Patent Description:
Holes may be created in materials using a variety of techniques including, but not limited to, orbital drilling and reaming. Both orbital drilling and reaming have individual advantages when creating holes in multi-layered assemblies such as the fuselage of an aircraft. Reaming, for example, has been shown to induce beneficial stresses in the wall of a hole. These beneficial stresses result in improved fatigue life of the hole. However, the reaming process creates burrs in the area around the drilled hole. The process of removing these burrs requires the removal of the material layers from an assembly stack. This process is time consuming and labor intensive in large structures such as an aircraft fuselage.

In contrast, orbital drilling allows for the creation of holes without the need to remove material layers from an assembly stack. This method of manufacture is commonly known as one-up assembly. Orbital drilled holes, however, typically experience a fatigue knockdown when compared to reamed holes. Such a fatigue knockdown is due to a reaming process inducing beneficial residual stresses in the wall of the hole that improve fatigue life, whereas an orbital drilling process cuts cleanly and leaves the machined surface in a neutral state of stress. Further, conventional drilling processes are more time consuming and labor intensive. As such, methods and systems for orbital drilling that induces residual stresses in the wall of the hole may be desirable.

<CIT> states, according to its abstract, that a cutter comprises a shank and a cutter body, wherein the shank and the cutter body are coaxial cylinders with a common axis as the center; the cutter body comprises two concentric cylinders; the first cylinder is arranged at the front end of the cutter body and the second cylinder is arranged at the rear end of the cutter body; the diameter of the first cylinder is smaller than that of the second cylinder; the first cylinder is provided with a first chip groove; the second cylinder is provided with a second chip groove; a first circumferential blade is formed at the junction of the first chip groove and the first cylinder; a second circumferential blade is formed at the junction of the second chip groove and the second cylinder; a stepped angle is used for transition from the first cylinder to the second cylinder; chamfered blades are arranged on an entity portion formed by the stepped angle and are arranged in the second chip groove; the first circumferential blade axially extends into the second cylinder; and end blades are arranged at the axial tail end of the first cylinder. The cutter has the following characteristic: the first chip groove and the second chip groove are independent of each other and are respectively designed according to the processing materials and conditions to ensure the maximization of the cutter performance.

<CIT> states, according to its abstract, that a drill bit includes a drill bit body having a central axis. A first cutting edge is disposed on the drill bit body at a first radial distance from the central axis as measured within a plane normal to the central axis. And a second cutting edge is disposed on the drill bit body at a second radial distance from the central axis as measured from within the plane. The first radial distance is less than the second radial distance.

<CIT> states, according to its abstract, that an end mill <NUM>, in which an angle of torsion - or + of a cutting edge is set to be <NUM> deg. -<NUM> deg. and a radius direction rake angle delta1, whose length (t) from the outside diameter phiD1 is <NUM>-<NUM>, is set to be a negative angle of -<NUM> deg. to -<NUM> deg. while a rake angle delta2 on a web thickness part side is set to be a positive angle, is used for rough cutting first, and then used for finishing work when the outside diameter of the cutting edge <NUM> is worn down to reach phiD2. When the outside diameter of the web thickness part is represented by phiD, it satisfies phiD=phiD2X(<NUM>-<NUM>), and when the outside diameter of a shank part is represented by phid, it satisfies phid<phiD1.

An enhanced cutting tool and orbital drilling system and methods of use are disclosed. The present disclosure provides a cutting tool with two cutting diameters. The first cutting diameter features positive rake geometries typical of regular orbital drilling or milling cutters that are designed for clean and efficient removal of the majority of material from the hole. The second set of teeth further down the tool feature negative radial rake angles designed to induce residual stresses in the wall of the hole.

A cutting tool according to claim <NUM> is provided comprising a body. The cutting tool also comprises a first portion of the body having a first diameter and a first radial rake angle. The cutting tool also comprises a second portion of the body adjacent the first portion, the second portion having a second diameter and a second radial rake angle, wherein the second diameter differs from the first diameter, and wherein the second radial rake angle differs from the first radial rake angle The first radial rake angle is <NUM> degrees and the second radial rake angle is negative <NUM> degrees.

Further, an orbital drilling system according to claim <NUM> is provided.

Still further, a method according to claim <NUM> is provided.

The following detailed description is exemplary in nature and is not intended to limit the disclosure or the application and uses of the embodiments of the disclosure. Descriptions of specific devices, techniques, and applications are provided only as examples. Modifications to the examples described herein will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other examples and applications without departing from the scope of the disclosure. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding field, background, summary or the following detailed description. The present disclosure should be accorded scope consistent with the claims, and not limited to the examples described and shown herein.

Embodiments of the disclosure may be described herein in terms of functional and/or logical block components and various processing steps. For the sake of brevity, conventional techniques and components related to aerodynamics, fluid dynamics, structures, control surfaces, manufacturing, and other functional aspects of the systems (and the individual operating components of the systems) may not be described in detail herein. In addition, those skilled in the art will appreciate that embodiments of the present disclosure may be practiced in conjunction with a variety of structural bodies, and that the embodiments described herein are merely example embodiments of the disclosure.

As would be apparent to one of ordinary skill in the art after reading this description, the following are examples and embodiments of the disclosure and are not limited to operating in accordance with these examples. Other embodiments may be utilized and structural changes may be made without departing from the scope of the exemplary embodiments of the present disclosure.

There are many different ways to form holes in a workpiece. Two of these ways are orbital drilling and reaming. Orbital drilling is based on rotating a cutting tool around its own axis and simultaneously around an offset center axis. Thus, the cutting tool can move simultaneously in an axial direction to drill or machine a hole and navigate horizontally (like a router tool) to machine an opening or cavity larger than the tool's diameter. By calculating an offset, and moving the spinning tool in a circular motion, a single cutting tool can be used to drill holes of any diameter larger than the tool's diameter. This can substantially reduce cutting tool inventory and tool changeover frequency. Orbital drilling systems make it possible to drill a complex-shaped hole and perform finishing operations with the same diameter tool and setup. Orbital drilling systems also allow manufacturers to create holes in multiple layers of materials without the need to remove material layers from the assembly stack (this process is commonly referred to as one-up assembly. Thus, the need for specific tools for additional tasks is greatly reduced because orbital drilling also can be used for adaptive stack drilling, cutting returns, and countersinking.

However, orbital drilled holes typically experience an inferior fatigue life (e.g., a fatigue knockdown) when compared to reamed holes. Such a fatigue knockdown is due to a reaming process inducing beneficial residual stresses in the wall of the hole that improve fatigue life, whereas an orbital drilling process cuts cleanly and leaves the machined surface in a neutral state of stress. However, such reaming processes create burrs in the machined surface that do not allow for one up assembly. Further, conventional drilling processes are more time consuming and labor intensive. As such, methods and systems for orbital drilling that induces residual stresses in the wall of the hole may be desirable.

Referring now to the figures, <FIG> illustrates an example cutting tool, according to one embodiment. In particular, <FIG> illustrates a three-dimensional view of the cutting tool <NUM>. The cutting tool <NUM> includes a body <NUM> having a leading end <NUM> including a first portion <NUM>, an attachment end <NUM> configured to couple the cutting tool <NUM> to an orbital drilling system, and a second portion <NUM> positioned between the first portion <NUM> and the attachment end <NUM>. As shown in <FIG>, the second portion <NUM> may extend an entire length from the first portion <NUM> to the attachment end <NUM>. The attachment end <NUM> may be substantially smooth so as to fit in an orbital drill chuck. The cutting tool <NUM> may further include one or more openings <NUM> extending through the cutting tool to allow heat to dissipate or lubrication to reach the cutting surface. The first portion <NUM> has a first diameter and a first radial rake angle. The second portion <NUM> is adjacent to the first portion <NUM> and has a second diameter that differs from the first diameter of the first portion <NUM>. The second portion <NUM> further has a second radial rake angle that differs from the first radial rake angle of the first portion <NUM>. In particular, the second diameter of the second portion <NUM> is larger than the first diameter of the first portion <NUM>.

<FIG> is an illustration of a single tooth face <NUM>. The tooth face <NUM> has been isolated and its angles and geometry have been exaggerated for the purposes of explanation and clarity. <FIG> does not represent the geometry of the current invention. Rather, <FIG> is intended to illustrate a positive radial rake angle that would be seen in a cross section of the first portion <NUM>. As shown in <FIG>, the first portion <NUM> has a first radial rake angle <NUM>, and a direction of rotation <NUM>. The radial rake angle <NUM> of the cutting tool <NUM> is the angle between the tooth face <NUM> and a radial line <NUM> passing through the cutting edge in a plane perpendicular to the cutting axis. In <FIG>, the first portion <NUM> has a positive radial rake angle <NUM>. The positive radial rake angle <NUM> of the first portion <NUM> initially removes the majority of the material to form a hole in the workpiece having a sidewall while generating minimal heat.

<FIG> is an illustration of a single tooth face <NUM>. The tooth face <NUM> has been isolated and its angles and geometry have been exaggerated for the purposes of explanation and clarity. <FIG> does not represent the geometry of the current invention. Rather, <FIG> is intended to illustrate a negative radial rake angle that would be seen in a cross section of the second portion <NUM>. As shown in <FIG>, the second portion <NUM> has a second radial rake angle <NUM>, and a direction of rotation <NUM>. As previously described, the radial rake angle <NUM> of the cutting tool <NUM> is the angle between the tooth face <NUM> and a radial line <NUM> passing through the cutting edge in a plane perpendicular to the cutting axis. In <FIG>, the second portion <NUM> has a negative radial rake angle <NUM>. The negative radial rake angle <NUM> of the second portion <NUM> removes a small amount of additional material from the sidewall of the hole to thereby impart residual stresses in the sidewall. These residual stresses improve the fatigue like of such orbital drilled holes and are particularly beneficial in aluminum structures.

A positive radial rake angle <NUM> of <NUM> degrees and a negative radial rake angle of negative <NUM> degrees has been shown to impart beneficial residual stresses while prolonging tool life.

<FIG> depicts another cross section of the second portion <NUM> of the cutting tool <NUM>. As shown in <FIG>, the cutting tool <NUM> includes at least one hollow opening (although two are depicted, the tool may function with one or none) <NUM>. Hollow openings <NUM> may extend partly or entirely through the length of the cutting tool <NUM>. Where hollow openings <NUM> extend entirely through the length of the cutting tool <NUM>, they may be in fluid communication with a lubricant or water source (not shown) configured to provide lubrication or cooling water to the cutting surface. Alternatively, the hollow openings may be exposed to ambient conditions to allow heat from the cutting surface to dissipate to the air.

<FIG> is a close-up view of the first portion <NUM> of the cutting tool <NUM> in operation. The positive radial rake angle <NUM> of the first portion <NUM> is tilted away from the cut direction <NUM> such that the cut chip <NUM> is lifted from the workpiece <NUM>. Similarly, <FIG> depicts a close-up view of the second portion <NUM> of the cutting tool <NUM>. The negative radial rake angle <NUM> of the second portion <NUM> is tilted towards the cut direction <NUM> such that the cut chip <NUM> is forced down into the workpiece <NUM>.

The first portion <NUM> of the cutting tool <NUM> may have a length that is substantially smaller than the length of the second portion <NUM>. For example, the ratio of the length of the first portion <NUM> to the length of the second portion may be <NUM>:<NUM>, <NUM>:<NUM>, or <NUM>:<NUM>, as examples. In one further example, the first portion <NUM> may have a length that approximately corresponds with a thickness of a workpiece through which the orbital drilling system <NUM> will drill. For example, if the cutting tool is configured to drill holes in a material that is approximately <NUM>,<NUM> (<NUM> inches) thick, the first portion <NUM> may have a length that is approximately <NUM>,<NUM> (<NUM> inches).

The first portion <NUM> and the second portion <NUM> may be made from the same material, such as carbide, or high speed steel as examples. In another example, the first portion <NUM> may be made from a first material, while the second portion <NUM> may be made from a second material. Further, although the radial rake angle for the first portion <NUM> and the second portion <NUM> are different, other attributes of the cutting tool <NUM> may be the same in the first portion <NUM> and the second portion <NUM>. For example, the axial rake angle, the helical angle, and other characteristics of the flutes and cutting edges of the cutting tool <NUM> may be the same in the first portion <NUM> and the second portion <NUM>.

<FIG> is a block diagram of an example orbital drilling system <NUM>, according to one embodiment. The orbital drilling system <NUM> includes a control unit <NUM> coupled to a power supply <NUM> and sensor(s) <NUM>. The control unit <NUM> is further coupled to an automated drilling machine <NUM> which, in turn, is coupled to a motor <NUM> that is coupled to a cutting tool <NUM>. The control unit <NUM> may be independently coupled to both the automated drilling machine <NUM> and the motor <NUM>. The automated drilling machine <NUM> may be configured to receive coordinate data from the control unit <NUM> describing the desired location of the hole to be cut. The automated drilling machine <NUM> is configured to move the cutting tool <NUM> to the desired hole location. The motor <NUM> is configured to move the cutting tool <NUM> in an orbital pattern to form a hole in a workpiece. The cutting tool <NUM> further includes a body <NUM>, and the body includes a leading end <NUM> and an attachment end <NUM>. The attachment end <NUM> is configured to couple the motor <NUM> to the cutting tool <NUM>. In particular, the attachment end <NUM> is substantially smooth so as to fit in an orbital drill chuck, for example. The leading end <NUM> includes a first portion <NUM> of the body <NUM>. Further, a second portion <NUM> of the body <NUM> is positioned between the first portion <NUM> and the attachment end <NUM>. In particular, the second portion <NUM> may extend an entire length of the body <NUM> from the first portion <NUM> to the attachment end <NUM>. The orbital drilling system <NUM> may further include a vacuum system <NUM> coupled to the cutting tool <NUM> to remove debris from drilling, which eliminates disassembly and reassembly for cleaning. The orbital drilling system <NUM> may also include a lubrication system <NUM> coupled to the cutting tool <NUM> so as to provide lubrication to the cutting surface.

In one example, the first portion <NUM> and the second portion <NUM> may be made from the same material, such as carbide, or high speed steel as examples. In another example, the first portion <NUM> may be made from a first material, while the second portion <NUM> may be made from a second material. Further, although the radial rake angle for the first portion <NUM> and the second portion <NUM> are different, other attributes of the cutting tool <NUM> may be the same in the first portion <NUM> and the second portion <NUM>. For example, the axial rake angle, the helical angle, and other characteristics of the flutes and cutting edges of the cutting tool <NUM> may be the same in the first portion <NUM> and the second portion <NUM>.

The control unit <NUM> may be configured to operate the cutting tool <NUM>, and to provide power from the power supply <NUM> to the motor <NUM> to do so. The control unit <NUM> may also be configured to operate the automated drilling machine <NUM> by providing power from the power supply <NUM> and coordinate data from the sensors <NUM>. The control unit <NUM> may receive outputs from the sensors <NUM> to determine when to initiate operation of the cutting tool <NUM>. The sensors <NUM> may include one or more gyroscopes, one or more accelerometers, one or more magnetometers, one or more light sensors, and/or one or more infrared sensors. The sensors <NUM> may more generally include sensors for detecting a location of a workpiece, and a position of the cutting tool <NUM> with respect to the workpiece.

In operation, the leading end <NUM> of the cutting tool <NUM> first contacts the workpiece. As such, the positive radial rake angle of the first portion <NUM> initially removes the majority of the material to form a hole in the workpiece while generating minimal heat. As the cutting tool <NUM> moves axially through the workpiece, the negative radial rake angle of the second portion <NUM> removes a small layer of material from a sidewall of the hole to thereby impart residual stresses in the sidewall. To control excessive heat buildup in the sidewall due to the stresses induced by the negative radial rake angle, the difference in the first diameter and the second diameter can be altered such that the second portion <NUM> only removes a very small width of material. Further, by removing the bulk of material with the first portion <NUM> having a positive radial rake angle, and only a small amount of material with the second portion <NUM> having a negative radial rake angle, excessive heat is not imparted on the cutting tool <NUM> and/or workpiece. As discussed above, the additional residual stresses in the sidewall of the hole imparted by the second portion <NUM> may help improve the fatigue life of such orbital drilled holes, particularly in aluminum workpieces.

<FIG> illustrates a schematic drawing of an example computing device <NUM>. The computing device <NUM> in <FIG> may represent the control unit <NUM> shown in <FIG>. In some examples, some components illustrated in <FIG> may be distributed across multiple computing devices. However, for the sake of example, the components are shown and described as part of one example computing device <NUM>. The computing device <NUM> may be implemented as, for example but without limitation, a part of an orbital drilling system, or other implementation.

The computing device <NUM> may include an interface <NUM>, a wireless communication component <NUM>, sensor(s) <NUM>, data storage <NUM>, and a processor <NUM>. Components illustrated in <FIG> may be linked together by a communication link <NUM>. The computing device <NUM> may also include hardware to enable communication within the computing device <NUM> and between the computing device <NUM> and another computing device (not shown), such as a server entity. The hardware may include transmitters, receivers, and antennas, for example.

The interface <NUM> may be configured to allow the computing device <NUM> to communicate with another computing device (not shown), such as a server or land-based device. Thus, the interface <NUM> may be configured to receive input data from one or more computing devices, and may also be configured to send output data to the one or more computing devices. In some examples, the interface <NUM> may also maintain and manage records of data received and sent by the computing device <NUM>. The interface <NUM> may also include a receiver and transmitter to receive and send data.

The wireless communication component <NUM> may be a communication interface that is configured to facilitate wireless data communication for the computing device <NUM> according to one or more wireless communication standards. For example, the wireless communication component <NUM> may include a Wi-Fi communication component, or a cellular communication component. Other examples are also possible, such as proprietary wireless communication devices.

The sensor(s) <NUM> may include one or more sensors, or may represent one or more sensors included within the computing device <NUM>. Example sensors may include one or more gyroscopes, one or more accelerometers, one or more magnetometers, one or more light sensors, and/or one or more infrared sensors, for example. The sensors <NUM> may more generally include sensors for detecting a location of a workpiece, and a position of the cutting tool <NUM> with respect to the workpiece.

The processor <NUM> may be implemented, or realized, with a general purpose processor, a content addressable memory, a digital signal processor, an application specific integrated circuit, a field programmable gate array, any suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein.

The data storage <NUM> may contain program logic <NUM> and reference data <NUM>. Reference data <NUM> is configured to store, maintain, and provide data as needed to support the functionality of the system. For example, the reference data <NUM> may store orbital drilling command signals, or other data. Program logic <NUM>, in turn, may then comprise machine language instructions or the like that are executable by the processing unit <NUM> to carry out various functions described herein.

In practical embodiments, the data storage <NUM> may comprise, for example but without limitation, a non-volatile storage device (non-volatile semiconductor memory, hard disk device, optical disk device, and the like), a random access storage device (for example, SRAM, DRAM), or any other form of storage medium known in the art.

The data storage <NUM> may be coupled to the processor <NUM> and configured to store, for example but without limitation, a database, and the like. Additionally, the data storage <NUM> may represent a dynamically updating database containing a table for updating the database, and the like. The data storage <NUM> may be coupled to the processor <NUM> such that the processor <NUM> can read information from and write information to the data storage <NUM>. For example, the processor <NUM> may access the data storage <NUM> to access a cutting tool rotation speed, or other data.

As an example, the processor <NUM> and data storage <NUM> may reside in respective application specific integrated circuits (ASICs). The data storage <NUM> may also be integrated into the processor <NUM>. In an embodiment, the data storage <NUM> may comprise a cache memory for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor <NUM>.

<FIG> shows a flowchart of an example method <NUM> for forming a hole through at least one layer of a material, according to one embodiment. Method <NUM> shown in <FIG> presents an embodiment of a method that, for example, could be used with the orbital drilling system shown in <FIG>, for example, and may be performed by a computing device (or components of a computing device, such as those shown in <FIG>), or may be performed by an operator. Thus, example devices or systems may be used or configured to perform logical functions presented in <FIG>. In some instances, components of the devices and/or systems may be configured to perform the functions such that the components are actually configured and structured (with hardware and/or software) to enable such performance. In other examples, components of the devices and/or systems may be arranged to be adapted to, capable of, or suited for performing the functions. Method <NUM> may include one or more operations, functions, or actions as illustrated by one or more of blocks <NUM>-<NUM>. Although the blocks are illustrated in a sequential order, these blocks may also be performed in parallel, and/or in a different order to those described herein. Also, the various blocks may be combined into fewer blocks, divided into additional blocks, and/or removed based upon the desired implementation.

It should be understood that for this and other processes and methods disclosed herein, flowcharts show functionality and operation of one possible implementation of present examples. In this regard, each block may represent a module, a segment, or a portion of program code, which includes one or more instructions executable by a processor for implementing specific logical functions or steps in the process. The program code may be stored on any type of computer readable medium or data storage, for example, such as a storage device including a disk or hard drive. The computer readable medium may include non-transitory computer readable medium or memory, for example, such as computer-readable media that stores data for short periods of time like register memory, processor cache and Random Access Memory (RAM). The computer readable medium may also include non-transitory media, such as secondary or persistent long term storage, like read only memory (ROM), optical or magnetic disks, compact-disc read only memory (CD-ROM), for example. The computer readable media may also be any other volatile or non-volatile storage systems. The computer readable medium may be considered a tangible computer readable storage medium, for example.

In addition, each block in <FIG> may represent circuitry that is wired to perform the specific logical functions in the process. Alternative implementations are included within the scope of the example embodiments of the present disclosure in which functions may be executed out of order from that shown or discussed, including substantially concurrent or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art.

At block <NUM>, the method <NUM> includes removing a portion of the material from the at least one layer using a first portion of a cutting tool to form a hole having a sidewall, wherein the first portion has a first diameter and a first radial rake angle. At block <NUM>, the method <NUM> includes removing additional material from the sidewall using a second portion of the cutting tool, wherein the second portion has a second diameter and a second radial rake angle, wherein the second diameter differs from the first diameter, and wherein the second radial rake angle differs from the first radial rake angle, the first radial rake angle being <NUM> degrees and the second radial rake angle being negative <NUM> degrees.

As discussed above, the second diameter may be larger than the first diameter. The first radial rake angle is a positive radial rake angle of <NUM> degrees, and the second radial rake angle is a negative radial rake angle of negative <NUM> degrees.

As such, the positive radial rake angle of the first portion initially removes the majority of the material to form a hole in the workpiece having a sidewall while generating minimal heat. As the cutting tool moves axially through the workpiece, the negative radial rake angle of the second portion removes the additional material from the sidewall of the hole to thereby impart residual stresses in the sidewall. The additional residual stresses in the sidewall of the hole may help improve the fatigue life of such orbital drilled holes.

The particular arrangements shown in the Figures should not be viewed as limiting. It should be understood that other examples may include more or less of each element shown in a given Figure. Further, some of the illustrated elements may be combined or omitted. Yet further, an example may include elements that are not illustrated in the Figures.

Additionally, while various aspects and examples have been disclosed herein, other aspects and examples will be apparent to those skilled in the art. The various aspects and examples disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims. Other embodiments may be utilized, and other changes may be made, without departing from the scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are contemplated herein.

Hence, there is provided a cutting tool according to claim <NUM>.

Advantageously the second diameter of the cutting tool is larger than the first diameter. As another advantage the second radial rake angle of the cutting tool imparts a residual stress on a sidewall of a hole formed by the cutting tool. As yet another advantage the body of the cutting tool includes a leading end including the first portion, and wherein the body includes an attachment end opposite the leading end, and wherein the attachment end is configured to couple the cutting tool to an orbital drilling system. As yet another advantage, the body of the cutting tool includes at least one hollow opening through the length of the body.

Further, there is provided an orbital drilling system according to claim <NUM>.

Advantageously, the orbital drilling system, further comprises:
a plurality of sensors configured to detect position of the cutting tool with respect to the workpiece. As another advantage the orbital drilling system, further comprises: a vacuum system coupled to the cutting tool to remove debris from drilling. As another advantage the orbital drilling system, further comprises: a lubrication system coupled to the cutting tool to provide lubrication to the cutting surface.

Advantageously the second diameter of the cutting tool of the orbital drilling system is larger than the first diameter of the orbital drilling system. As another advantage, the second radial rake of the cutting tool of the orbital drilling system imparts a residual stress on a sidewall of a hole formed by the cutting tool. Preferably, the body of the cutting tool of the orbital drilling system includes a leading end including the first portion, wherein the body includes an attachment end opposite the leading end, and wherein the attachment end is configured to couple the cutting tool to the motor. Advantageously the body of the cutting tool of the orbital drilling system includes at least one hollow opening through the length of the body.

Claim 1:
A cutting tool (<NUM>) comprising:
a body (<NUM>);
a first portion (<NUM>) of the body (<NUM>) having a first diameter and a first radial rake angle (<NUM>); and
a second portion (<NUM>) of the body (<NUM>) adjacent the first portion (<NUM>), the second portion (<NUM>) having a second diameter and a second radial rake angle (<NUM>), wherein the second diameter differs from the first diameter, and wherein the second radial rake angle (<NUM>) differs from the first radial rake angle (<NUM>),
wherein the first radial rake angle (<NUM>) is a positive radial rake angle, and the second radial rake angle (<NUM>) is a negative radial rake angle, and
characterised in that the first radial rake angle (<NUM>) is <NUM> degrees, and wherein the second radial rake angle (<NUM>) is negative <NUM> degrees.