Patent Application
20080084106
The following is a brief description of the drawings that form a part of this patent application:
Referring to the drawings,
The cutting tool body 22 has an axial forward end 24 and an axial rearward end 26. A hard insert 30 is affixed (such as by brazing or the like) in a socket (not illustrated) in the axial forward end 24 of the cutting tool body 22. Hard insert 30 is typically made from cemented carbide such as, for example, cobalt cemented tungsten carbide wherein U.S. Pat. No. 6,375,272 to Ojanen discloses acceptable grades of cemented (cobalt) tungsten carbide. The geometry of the hard insert 30 can vary depending upon the specific application. U.S. Pat. No. 4,497,520 B2 to Ojanen and U.S. Pat. No. 6,375,272 to Ojanen each disclose an exemplary geometry for the hard insert. It should be appreciated that as an alternative to the socket, the axial forward end of the cutting tool body may present a projection that is received within a socket in the bottom of the hard tip. This alternate structure can be along the lines of that disclosed in U.S. Pat. No. 5,141,289 to Stiffler wherein this patent is hereby incorporated by reference herein. Applicant points out that U.S. Pat. No. 5,141,289 also discloses braze alloys that typically are used to braze the hard tip to the socket in the cutting tool body.
The cutting tool body 22 is divided into three principal portions; namely, a head portion, a collar portion and a shank portion. These portions will now be described.
The most axial forward portion is a head portion (see bracket 32). Beginning at the axial forward end 24 and extending along longitudinal axis L-L in the axial rearward direction for a distance A, the head portion 32 comprises a cylindrical section 34 followed by a frusto-conical section 36. As one can appreciate, the transverse dimension (or diameter) of the frusto-conical section 36 increases as the frusto-conical section 36 moves in an axial rearward direction.
The mediate portion is the collar portion (see bracket 38). Beginning at the juncture with the head portion 32 and extending along the longitudinal axis L-L in the axial rearward direction for a distance B, the collar portion 38 comprises a cylindrical section 40 followed by a beveled section 42. The collar portion 38 has an axial forward facing surface 57 and an axial rearward facing surface 58. It should be appreciated that the cylindrical section 40 presents the maximum transverse diameter (or diameter) of the cutting tool body 22.
The most axial rearward portion is the shank portion (see bracket 44). Beginning at the juncture with the collar portion 38 and extending along the longitudinal axis L-L in the axial rearward direction for a distance C, the shank portion 44 comprises a generally cylindrical section 46 followed by a beveled section 48 followed by a forward cylindrical tail section 50, followed by a retainer groove 52 followed by a rearward cylindrical tail section 54 and terminating in a beveled section 56. As is known by those skilled in the art, the shank portion 44 is the portion of the cutting tool body 22 that carries the retainer (not illustrated). The retainer rotatably retains the rotatable cutting tool in the bore of the holder (or the bore of the sleeve carried by a holder). While the retainer can take on any one of many geometries, a retainer suitable for use with this cutting tool body is shown and described in U.S. Pat. No. 4,850,649 to Beach et al.
The cutting tool body 22 presents a hardness profile such that there are three hardness regions; namely, an axial forward hardness region, a transition hardness region, and an axial rearward hardness region. Each one of these hardness regions will be described in more detail hereinafter.
In reference to the axial forward hardness region (see bracket 60), this region begins at and extends along the longitudinal axis L-L in the axial rearward direction a distance D. It should be appreciated that axial distance D is greater than axial distance A, which is the axial length of the head portion 32. What this means is that the axial forward hardness region 60 extends in the axial direction to such an extent to encompass the entire head portion 32, as well as an axial forward section of the collar portion 38.
The axial forward hardness region 60 of the cutting tool body 22 has a minimum first hardness value. In other words, every part of the axial forward hardness region 60 exhibits a hardness value greater than or equal to the minimum (or first) hardness. The minimum (or first) hardness value is pre-selected in that the appropriate part of the cutting tool body 22 (i.e., the axial forward hardness region) can be manufactured to have a hardness equal to or greater than this minimum (or first) hardness. In general, a surface with a higher hardness will possess a greater wear resistance. Hence, by making the head portion 32 with a hardness greater than the pre-selected minimum (or first) hardness, the head portion 32 one provides pre-selected minimum wear resistance properties. Since the head portion 32 typically experiences the greatest abrasive wear during operation, it is desirable to provide the rotatable cutting tool with a head portion that has a higher hardness.
In reference to the transition hardness region (see bracket 62), this region begins at the juncture between the axial forward hardness region 60 and the transition hardness region 62 and extends along the longitudinal axis L-L in the axial rearward direction a distance E. It should be appreciated that axial distance E is of such a length that the transition hardness region 62 has its axial rearward termination in the shank portion 44. By doing so, the transition hardness region 62 encompasses an axial rearward section of the collar portion 38 and an axial forward section of the shank portion 44. It is also apparent that the transition hardness region 62 also encompasses the axial rearward facing surface 58 of the collar portion 38.
The transition hardness region 62 has hardness values within a selected range, as well as a second average hardness. The second average hardness of the transition hardness region 62 is less than the first average hardness of the axial forward hardness region 60. The hardness of transition hardness region 62 is less than or equal to the minimum hardness of the axial forward hardness region 60. In general, the hardness of the transition hardness region 62 decreases in the axial rearward direction.
In reference to the axial rearward hardness region (see bracket 64), this region begins at the juncture between the transition hardness region 62 and the axial rearward hardness region 64 and extends along central longitudinal axis L-L a distance F to the axial rearward end 26 of the cutting tool body 22.
The axial rearward hardness region 64 has hardness values within a pre-selected range, as well as a third average hardness, which is less than the second average hardness. The hardness of the axial rearward hardness region 64 may on occasion overlap the hardness in the transition hardness region 62; however, in general, the hardness in the axial rearward hardness region 64 is less than or equal to the hardness in the transition hardness region 62. In general, the hardness of the axial rearward region 64 can decease in the axial rearward direction. However, it should be appreciated that the portion of the cutting tool body 22 in the vicinity of the retainer groove 52 could have the lowest hardness value of any location on the cutting tool body 22.
As can be appreciated, the shank portion 44 experiences extreme stress (or load) during operation in a severe environment. Since the shank portion 44 has a lower pre-selected average hardness, the shank portion 44 displays an increased level of toughness. Such a level of toughness will allow the shank portion to withstand the stresses it undergoes during operation in a severe environment. It is thus desirable to provide a rotatable cutting tool with a shank portion that has toughness to withstand operational stresses.
The transition hardness region 62 provides for a gradual transition in hardness between the axial forward hardness region 60, which provides for desirable wear-resistance, and the axial rearward hardness region 64, which provides for desirable toughness. Such a gradual transition eliminates a sudden change in hardness and thereby helps maintain the integrity of the rotatable cutting tool during operation.
Referring to the drawings,
The cutting tool body 72 has an axial forward end 74 and an axial rearward end 76. A hard insert 80 is affixed (such as by brazing or the like) in a socket (not illustrated) in the axial forward end 74 of the cutting tool body 72. Hard insert 80 is typically made from cemented carbide such as those grades described above in connection with the first specific embodiment. The geometry of the hard insert 80 can vary depending upon the specific application such as described above in connection with the first specific embodiment.
The cutting tool body 72 is divided into three principal portions; namely, a head portion, a collar portion and a shank portion. These portions will now be described.
The most axial forward portion is a head portion (see bracket 82). Beginning at the axial forward end 74 and extending along central longitudinal axis N-N in the axial rearward direction for a distance G, the head portion 82 comprises the following sections: a frusto-conical section 84 followed by another frusto-conical section 86 followed by a cylindrical section 88 and ending in a puller groove 90.
The mediate portion is the collar portion (see bracket 94). Beginning at the juncture with the head portion 82 (i.e., the axial forward facing surface 116) and extending along the longitudinal axis N-N in the axial rearward direction a distance H, the collar portion 94 comprises a cylindrical section 96 followed by a beveled section 97. The collar portion 94 has an axial forward facing surface 116 and an axial rearward facing surface 114.
It is apparent that the cylindrical section 88 and the cylindrical section 96 each present the maximum transverse dimension of the cutting tool body 72. The puller groove 90 separates the cylindrical sections (88 and 96). The puller groove functions in conjunction with a puller tool to extract the rotatable cutting tool from the bore of the holder (or the bore of the sleeve). A puller tool is known to those skilled in the art.
The most axial rearward portion is the shank portion (see bracket 98). Beginning at the juncture with the collar portion 94 and extending along the longitudinal axis N-N in the axial rearward direction a distance I, the shank portion 98 comprises a cylindrical section 100 followed by a beveled section 102 followed by a forward cylindrical tail section 104, followed by a retainer groove 106 followed by a rearward cylindrical tail section 108 and terminating in a beveled section 110. Retainers useful in conjunction win cutting tool body 22 are also useful in conjunction with cutting tool body 72.
The cutting tool body 72 presents a hardness profile such that there are three hardness regions; namely, an axial forward hardness region, a transition hardness region, and an axial rearward hardness region. Each one of these hardness regions will be described in more detail hereinafter.
In reference to the axial forward hardness region (see bracket 118), this region begins at the axial forward end 74 and extends along longitudinal axis N-N in the axial rearward direction a distance J. It should be appreciated that axial distance J is greater than axial distance G, which is the axial length of the head portion 82. What this means is that the axial forward hardness region 118 extends in the axial direction to such an extent to encompass the entire head portion 82, as well as an axial forward section of the collar portion 94.
The axial forward hardness region 118 of the cutting tool body 72 has a minimum first hardness value. In other words, every part of the axial forward hardness region 118 exhibits a hardness value greater than or equal to the minimum (or first) hardness. The minimum (or first) hardness value is pre-selected in that the appropriate part of the cutting tool body 72 (i.e., the axial forward hardness region) can be manufactured to have a hardness equal to or greater than this minimum (or first) hardness. In general, a surface with a higher hardness possesses greater wear resistance. Hence, by making the head portion 82 with its hardness greater than the pre-selected minimum (or first) hardness, the head portion 82 exhibits pre-selected minimum wear resistance properties for the rotatable cutting tool 70.
In reference to the transition hardness region (see bracket 120), this region begins at the juncture between the axial forward hardness region 118, and the transition hardness region 120 and extends along longitudinal axis N-N in the axial rearward direction a distance K. It should be appreciated that axial distance K is of such a length that the transition hardness region 120 has its axial rearward termination in the shank portion 98. By doing so, the transition hardness region 120 encompasses an axial rearward section of the collar portion 94 and an axial forward section of the shank portion 98. It is also apparent that the transition hardness region 120 also encompasses the axial rearward facing surface 114 of the collar portion 94.
The transition hardness region 120 has hardness values within a selected range, as well as a second average hardness. The second average hardness of the transition hardness region 120 is less than the first average hardness of the axial forward hardness region 118. The hardness of the transition hardness region 120 is less than or equal to the minimum hardness of the axial forward hardness region 118. In general, the hardness of the transition hardness region 120 decreases in the axial rearward direction.
In reference to the axial rearward hardness region (see bracket 122), this region begins at the juncture between the transition hardness region 120 and the axial rearward hardness region 122 and extends along the longitudinal axis N-N a distance M to the axial rearward end 76 of the cutting tool body 72.
The axial rearward hardness region 122 has hardness values within a selected hardness range, as well as a third average hardness, which is less than the second average hardness. The hardness of the axial rearward hardness region 122 may on occasion overlap the hardness in the transition hardness region 120; however, in general, the hardness in the axial rearward hardness region 122 is less than or equal to the hardness in the transition hardness region 120. In general, the hardness of the axial rearward region 122 can decease in the axial rearward direction. However, it should be appreciated that the portion of the cutting tool body 72 in the vicinity of the retainer groove 106 could have the lowest hardness value of any location on the cutting tool body 72.
As can be appreciated, the shank portion 98 experiences extreme stress during operation in a severe environment. Since the shank portion 98 has a lower pre-selected average hardness, the shank portion 98 displays an increased level of toughness. Such a level of toughness will allow the shank portion to withstand the stresses it undergoes during operation in a severe environment. It is thus desirable to provide a rotatable cutting tool with a shank portion that has a toughness to withstand the operational stresses.
The transition hardness region 120 provides for a gradual transition in hardness between the axial forward hardness region 118, which provides for desirable wear-resistance, and the axial rearward hardness region 122, which provides for desirable toughness. Such a gradual transition eliminates a sudden change in hardness and thereby helps maintain the integrity of the rotatable cutting tool during operation.
Referring to
In regard to the manufacturing steps to make a cutting tool body (22 or 72), the first step comprises the formation of the pre-treatment basic steel cutting tool body. The pre-treatment cutting tool body can be forged including the socket to receive the hard insert. One method of forging the steel cutting tool body is shown and described in pending U.S. patent application Ser. No. 11/259,183 filed on Oct. 26, 2005 for a Cold-Formed Rotatable Cutting Tool And Method Of Making The Same by Randall W. Ojanen, and assigned to Kennametal Inc., the assignee of the present patent application. In the alternative, the cutting tool body can be machined to the desired geometry including the puller groove and the socket that receives the hard insert.
The second step is to position the braze shim (and flux) and the hard insert in the socket. The entire assembly including all of the steel cutting tool body is then induction heated to braze the hard insert into the socket. The hot assembly is then quenched in a polymer solution to harden the entire cutting tool body to the minimum hardness value for the axial forward hardness region.
The third step is to induction heat only the axial rearward portion of the cutting tool body. The part is then air cooled to room temperature. Since the impact of the heating of the axial rearward portion diminishes in the axial forward direction, it can be appreciated that the hardness of the axial forward hardness region will not be impacted (i.e., reduced) while the hardness in the transition hardness region will be impacted (i.e., reduced) less than in the axial rearward hardness region. The hardness in the axial rearward hardness region will be impacted (or reduced) the most.
One should appreciate that a difference between the prior art rotatable cutting tool body of
In this regard, in the prior art
Pursuant to this invention, Inventive Example 1 is a cutting tool body made from 15B37H Modified steel. The geometry of the cutting tool was along the lines of that shown in
Pursuant to this invention, Inventive Example 2 is a cutting tool body made from 15B37H Modified steel. The geometry of the cutting tool was along the lines of that shown in
It can be appreciated from the hardness values set forth in Table 1 and Table 2 that the entire head portion and the axial forward facing surface of the collar has a higher hardness, which provides for better wear resistance in the head portion that experiences abrasive wear. It can also be appreciated that the shank portion has a lower hardness, which provides for better toughness in the shank region that experiences stresses under severe operating environments.
It should be appreciated that the present invention provides a cutting tool body that exhibits improved resistance to abrasive wear. A more wear-resistant cutting tool body is better able to withstand severe wear conditions, and thereby is less likely to experience premature failure due to premature (or excessive) wear.
In order to provide an improved useful tool life, it would be desirable to provide a cutting tool body that exhibits improved toughness. A tougher cutting tool body is better able to withstand severe operating conditions, and thereby is less likely to experience premature failure (e.g., catastrophic stress fracturing) due to operational stress.
As one can appreciate, if a cutting tool body does not exhibit sufficient wear resistance or toughness there exists the risk that the cutting tool body may prematurely fail. Such a premature failure of the cutting tool body is an undesirable result that typically leads to the termination of the useful life of the rotatable cutting tool, as well as a decrease in the operational efficiency of the road milling machine. It thus is apparent that it would be very desirable to provide an improved rotatable cutting tool that has an improved cutting tool body wherein the cutting tool body exhibits improved wear resistance and improved toughness.
The patents and other documents identified herein are hereby incorporated by reference herein.
Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification or a practice of the invention disclosed herein. It is intended that the specification and examples are illustrative only and are not intended to be limiting on the scope of the invention. The true scope and spirit of the invention is indicated by the following claims.
