Patent Description:
The present invention relates to a drilling system according to the preamble of claim <NUM>, and further to deep hole drilling systems, which produce holes with a large depth to diameter ratio in a highly accurate and effective manner. Such a drilling system is known from <CIT>.

Certain deep hole drilling systems such as gun drills, single tube drilling systems, and double tube drilling systems are known in the art. These deep hole drilling systems may be used for drilling holes with a large depth to diameter ratio.

Solid carbide tooling is disadvantageous due to the need to regrind the cutting edges when worn, requiring removal of the tool from the drilling machine. Other problems with deep hole drilling tools include instability during drilling and at breakout. Tools having replaceable cutting heads have also been developed, which may use indexable cutting inserts. For example, there have been developed a single tube drilling system, or STS, used to drill holes having large depth to diameter ratios with improved penetration rates, hole size accuracy, and straightness as compared to gun drills. At the same time, such systems have various disadvantages, due to a single effective cutting edge, use of one or more wear pads which tend to bear on the sides of the formed hole during cutting with significant force. The wear pad tend to cause hardening of the hole and embrittlement of the material. The wear pads on the tool body are used in an attempt to provide stability to the front of the drill by making contact with the inside wall of the hole just previously drilled. The use of a wear pad on the opposing side of a major diameter cutting insert has to be set at a diameter under the insert. This causes the tool to drill under or over size due to the imbalance of cutting forces and the inability to precisely balance these forces.

Other solid drilling tools are available for drilling of holes, but have deficiencies when attempting to drill large diameter and/or deep holes. Such tools have difficulty in such applications, due to torque loading and thrust requirements. It would be desirable to provide a drilling tool that can achieve more efficient cutting in such applications, to achieve higher speed with lighter feed rates.

Problems with past tool designs also include issues such as chips remaining in the hole between the body diameter and the inside of the hole or inability to effectively evacuate chips during drilling. Such occurrence causes significant problems in efficient and precise drilling, and adversely affect cut quality and cutting tool life.

For many applications, there is a need for tooling that can more effectively produce holes with a large diameter or large depth to diameter ratio, with high accuracy and in a cost effective manner. It would therefore be desirable to have a tool that provides stability and keeps the drilling on center. It would also be desirable to provide tooling that allows simple and flexible set-ups and modularity to provide adjustment which allows the tool to more effectively drill large depth to diameter ratio holes with high accuracy in various applications and materials.

The invention is therefore directed to a drill system according to claim <NUM> comprising a generally cylindrical holder body member. A replaceable cutting head is mountable to the front end of the holder body. A central cutting system, such as cutting insert, is attached to the cutting head, and has first and second cutting edges extending from the rotational axis of the cutting head. Additionally, first and second side cutting inserts are mountable to the cutting head, each having a cutting edge extending from adjacent the central cutting member to cut the major diameter of a hole.

Other aspects of the invention will be apparent to those of skill in the art in view of the following written description and drawings relating to examples of the invention.

Referring now to <FIG>, an example of a drilling system according to the invention is shown. As shown in <FIG>, the drilling system <NUM> includes a drilling head <NUM> and an holder body or shank <NUM>. The drilling system <NUM> of this example utilizes a through tool coolant system to be described hereafter, to provide coolant to the area of drilling head <NUM>, and allows coolant to flow around the drilling head <NUM> and back through the flush channels <NUM>, thereby efficiently flushing metal chips produced during drilling out of the hole. The drilling system may be configured to provide a cutting fluid delivery system to provide a desired volume of cutting fluid at desired pressures for a particular application.

In this example, the drilling head <NUM> is designed to support a plurality of cutting inserts. The drilling head <NUM> of this example includes a central insert <NUM> supported in the drilling head <NUM> and side cutting inserts <NUM> and <NUM>, positioned in side insert pockets <NUM> formed in the drilling head <NUM>. A central guide post <NUM> (see <FIG> for example) at the bottom center of the drilling head <NUM> is provided to facilitate positioning of the modular drilling head <NUM> onto the body <NUM>. Flute areas <NUM> are provided adjacent the central insert support <NUM> for evacuation of machined chips from the central cutting insert <NUM>. As seen in this example, a central cutting insert <NUM> may be provided as a spade type of drilling insert having an approximately flat polygonal shape having first and second faces and first and second side edges. The cutting insert may comprise one or more mounting apertures through the first and second faces, and fastened to ears or supports <NUM> formed on the drilling head <NUM>. The cutting insert <NUM> may further comprise a self-centering point <NUM>, cutting edges <NUM> extending from the point <NUM> and optionally one or more chip breakers. The use of one or more chip breakers may facilitate controlling the width of chips produced by the cutting insert <NUM>. Controlling the chip width facilitates effective evacuation of chips through the flutes <NUM> for example. In some applications, chip breakers may not be required, for example with use in cutting cast iron or carbon fibers. The cutting edges <NUM> are positioned at the leading edges as the insert <NUM> rotates. The cutting insert <NUM> may be an approximately symmetrical shape with the axis of rotation passing through the self-centering point <NUM>. In a particular example, the insert <NUM> may further include a central cutting web <NUM> with web cutting edges adjacent the point <NUM>. The use of one or more web cutting edges in conjunction with cutting web <NUM> adjacent the point <NUM> facilitates enabling the material at the tip of the cutting insert <NUM> to shear and form a manageable chip. The web cutting edges may be radiused or notched with flat surfaces to facilitate use with different applications, or may be a v-notch configuration such as shown in <CIT> for example. The provision of a cutting web <NUM> may enable chip formation at the drill point and reduce extrusion due to the shearing ability of the cutting web. Further, the cutting web <NUM> may enable the drill cutting insert <NUM> to start the hole on-center and to retain its straightness. Further, at least one cutting lip may be positioned adjacent one or more cutting edges <NUM>. The cutting lip may include geometry capable of producing curled metal chips for evacuating from the hole. The central cutting insert <NUM> may be the T-A or Gen2 T-A product produced by Allied Machine & Engineering Corporation, of Dover, OH for example, or a different type of central cutting member may be used, such as one or more indexable inserts, twist drills or other cutting members for machining of a metal or other workpiece.

In this example, there may also be provided first and second side cutting inserts <NUM> and <NUM>, for cutting the outside diameter of the hole. The side inserts <NUM> and <NUM> are mounted in pockets <NUM> formed in the drilling head <NUM>. The side inserts <NUM> and <NUM> may be indexable to provide multiple cutting edges that can be successively used after wear of a cutting edge, or could be non-indexable cutting inserts. In this example, the center insert <NUM> is mounted to drilling head <NUM> via mounting screws that engage the mounting ears <NUM>. The drilling head <NUM> is mounted to the body <NUM> and fastened by one or more screws or the like, that draws the modular drilling head <NUM> onto the body <NUM> and forces the modular head against extensions or ears <NUM> formed on the body <NUM>. The coupling of the inserts and modular head may be performed by any suitable fastening system.

In association with this example, the inserts <NUM> and <NUM> are designed with cutting margins <NUM> to facilitate precise machining. In this example, the inserts <NUM> and <NUM> are rhomboid shaped, but other shapes may be used. The insert design provides margined inserts <NUM> and <NUM> at the major drilling diameter to provide stability on entry, during the drilling cut cycle, and during the breakout on through hole applications. The use of the drilling system is not limited to through hole applications, and can also be used on blind hole applications or other hole applications. As indexable inserts in this example, the inserts <NUM> and <NUM> include cutting margins <NUM> on both edges. In this example, the double margin inserts <NUM> and <NUM>, with cutting margins <NUM> located at the major drilling diameter, are rotated out from the center insert <NUM> margined OD plane. The angle between the cutting plane of the side cutting inserts <NUM> and <NUM> and the cutting plane of the center cutting member <NUM> may be between <NUM>° - <NUM>°. The rotation of the cutting plane of the side inserts <NUM> and <NUM> away from the cutting plane of the center cutting member <NUM> also breaks up the harmonics of the system, reducing drill vibration and tool chatter. This arrangement provides the drilling system with four points of margined support in the drilling operation which increases the overall stability. This overall stability control will produce a truer hole and also aid in the surface finish in the cut with the four points of margin contact. This maintains the drill on centerline as the tool does not have the increased opportunity to move radially off the centerline of the hole during the drilling cycle. Alternatively, the cutting plane of the side inserts <NUM> and <NUM> do not have to be rotated relative to the cutting plane of the center insert <NUM>. The ability to index the side inserts <NUM> and <NUM> to reveal a new cutting edge and provide the same margin support as noted above adds additional value due to the increased overall life that the inserts <NUM> and <NUM> will have. Further, in operation, when the cutting edges on inserts have reached their expected life, the cutting inserts can be removed from the drilling head <NUM> and new cutting inserts easily installed and the drilling process continued.

In this example, the holder body <NUM> may comprise a generally circular shape having a first end, or shank end <NUM>, and a second end <NUM>. Evacuation flutes or channels <NUM> are formed on opposing sides of body <NUM>, for passing chips and cutting fluid from the drilled hole. The shank end <NUM> of the holder body <NUM> may be coupled to a drilling machine in any suitable manner. There may also be provided in this example, drill guide pads <NUM> set under the major drilling diameter adjacent the side inserts <NUM> and <NUM> for clearance to avoid creating a seizure of the tool or marring of the drilling surface in the cut. Further guide pads <NUM> are positioned at about ninety degrees from pads <NUM> and adjacent the flutes <NUM>. The first and second wear surfaces provided by pads <NUM> and <NUM> in this example are offset axially. The guide pads <NUM> and <NUM> give support to the tool during the drilling cycle. The pads may be screwed into position or otherwise suitably attached. The pads may be formed of a carbide material or ground carbide material such as titanium carbide, a tungsten carbide, aluminum bronze, high speed steel, hard chroming or other suitable wear material. The pads serve as bearing areas for the holder body <NUM> to support the tool in an interrupted cut situations for example, (i.e. drilling through a cross hole or an uneven breakout), as well as tending to force the tool to run straight if the tool begins to lead off during the cut. Alternative wear surfaces may be used. Coolant is provided through holes <NUM> formed in the body <NUM>, which directs coolant to the cutting edges of the cutting inserts <NUM> and <NUM>. Coolant may also be provided to holes <NUM> to the cutting surfaces of the insert <NUM>, and lubricate the area where guide pads <NUM> and <NUM> are positioned along with holes <NUM>. The clearance on the back side of the inserts allows coolant to flow up and over the inserts, simultaneously forcing the chips into the flutes or channels <NUM>, and out of the hole.

This example of the invention also provides a modular drilling head <NUM> that allows the replacement of drilling head <NUM> in an easy manner in the case of damage. The system <NUM> of the invention allows a user to easily rebuild the tool in the event of minor tool failures. The replaceable drilling head <NUM> that serves as an insert holder allows rebuilding of the system without replacing costly holder bodies <NUM>. Also, as seen in <FIG>, the center insert <NUM> and/or two side inserts <NUM> and <NUM> may be adjusted. As seen in <FIG>, adjustability of the center insert <NUM> may be provided by two set screws <NUM> positioned under the slot for positioning of the insert <NUM>. The set screws <NUM> allow pushing the pin (not shown) of the center insert <NUM> that locates in hole <NUM> radially in the same plane of the insert margins. This gives the user the ability to negate the buildup of manufacturing tolerances and ensure that the center insert <NUM> is running centrally by taking out the TIR. When center insert <NUM> is running in near-perfect on center condition, the cutting forces are more evenly balanced and the system drills straighter. This also helps keep the system on center through the entire drilling process as opposed to starting out with some TIR and not being able to correct this. When the tool starts the drilling process in an out of center condition it will have a greater probability to run-out, and over a long length of cut this increases exponentially. The adjustment of the center insert <NUM> may allow the user to compensate for the stack up of manufacturing tolerances in the connection to the components of the system, to facilitate proper precise drilling.

Similarly, with reference to <FIG>, the position of the side inserts <NUM> and <NUM> can also be adjusted. The second portion of adjustability is designed for the major diameter cutting of the double effective cutting double margin inserts <NUM> and <NUM>. Two additional set screws <NUM> may be provided with the drilling head <NUM>, to provide the ability to push on the inside wall clearance angle of the inserts <NUM> and <NUM>, thereby moving one or both of the inserts <NUM> and <NUM> axially to adjust the major diameter of each insert <NUM> and <NUM>. This adjustability allows the user to overcome the buildup of manufacturing tolerances so that the major cutting diameter could be set to a near perfect condition for both inserts <NUM> and <NUM>. Setting both of the inserts <NUM> and <NUM> as close as possible to the major cutting diameter desired ensures that the cutting forces will be well balanced, allowing for more even wear of the inserts <NUM> and <NUM>, as well as a more precise drilled hole size. The design being setup as a double effective cutting tool also allows for a significant increase in allowable penetration rate versus a single effective tool.

The disclosed drilling system <NUM> also provides additional flexibility to meet objectives for different applications. For example, the substrate, coating, and geometry options may allow for the system <NUM> to function in applications where prior art drills fail. The substrate material of the cutting inserts <NUM> and/or <NUM> and <NUM> may be changed to accommodate different types of applications. Also, different coatings may be usable in association with the inserts <NUM> and/or <NUM> and <NUM>. For example, a diamond film coating may be used on the cutting edges and clearance surfaces of inserts <NUM> and/or <NUM> and <NUM> to minimize flank wear growth. An example of these types of films include carbon vapor deposition (CVD) polycrystalline diamond film. Diamond film coatings may be helpful when cutting non-metallic abrasive materials for example. Other coating materials, such as titanium aluminum nitride or other suitable materials, may be used. The inserts <NUM> or <NUM> and <NUM> may be coated by known suitable methods, with a desired coating based upon a particular application for the system <NUM>. The use of inserts <NUM> and <NUM> and <NUM> also allows the cutting geometry to be formed for various applications, with various modifications in cutting geometry possible to enhance the cutting performance for different applications or materials. For example, different cutting geometries may include, but are not limited to, the cutting lip geometry having a positive rake angle, the cutting web having a positive rake angle, the insert <NUM> having a self-centering point, and/or providing a desired chip breaking configuration in association with the cutting edges. Positive cutting lip geometry produces a tightly curled chip that is easy to evacuate through the tool, with the compact size of the chip resulting from the predetermined lip position, size and configuration. Many modifications can be made to the lip configuration to enhance the development of chip formation for example.

A second significant improvement with the disclosed drilling system is a reduction in cost per hole. This may be realized in several different ways. When the tool is worn out or damaged, the modular design of the drilling head <NUM> in conjunction with a body <NUM> avoids the need to replace the head and/or body. This can be costly, especially as the hole diameter increases. With the presently disclosed invention, an operator may replace the worn or damaged cutting inserts <NUM> and <NUM> and <NUM> easily, without affecting set up of the system. The drilling system thus provides the ability to quickly and efficiently change the cutting edges when they become worn. The cost of the holder body <NUM> may be amortized over multiple cutting insert changes reducing the total tool cost.

The cost per hole can also be calculated based on an increased penetration rate. The presently disclosed drilling system includes two effective cutting edges from the center to the OD. This design can offer a significant performance improvement or advantage over a single effective cutting tool. With two effective cutting edges, the system may allow doubling of the feed rate of a comparable single cutting edge design. This increased penetration rate reduces the time in the cut freeing up machine time. The arrangement according to the examples of the present invention provides various improvements and overcomes problems associated with prior systems. For example, the arrangement does not result in work hardening of the material adjacent the hole, as no significant forces are imposed on the sides of the formed hole. The drill guide pads are not bearing on the sides of the hole with significant force, but instead are used to facilitate guiding the tool during cutting. The cutting geometry provided by the center insert <NUM> and side inserts <NUM> and <NUM> may comprise an included angle such as in the example of the drilling head <NUM> in <FIG>, so that radial loads imposed by the system are minimized, and heat generation is also minimized, such that no embrittlement of the machined material occurs. The double effective tool is capable of running at higher penetration rates, while having modular capability. This double effective design in conjunction with both of the major diameter cutting inserts having adjustability ensure that the margins of the tool run concentric and on size, allowing the system to drill straighter, provide a better surface finish, and increase the overall stability of the tool during the drilling process. The drilling system <NUM> in accordance with the present invention may include a variety of features and attributes to promote stability and chip removal, and maximize the precision of the drilling operation while increasing tool life.

Claim 1:
A drilling system comprising a generally cylindrical body member (<NUM>), a replaceable cutting head (<NUM>) mounted to the front end of the body member having a central cutting system (<NUM>) with first and second cutting edges (<NUM>) extending from the rotational axis of the cutting head (<NUM>), and first and second side cutting inserts (<NUM>,<NUM>) disposed outwardly from the central cutting system (<NUM>), the side cutting inserts (<NUM>,<NUM>) each having a cutting edge extending from adjacent the first and second cutting edges (<NUM>) of the central cutting system to cut the major diameter hole, wherein the side cutting inserts (<NUM>,<NUM>) are indexable and have first and second cutting edges on opposing sides of each side cutting insert (<NUM>,<NUM>), and where the first and second side cutting inserts (<NUM>,<NUM>) include edges that extend between the first and second cutting edges on opposing sides of each side cutting insert (<NUM>,<NUM>), characterised in that an edge extending between the first and second cutting edges of each side cutting insert (<NUM>, <NUM>) forms a margin (<NUM>) at the major drilling diameter which engages a hole during drilling.