Cutting insert and retainer

An improved cutting tool insert for an assembly comprising a tool holder having an engagement pocket, the cutting insert configured generally as a polyhedral cutting element and adapted to engage the pocket in the tool holder, and a clamping member adapted to retain the insert in the pocket. A planar clamp bearing surface is formed in the insert oblique to the longitudinal, horizontal, and vertical axes of the insert such that pressure exerted by the clamping member on the bearing surface causes the insert to seat in the pocket and be held in place thereby.

FIELD OF THE INVENTION 
This application relates to a cutting tool and cutting tool holder, and 
more particularly, to means for securing the cutting tool to the tool 
holder. 
BACKGROUND OF THE INVENTION 
Tool holders and associated cutting tools are routine fixtures in today's 
industrial environment. For many applications, the most cost effective 
method of performing the cutting operation is to provide a sturdy, 
reusable cutting tool holder with a relatively inexpensive and disposable 
cutting tool insert. These inserts may be made of specialized metals 
suitable for performing the cutting operation, and are often equipped with 
carbide or diamond cutting tips. 
During the cutting operation, the insert is subjected to substantial 
vertical, horizontal, and lateral forces. To insure the close tolerances 
demanded in modern cutting applications, it is essential that the insert 
be secured against these forces. 
A number of systems have been developed for securing cutting tool inserts 
in associated holding devices. U.S. Pat. Nos. 4,669,924 and 4,545,705, 
issued to Benson, disclose a method for securing the cutting tool insert 
to the tool holder. Typically, a clamp having a beveled face engages a 
corresponding beveled surface in the cutting tool insert. The clamping 
member exerts a lateral force tending to squeeze the insert tightly 
against one side of the tool. This methodology, however, is not altogether 
satisfactory in that it does bring the insert into a secure holding 
relationship with the rear wall of the pocket in which the cutting tool 
insert is mounted and, accordingly, does not adequately secure the insert 
against forces acting in all three axes. 
A similar effort was made by Jones, et al, as shown in U.S. Pat. No. 
3,754,309. In this device, a vertical force is exerted against a diagonal 
slot in the tool insert, in an effort to reduce front to back motion of 
the cutting insert in the tool holder. Cutting tool inserts and clamps 
manufactured by the Sandvik Company utilizes similar engagement geometry 
between the clamping member and the insert. 
The prior art fails to adequately address the problem of holding the 
cutting inserts securely in place against forces acting in all three axes. 
Therefore, there is a need in the industry for a means of automatically 
positioning and securing a cutting tool insert against forces acting in 
all three axes. 
SUMMARY OF THE INVENTION 
The present invention comprises a generally polyhedral cutting tool insert 
adapted to be secured to the holder by the clamping member. The insert has 
a planar clamp bearing surface disposed obliquely to the longitudinal, 
horizontal, and vertical axes of the insert such that pressure exerted by 
a clamping member on the bearing surface causes the insert to seat in the 
holder and be held in place thereby against forces acting in all three 
major axes. 
According to the present invention, the cutting insert is formed with a 
recess communicating with both the top and one side surface of the insert. 
The plane comprising the bottom of the recess is oriented obliquely to 
both the top surface and side surface which it intersects. In the 
preferred embodiment, the resulting bearing surface faces slightly 
forward, toward the cutting end of the insert. 
An associated clamping member is removably affixed to a cutting tool. The 
cutting tool is provided with a pocket adapted to receive and engage at 
least one side, bottom and end surface of the cutting insert. The clamping 
member is provided with a wedge-shaped face, which is oblique to the top 
and one side surface of the insert, when the clamping member is in its 
clamped position. Further, the angle of the clamping face of the insert is 
selected to engage the recess of the insert so that downward pressure on 
the clamping member exerted by the clamp fastening screw is transmitted to 
the face of the recess of the insert, thereby driving the insert downward 
against the bottom of the pocket, inward against the side of the pocket 
and rearward against the back of the pocket, simultaneously. This 
simultaneous clamping force is transmitted without the requirement for 
precisely located front and rear walls of the recess, simplifying the 
manufacture of the insert, and eliminating breakage.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An overview of the invention will be apparent from a review of FIGS. 1 and 
2. A tool holder 10 is formed from a block of raw material, such as tool 
steel. The completed tool holder has a top surface 12, a bottom surface 8, 
a first side 6, and a second side 18. The base end 14 is typically held in 
an industrial cutting machine, so as to place the entire tool assembly 10 
in proximity to a workpiece. A working end 16 is disposed opposite the 
base end 14. The term "working end" is adopted to identify that end of the 
tool on which an actual cutting insert 30 may be mounted. 
An offset side wall 20 communicates with a pocket 23 in which the cutting 
tool insert 30 is held during the cutting operation. Clamp 24 engages 
insert 30, and is held in position by fastener 26. The completed assembly, 
therefore, comprises a tool holder 10, clamp 24 and cutting insert 30. The 
assembly is removably attached to an industrial cutting machine in such a 
fashion as to place the working end 31 of cutting tool 30 into contact 
with the workpiece being cut. 
A typical example of such a commercial cutting machine is a lathe, and a 
typical workpiece is a internal combustion engine piston. In such a 
cutting operation, an internal combustion engine piston would be mounted 
for high speed rotation along its cylindrical axes on the lathe spindles. 
The cutting tool assembly would then be brought into proximity with the 
workpiece, so as to cause the working end 31 of the cutting insert 30 to 
engage the workpiece, for example, for the purpose of cutting a groove in 
the circumference of the workpiece to accommodate a piston ring. The 
finished working end 31 of the insert 30 would be configured for the 
particular intended application, such as having a hardened cutting tip 
where the indentation on the working end 31 is shown in the drawings. 
As can be seen from FIG. 2, depending on the details of the cutting 
operation, including the direction of motion of the workpiece in relation 
to the cutting tool assembly, three dimensional forces are imposed on the 
cutting tool insert 30 during cutting operations. Along the x-axis, a line 
parallel to the longitudinal centerline of the tool holder, cutting 
operations may tend to pull the cutting tool insert away from the cutting 
tool holder in the x+ direction. Lateral forces tending to push the 
cutting tool toward the open side of the pocket can be said to be acting 
in the z+ direction. Finally, forces exerted by the workpiece against the 
cutting tool insert tending to raise the insert upward in the pocket can 
be said to be acting in the y+ direction. 
To contain the cutting tool insert against forces acting in the above three 
planes, the cutting tool insert 30 and clamp 26 are provided with novel 
engagement faces, as can be seen in more detail with reference to FIG. 2. 
By separating the components in an exploded view, the various features of 
the three main components comprising the tool assembly will be better 
understood. Again, the tool holder 10 comprises an essentially polygonal 
monolith, having a top surface 12, gripped base end 14, a working end 16, 
a bottom surface 8, a first side 6, a second side 18, and an offset side 
20, displaced from first side 16 by offset 21. A pocket 23 is formed 
proximate the working end 16 and offset side 20 of the tool holder 10. The 
pocket further comprises back surface 54, side surface 52 and bottom 
surface 50. A cross-section of the pocket 23, when viewed from the working 
end 16 of tool holder 12 is essentially rectangular, and corresponds in 
size and shape to the cross-section when viewed from the working end 31 of 
cutting tool insert 30. In this fashion, the top 41 of cutting tool insert 
30 engages the bottom surface 50 of pocket 23, the side surface 38 of 
cutting insert 30 engages the side surface 52 of pocket 23, and the rear 
surface 45 of cutting insert 30 engages rear surface 54 of the cutting 
tool holder 12. 
To secure insert 30 to tool holder 12, insert 30 is provided with a recess 
49 having a planar bearing surface 42 intersecting the side 36 of insert 
30, as well as the bottom 40 of insert 30. Surface 42 intersects the side 
36 of insert 30 at intersection 42a, and intersects the bottom 40 at 
intersection 42b. With further reference to FIG. 3, it can be seen that 
intersection 42b constitutes a line which is oblique to rear wall 45 of 
insert 30, and intersection 42a is similarly oblique to top surface 41 of 
insert 30. Thus, the surface 42 is disposed obliquely to the three major 
axes of the insert 30. 
After being placed into the pocket 23, insert 30 is secured against 
movement by the installation of clamp 24. A leg 29 of clamp 24 engages 
recess 28 formed in the tool holder 12. Recess 28 is oriented to insure 
engagement of the clamp with clamp bearing surface 42. Tool holder 12 is 
further provided with a threaded hole 21, suitable to engage a threaded 
fastener 26 which is passed through a hole 25 in clamp 24. Tightening of 
screw 26 brings clamping cam surface 27 into engagement with recessed 
bearing surface 42 of insert 30. Further tightening of screw 26 causes cam 
27 to exert pressure against face 42 as will be hereinafter explained. 
FIG. 3 presents a simplified view of clamp 24 and insert 30 as viewed from 
the side. Tool holder 10 is omitted for clarity. Clamp 24 can be viewed as 
a lever, functionally pivoting about pivot point 60 when leg 29 is 
inserted in the cavity 28 shown in FIG. 2. Downward pressure exerted by 
screw 26 urges both leg 29 and cam 27 downward toward insert 30. Because 
recess 28 is of limited depth, leg 29 seats against the bottom of recess 
28, restricting further downward movement of leg 29. Further, downward 
pressure on clamp 24 accordingly, is transmitted in the form of a downward 
rotational force of cam 27 against recess face 42. Because of the 
orientation of recess face 42 on insert 30, downward pressure from cam 27 
translates into simultaneous downward, sideward and rearward pressure of 
insert 30 in relation to the pocket. With reference to FIG. 1, these 
forces are transmitted in the x-, y- and z- directions, simultaneously. In 
this fashion, tightening of fastener 26 serves to seat the insert 30 in 
the pocket 23 against the respective surface and secure the insert 30 
against movement in all three axis. The sideward and downward forces 
exerted by cam 27 are transmitted to face 42 by cam face 27a, as depicted 
in FIG. 4. 
While, in the preferred embodiment, the recess 42 is formed in the insert 
30 in such a fashion as to create front recess wall 46 and rear recess 
wall 44, a benefit of the invention is the elimination of the need for 
either a front wall 46 or rear wall 44. Since the cam 27 transmits its 
securing forces to insert 30 by pressure of the cam face 27a against the 
recess face 42, rearward clamping forces in the x-direction are 
independent of any engagement of the clamp 24 with the insert recess rear 
surface 44. Likewise, insert 30 is formed of a size and shape to insure 
positive engagement of rear surface 38 of insert 30 with rear surface 54 
of tool holder 12, without the need for clamp 24 to engage a forward 
surface 46 of the tool insert. This feature, as shown in FIG. 4, allows 
for greatly simplified tool insert manufacture, without regard for exact 
placement of the tool insert recess 42. A more or less continuous recess 
face 42, as shown in FIG. 4, can be formed in insert 30, to position 
approximate the working end 34 of insert 30, while insuring positive 
engagement between the insert and the tool holder. 
With reference to FIG. 2, it has been shown that surface 42 is disposed 
obliquely to the three major axes of the insert to cause the insert to 
seat in the holder pocket and be held in place. In the most preferred 
embodiment the surface forms an angle to each axes in the range of 
20.degree.-45.degree. so as to divide the clamping force into components 
of generally similar magnitudes directed along the three axes. In one 
specific embodiment, the surface forms an angle of 38.degree. to the 
longitudinal (x) axis, 23.degree. to the vertical (y) axis, and 30.degree. 
to the horizontal (z) axis. Other combinations of angles within that range 
are equally possible.