempting to clamp the head to the body, the high stress at the interface again may result in loosening of the connection and/or make the tool susceptible to eccentric and other loads. The axial engagement bar system also adds additional pieces and cost to the tool.

[0005] It is also found in various tools with replaceable cutting heads, that it may be impossible to change the cutting head while the tool is mounted in an associated tool holder or machine. Thus, it is required that the entire tool be removed from the tool holder or machine, the cutting head then being replaced, and the tool being reintroduced into the machine for continued operation. Such a process adds labor and time, and detracts from the advantages of having the replaceable insert, and from the machining speeds achievable.

[0006] Accordingly, there remains a need in the art for a new drill assembly utilizing a replaceable cutting tip which combines the advantages of a replaceable cutting tip with the ability to be used in aggressive machining operations in which high stress conditions will exist. There also remains a need to provide drill assembly utilizing a replaceable cutting head which allows the cutting head to be replaced while the tool is mounted in the tool holder or machine to simplify and speed up this process.

Summary of the Invention

[0007] A drilling tool assembly is provided having a replaceable cutting tip which provides one or more improvements over the prior art. These and other advantages of the present invention will be apparent in a review of the drawings and the detailed description of the drawings. Brief Description of the Drawings

[0008] FIG. 1 is an exploded perspective view of a first embodiment of the cutting tool assembly of the present invention along its longitudinal axis A;

[0009] FIG. IA is an exploded perspective view of an alternate example of the invention along its longitudinal axis A;

[00010] FIG. 2 is a detail exploded perspective view of the cutting head and leading end of the tool body in accordance with the present invention of Fig. 1 ;

[0010] FIG. 3 is a detail view of the leading end of the tool body in accordance with the present invention of Fig. 1 ;

[0011] FIGS. 4A-4D are a side view, a bottom view, a top view, and an end view, respectively, of the cutting tip in accordance with the present invention of Fig. 1; [0012] FIG. 5 is an exploded perspective view of a second embodiment of the cutting tool assembly of the present invention along its longitudinal axis A;

[0013] FIG. 6 is a detail exploded perspective view of the cutting head and leading end of the tool body in accordance with the present invention of Fig. 5;

[0014] FIG. 7 is a detail view of the leading end of the tool body in accordance with the present invention of Fig. 5;

[0015] FIGS. 8A-8D are a side view, a bottom view, a top view, and an end view, respectively, of the cutting tip in accordance with the present invention of Fig. 5; [0016] FIG. 9 is a detail exploded side view of a third embodiment of the cutting tool assembly of the present invention along its longitudinal axis;

[0017] FIG. 10 is a detail exploded perspective view of the cutting head and leading end of the tool body in accordance with the present invention of Fig. 9;

[0018] FIG. 11 is a perspective view of the assembled cutting head and leading end of the tool body in accordance with the present invention of Fig. 9;

[0019] FIG. 12 is a detail exploded side view of another embodiment of the cutting tool assembly of the present invention along its longitudinal axis;

[0020] FIG. 13 is a detail exploded perspective view of the cutting head and leading end of the tool body in accordance with the present invention of Fig. 12; and [0021] FIG. 14 is a perspective view of the assembled cutting head and leading end of the tool body in accordance with the present invention of Fig. 12.

Detailed Description of the Drawings

[0022] Referring now to the drawings, wherein similar reference characters designate corresponding parts throughout the several views, there is generally indicated at 10 and 10' a cutting tool assembly according to a first embodiment and a second embodiment of the present invention, for use in drilling operations. A third and fourth embodiment are indicated at 110 and 110' of the present invention. Referring now to FIG. 1, cutting tool assembly 10 having a longitudinal and rotational axis A, comprises a replaceable cutting insert or cutting tip 12 and a tool body 14 formed on a tool shank 16. The cutting insert 12 and the tool body 14 are formed with chip flute sections 20, and 22, respectively, that, when the cutting tool is assembled, form continuous flutes which extend from a cutting edge 24 on the leading end of the cutting insert 12 to the trailing end 26 of the tool body 14. While the flutes shown are helical, it is also contemplated that a straight flute or a combination flute having a helical portion and a straight portion could also be used herein. The tool body 14 may also include flush channels or lubrication vent 60, which allows the application and flow of lubrication toward the drill insert 12 to facilitate the drilling operation. The flush channels 60 may be formed through the tool body to correspond with the type of flutes. Although not shown, the flush channels 60 may also be formed through the cutting insert 12.

[0023] The connection features of the cutting insert 12 and the tool body 14 are better shown in FIG. 2. The tool body 14 has a receiving area machined to accept the insert 12. The receiving area of the tool body 14 comprises a holder slot 30, which may extend across the entire diameter of the tool body 14 or, at least, over a center portion thereof at the general location of the rotational axis A of tool body 14. The holder slot 30 has a bottom wall or locating surface 32 positioned in substantially perpendicular orientation relative to the rotational axis A of the tool body 14. An aperture or bore 34, which is positioned precisely with respect to the axis A and extending downwardly from the locating surface 32 of slot 30. [0024] The cutting insert 12 may comprise a generally cylindrical pilot boss 42 forming a trailing end of the insert 12 and extending from a seating surface 44 of the insert 12. The pilot boss 42 engages the bore 34 in the bottom wall 32 of the slot 30. This confines the insert 12 within the tool body 360 degrees radially and precisely positions the insert 12 in tool body 14. This pilot boss 42 and bore 34 engagement can be a close fit, interference fit, or taper fit. [0025] The tool body 14 further comprises a pair of driving lugs or arms 36 on either side of the slot 30. The driving lugs 36 each are formed with a drive surface 38 extending generally radially outward to a periphery of the tool body 14. The drive lugs 36 also comprise a generally cylindrical surface, or central surface 50, on a radially inward side of the lug, which includes a means 52 for retaining the insert 12 on the tool body 14 as discussed in greater detail below. [0026] Once the pilot boss 42 is engaged and the seating surface 44 of the insert 12 is brought into contact with the locating surface 32 of the tool body 14, the insert 12 is then rotated until each driving surface 46 of the insert 12 registers against each of the driving lugs 36. The driving lugs 36 receive the torsional load of the insert 12 as it cuts, or drills, material. As the insert 12 is rotated, the means 52 for retaining the insert 12 engages the insert 12. The means 52 of retaining the insert 12 in the tool body 14 may be accomplished by a thread 40 formed in the driving lugs 36 and a corresponding thread 48 on a generally cylindrical surface portion 53 on the central portion 54 of the insert 12. As shown in FIG. 2, the threads 40 on the tool body 14 are single female threads 40 and the threads 48 on the insert 12 are formed as corresponding single male threads 48.

[0027] An alternate example is shown in FIG. IA, where the cutting tool assembly 10 has a slot 15 formed in the tool body 14, which is formed along the rotational axis A. As in the example of FIGS. 1 and 2, the cutting insert 12 and the tool body 14 are formed with chip flute sections 20, and 22, respectively, that, when the cutting tool is assembled, form continuous flutes which extend from a cutting edge 24 on the leading end of the cutting insert 12 to the trailing end 26 of the tool body 14. The slot 15 is positioned between the pair of driving lugs or arms 36 on either side of the slot 30, and extends into the chip flute section of the tool body 14. The flutes may be helical, and the slot 15 may also be configured to extend helically. Alternatively, it is also contemplated that a straight flute or a combination flute having a helical portion and a straight portion could be used, with the slot 15 designed to match the flute configuration in an example. The slot 15 is provided to allow the driving lugs or arms 36 to slightly deflect from one another upon high stresses being applied to the cutting insert 12. The slot 15 may also terminate with a stress relieving portion 17. Other aspects of the system may be similar to that described with reference to FIGS, land 2.

[0028] The single female thread form 40 of the tool body 14 is best shown in FIG. 3. The thread 40 has a lead angle λ, a helix angle ψ, and a thread angle α. The thread also may have a dimple or irregularity 56 formed on the thread 40 to help lock the insert 12 in place and help prevent an unintended rotation of the insert 12 in the removal direction.

[0029] Referring now to FIGS. 4A-4D, the cutting insert 12 is shown in greater detail. As previously discussed, cutting insert 12 comprises cutting edges 24 on a leading or cutting end of the insert 12 and pilot boss 42 on the trailing end protruding from seating surface 44. The pilot boss 42 may also have a secondary boss 62 protruding therefrom. The driving surface 46 extends radially from the central portion 54 of the insert 12. Although shown as a planar surface perpendicular to the longitudinal axis A, it is contemplated that the driving surface 46 could also be configured as a stepped or angled driving surface or as a convex/concave driving surface. The radially outermost portion of the insert forms a land 64 which corresponds to the periphery of the tool body 12. A helical margin 66 is formed on the rotationally leading side of the land 64 generally adjacent the flute 20 and the cutting edge 24 of the insert 12. The flute 20 may include a secondary flute 18 which creates a discontinuity with the flute 20 and helps in chip formation during cutting operations. A clearance surface 68 trails each cutting edge 24 on the leading end of the insert 12. The clearance surfaces 68 meet at the center of the insert 12 to form a chisel 70 across the web. Web thinning notches 72 are formed on either side of the chisel 70. The central portion 54 of the insert 12 shows the means 52 for connection of the insert 12 to the tool body 14 in the form of a single thread 48 on the generally cylindrical surface portion 53 on either side of the central portion 54. The thread 48 generally corresponds in shape to the thread 40 on the tool body. The cutting insert 12 is typically made of a hard material, such as cemented carbide, however, it is also contemplated that the insert could be made of a high-speed steel, ceramic material or any other suitable material. [0030] Referring again to FIG. 2, the threads 40, 48 are timed, or positioned, in such a way as to provide compressive force to the insert 12 and tensional force to the tool body 14. The engagement of thread forms 40, 48 occurs as the insert 12 is rotated towards the driving lugs 36 of the drill body 14. The thread forms 40, 48 make contact prior to the contact between the insert driving surface 46 and the tool body drive surface 38. As the insert 12 is forced to rotate against the driving lugs 36 of the tool body 14, the thread engagement compresses the seating surface 44 of the insert 12 against the locating surface 32 of the tool body 14 through the wedging action of the threads 40, 48. Once contact with the driving faces 38, 46 is accomplished, the preload of the compressive and tensioning forces established between the insert 12 and the tool body 14 retain the insert in place with respect to the holder during operation of the tool 10. The single thread shape results in a single surface of contact between each lug 36 and the central portion 54 of the insert 12. This configuration allows the compressive forces applied to the insert 12 to bear directly against the locating surface 32 of the tool body 14 and to eliminate any shear forces on the insert thread portion as may be possible with other configurations. The combination of these structures work synergistically to provide a connection which effectively removes any relative movement between the cutting head 12 and tool body 14, resulting in an assembled tool 10 which performs in the desired manner. [0031] Drill assembly 10 is intended to be used such that the cutting insert 12 can be replaced while the tool shank 16 remains in the tool holder (not shown). The method of replacing cutting head 12 comprises the steps of rotating the insert 12 in an opposite direction from that of assembly until the threads 40, 48 no longer engage and then axially removing the pilot 42 from the bore 34. It is contemplated that assembly and removal would be assisted by using a special tool (not shown) that fits over at least a portion of the insert 12 and will allow adequate torque to be applied manually by the machine operator.

[0032] A second embodiment of the present invention is shown in FIG. 5. Cutting tool assembly 10' comprises an insert 12' and tool body 14' that utilize a different means for connection. As shown in more detail in FIG. 6, the central portion 54' of the insert 12' is formed generally as a cylindrical surface and a single thread 48' protruding from a generally cylindrical surface portion 53' formed on the central portion 54'. The tool body 14' has a corresponding female central surface 50' with a single thread slot 40' formed therein.

[0033] The single female thread form 40' of the tool body 14' is best shown in FIG. 7. The thread 40' has a lead angle λ', a helix angle ψ', and a thread angle α'. The thread also may have a dimple or irregularity 56' formed on either side of the thread 40' to help lock the insert 12' in place and help prevent an unintended rotation of the insert 12* in the removal direction. [0034] Details of the insert 12' are best shown in FIGS. 8A-8D. The insert 12' generally corresponds to insert 12 other than the central portions. The central portion 54' of the insert 12' shows the means 52' for connection of the insert 12' to the tool body 14' in the form of a single thread 48' on the generally cylindrical surface portion 53' on either side of the central portion 54'. The thread 48' generally corresponds in shape to the thread 40' on the tool body. [0035] The procedure for connection of insert 12' to tool body 14' is identical to that discussed above with cutting tool assembly 10. However, the insert threads 48' are subject to shear forces which are not a factor in the first embodiment 10. The first embodiment 10 allows the compressive forces applied to the insert 12 bear directly against the locating surface 32 of the tool body 14 and eliminate any shear forces on the insert thread portion 48. [0036] A third embodiment of the present invention is shown in FIGS. 9-11. Cutting tool assembly 110 comprises an insert 112 and tool body 114 and is similar to cutting tool 10 except that cutting insert 112 has a different thread form and an additional relief in both the insert 112 and the tool body 114 as discussed in detail below. The procedure for connection of insert 112 to tool body 114 is generally the same to that discussed above with cutting tool assembly 10, 10'. As with the previous embodiments, cutting insert 1 12 comprises cutting edges 24 on a leading or cutting end of the insert 112 and pilot boss 42 on the trailing end protruding from seating surface 144. The insert 112 forms a land 64 which corresponds to the periphery of the insert body 112. Helical margin 66 is formed on the rotationally leading side of the land 64 generally adjacent the flute 20 and the cutting edge 24 of the insert 112. As with the previous embodiments, the flute 20 may include a secondary flute 118 which creates a discontinuity with the flute 20 and helps in chip formation during cutting operations. A driving surface 146 extends radially from the central portion forming the locator ears of the insert 112. It is possible when using a planar surface 46 such as shown in FIG. 2, that the driving surface 46 engages the surface 38 of the tool body 14 at a radially inward location. Referring back to FIG. 9, driving surface 146 is configured with a relief section 147, or scallop, to ensure that the insert 112 registers against tool body 114 at an outer radial location near the outer diameter of the insert 112 as this is the location where the maximum torsion loading occurs.

[0037] Another difference from the previous embodiments is in the threaded connection of the insert to the tool body. The insert 112 includes a means for connection of the insert 112 to the tool body 114 in the form of a thread 148 on either side of the insert 112. The thread 148 has a lead thread portion 161 and a trailing thread portion 163 that is generally a combination of the features of the previous embodiments. The thread 148 having the lead thread portion 161 and a trailing thread portion 163 is similar to thread 48', however, the cross-section, or distance between the lead thread portion 161 and the trailing thread portion 163 is more similar to the distance between thread 48 and the bottom seating surface 44 of the insert 12. The trailing thread portion 163 engages the thread form 140 of the tool body 114 when the insert 112 is disconnected to provide a smooth removal of the insert 112. However, as shown in FIG. 11, the trailing edge portion 163 of the thread 148 does not engage the thread form 140 of the tool body 114 when the insert 112 is fully attached to the tool body 114. This feature provides a relief area such that the compressive forces applied to the insert 112 bear directly against the locating surface 132 of the tool body 114 and eliminate any shear forces on the insert thread portion 148. It is also noted that the trailing edge portion 163 is spaced from the seating surface 144 for ease of manufacturing. By spacing the termination of the thread form 148 from the seating surface 144, it prevents any opportunity for mismatch of the two surfaces. It is also noted that the thread form 148 has larger radiuses at the interior and exterior corners than that of thread forms 48, 48' in order to help reduce stress concentrations and to ease manufacturing.

[0038] In all of the embodiments, the driving arms retain the insert on the tool body through an interference fit in which the top portion of the driving arms are deflected. In the third embodiment, the tool body 114 has also been modified as compared to the previous embodiments beyond the changes to the thread form 140. Referring now to FIG. 9, a relief 190 having a slot 192 and a terminal end 194 are shown formed in the driving arms 136 of the tool body 114. The slot 192 extends generally radially outward from the thread form 140 and then transitions generally in a longitudinal direction toward the leading end of the tool body 114. The slot 192 ends at the terminal end 194, shown herein as a circular form. The relief 190 reduces the amount of force required to deflect top portion of the driving arms 136 to retain the insert 112. This enables the tool body 114 to be manufactured of a stronger material that allows enhanced performance of the tool body 114 while retaining the insert assembly concept of the present invention.

[0039] The connection of the insert 112 to tool body 114 may be difficult and/or dangerous to accomplish by hand. The attachment/detachment force may be too great to overcome by hand and a user could cut their fingers on a sharp cutting edge 24. In order to help the operator to attach and remove the insert 112 from a tool body 114, it is contemplated that a tool (not shown) be used to engage the insert 112. Accordingly, insert 112 may be configured with indentions or slots 133 to allow the tool to engage the insert 112 for assembly and disassembly of the tool 110. The slots 133 are not limited to the shape as shown, however, it is preferred that the slots 133 be positioned on the periphery of the insert 112 between the cutting edge 24 and the driving surface 146.

[0040] Referring now to FIGS. 12-15, another embodiment of the present invention is shown of a tool 110' having the same insert 112 of the previous embodiment and a modified tool body 114'. In this embodiment, the body relief 190' is formed above the thread form 140' such that the slot 192' extends generally radially outward and then transitions generally in a longitudinal direction toward the trailing end of the tool body 114. The slot 192' ends at the terminal end 194', shown again herein as a circular form. As with the previous embodiment, the relief 190' reduces the amount of force required to deflect the portion of the driving arms 136' between the thread form 140' and the slot 192' to retain the insert 112. This enables the body to be manufactured of a stronger material that allows enhanced performance of the body while retaining the insert assembly concept of the present invention.

[0041] While the tool body relief 190 has been shown in tools 110 and 110'. The form of the relief 190, 190' is not intended to be limited to the configuration shown. It is contemplated that any number of different relief configurations are available and are included in the present invention.

[0042] While two embodiments 10, 10', 110, 110' are shown herein with different thread forms, the invention is not intended to be limited by the embodiments shown. It is contemplated that any number of different types of connections may be used herein without departing from the scope of the invention. The connection of the embodiments shown are basically a rotary wedges. The surfaces that are engaged, apply more force as rotation continues. The shape of the contact surfaces can take on any form that provides this compressive and tensional force. The thread form can take on any number of shapes and/or sizes. The thread forms can follow a single lead path or the thread forms may be symmetrical on each lug (as in the embodiments shown) since the total rotation is only approximately one-quarter turn and each thread form is independent of each other. The thread can be one thread engagement or multiple thread engagements. The thread lead or pitch can also be varied to apply more, or less compressive force over a given rotational engagement between the tool body and insert.

[0043] The connection of the present invention allows the drive lugs to be shorter than prior art tool bodies. The surfaces that are engaged apply more force as rotation continues. No separate holding mechanism or additional parts are required. In addition, the retention of the insert is accomplished near the leading end of the cutting insert as opposed to at the pilot as in prior art dove tail designs. This shortened distance increases the stability of the cutting tool by reducing the moment arm of the insert to the tool body. It is also contemplated that the pilot boss 42 and corresponding bore 34 may not be needed in a tool configuration where the central portion 54 of the insert 12 is made to precisely register against the corresponding central portion 50 of the body 14 to properly locate the insert.

[0044] Although the present invention has been described above in detail, the same is by way of illustration and example only and is not to be taken as a limitation on the present invention.

Claims

Claims:What is claimed is:

1. A drill tool assembly comprising a drill insert and a tool body wherein the drill insert is demountably attached to the tool body by a threaded engagement, wherein the threaded engagement is positioned above a seating surface of the insert in the tool body.