Patent Description:
In deep hole drilling systems, modern machine tools have led to the need for tooling that can effectively produce holes with a large depth to diameter ratio.

For making large diameter deep holes, the tooling that has been used does not account for using modern machine tools with less available horsepower. The machine tools that are found in use today generally have less available horsepower and can only reach that available peak horsepower at high spindle speeds. Conventional deep hole drilling may utilize double effective cutting geometry where both edges share an equal amount of the cutting load. This type of geometry allows for a drill to establish a centerline and act as a guide for the rest of the drill body following it. This enables longer drill bodies to drill straighter holes without leading off of centerline. In order to achieve chip formation in a way that chip evacuation at depth is manageable, these types of drill would need to be run at heavy feed rates in order to segment the chips. Furthermore, the drill would require being rotated at a relatively low spindle speed to manage the heat at the OD of the tool.

Another style of deep hole drilling that may be utilized is single effective gun drills or ejector head drilling tools. These types of tools are more suited to higher depth to diameter ratios and often require special machines and set-ups to be effective. These types of tools may also utilize a bearing surface on the tool body to attempt to provide stability to the front of the drill by making contact with the inside wall of the hole just previously drilled. This technology is widely used throughout the industry to attempt to provide stability to longer drills or to attempt to keep them drilling on center. It would be desirable to provide tooling that allows simple and flexible set-ups and use of standard machine tools.

Attempts to use a large spade blade to drill deep holes have also been pursued. However, these tools run at lower speeds and higher feed rates. Lower speeds mean that the machine is operating at the lower portion of the machines power curve. Higher feed rates require more thrust which may not be available on modern drilling machines. Indexable Carbide (IC) drills may be used to drill holes at high spindle speeds and lesser feeds. An IC drill will consume less thrust and will run at the higher end of the power curve relative to a spade drill of the same diameter. However at depths greater than 4xDiameter, IC drills lack stability and tend to lead off center which produces a hole that may not meet straightness requirements. Indexable inserts are available in various shapes and have the ability to be rotated (or indexed) to a fresh cutting edge when worn, and eventually replaced. This offers the ability to reuse the tool body any number of times by replacing the worn inserts. The drill body includes pockets to position the inserts by means of a screw or mechanical clamping mechanism. The position of the pocket on the cutting end of the drill body determines the size of the hole to be drilled. These types of drills are considered single flute effective, meaning that the inserts overlap. One insert cuts a portion of the diameter from the major diameter in towards the centerline and the other inserts cut the remaining portion from the centerline out to the point where it overlaps with the other insert.

<CIT>discloses a drilling system according to the preamble of claim <NUM>.

<CIT> discloses a rotatable tool for chip removing machining, including a basic body having front and rear ends between which a first center axis extends, with which an envelope surface is concentric and around which the basic body is rotatable; and a loose top that includes front and rear ends between which a second center axis extends with which an envelope surface is concentric. The front end of the basic body includes a jaw which is delimited by two torque-transferring drivers and an intermediate bottom in which a rear coupling part of the loose top is receivable, and a center hole that mouths in the intermediate bottom. The center hole has a hole wall which extends axially inside the basic body and in which a threaded hole being concentric with a third center axis mouths for a screw to co-operate with a centric pin which protrudes axially rearward from the coupling part. The centric pin is insertable into the center hole, and the threaded hole is accessible from the outside of the basic body. The coupling part of the loose top includes a pair of axial contact surfaces which cooperate with a pair of axial support surfaces on the drivers of the basic body for the transfer of positive axial forces between the coupling part and the drivers. The coupling part of the loose top includes a pair of side contact surfaces which cooperate with a pair of side support surfaces on the drivers of the basic body for the transfer of torque and negative axial forces between the coupling part and the drivers. The pair of side contact surfaces define two laterally projecting male members arranged to engage two corresponding seats defined by the pair of side support surfaces of the drivers in an axially locking position. The pin of the loose top includes a surface for turning the pin and the loose top by cooperation with the screw.

There is a need to provide tooling that allows for utilizing the power curve of the modern machine tools, while accommodating the desire to drill at higher speed rates and lighter feed rates, but ultimately higher penetration rates.

According to the invention, there is provided a drilling system for producing deep holes in a workpiece, the drilling system comprising: a holder body having at least a first mounting screw hole extending along an axis; a drill head attachable to the holder body, with the holder body having a top surface forming a first mating surface, and the drill head having a bottom surface forming a second mating surface that engages the first mating surface of the holder body when attached thereto, wherein the drill head has at least a second mounting screw hole extending along an axis; at least one dovetail protrusion and at least one corresponding dovetail groove, with the at least one protrusion or groove formed on the opposing first and second mating surfaces, wherein the drill head is assembled to the holder body by rotating the drill head relative to the holder body about the axis of the tool until the at least one dovetail protrusion engages with the at least one dovetail groove and locks the drill head into place in association with the holder body, and at least one screw attaching the drill head to the holder body, wherein the at least one screw has a conical head and the drill head has a conical seat for receiving the conical screw head, and wherein the axis of the at least a first mounting screw hole and the axis of the at least a second mounting screw hole are arranged to line up such that when the at least one screw is received in the first and second mounting screw holes and tightened, the conical seat of the screw head causes the drill head to rotate about is center axis in the direction of tool rotation until the at least one dovetail protrusion engages with the at least one dovetail groove, and the at least one screw carries substantially no load during drilling.

The drill system better uses the power curve of the modern machine tools. The drill system uses a two-step drill, utilizing IC inserts to perform the major hole diameter cutting, and a central drilling system. In examples, the IC inserts can be set in a drill head in a single or double effective configuration. A central drilling system cuts the remaining minor diameter portion of the hole, and is configured to see less cutting surface footage, due to its position from the rotating center of the tool. The central drilling system may include a "self-centering" geometry, such that the drill head of the tool with be guided throughout the depth of the hole. The drill system allows for a large diameter deep hole that remains straight throughout to be drilled at higher speed and lighter feed rates thus offering a more productive tool that takes advantage of the power curves and lower thrust capabilities of modern machine tools.

Both the indexable IC inserts and central drilling system may provide the flexibility of being able to have different cutting geometries to suit a user's application, with various options available with the IC inserts and central drilling system. Each geometry can be suited to a specific material and/or application, thereby increasing the effectiveness of the system. In another aspect, additional economy and flexibility may be provided by a range of fixed diameter heads that fit on the same holder body, which provide the user the ability to drill multiple sized holes without the purchase of additional holder bodies.

In a further example, a plurality of dovetail protrusions and a plurality of dovetail grooves may be used, each of which is formed in a rotational pattern about the center axis of the tool. A central positioning system may be provided to allow alignment of the drill head to the holder body.

In an example, the at least one dovetail protrusion and groove are together designed to absorb the cutting forces during a drilling operation in two directions. The first and second mating surfaces of drill head and holder body together translate the axial force from drill head to body. The at least one dovetail groove and dovetail protrusion formed on one of the first and second mating surfaces respectively include surfaces that translate the rotational force from drill head to the holder body. These surfaces of the at least one dovetail groove and dovetail protrusion may be angled to oppose lateral loads from drilling forces.

Referring now to <FIG>, an example of the drilling system <NUM> of the invention may include a holder body <NUM> with shank end <NUM> to connect with the machine tool and a head end <NUM>. The length of this body <NUM> will be the determining factor of the depth of hole to be drilled. In the example shown, the holder body has two flutes to evacuate chips of material from the double effective cutting geometry of the drill head <NUM>. The drill head <NUM> in this example is assembled to the end of the holder body <NUM>. The drill head <NUM> supports and positions a plurality of indexable inserts <NUM> and a central drilling system <NUM>, that together perform the cutting action. Drill heads <NUM> of different major diameter and cutting configurations can be assembled to the holder body <NUM>, allowing for significant flexibility in allowing different cutting geometries to suit the application. Both the inserts <NUM> and central drilling system <NUM> can be changed out of the drill head <NUM> based on the materials and/or application of the user. The replaceable nature of the indexable inserts <NUM> and the central drilling system <NUM> that can be assembled to the drill head <NUM> allow the user to specify the type of geometry to be used in each insert based on the application. Each geometry can be suited to a specific material and/or application thereby increasing the effectiveness of the system <NUM>. Additionally, further economy and flexibility is provided by having a range of fixed diameter drilling heads <NUM> that fit on the same holder body <NUM>, to provide the user the ability to drill multiple sized holes without the purchase of additional bodies.

To further refine the system <NUM> in this example, the drill heads <NUM> are made to fit like sized bodies <NUM> with a predetermined interface <NUM> designed for that drill diameter range. As seen in <FIG>, all IC cutting inserts <NUM> as well as the central drilling system <NUM> are assembled to the drill head <NUM>. The central drilling system <NUM> can be a replaceable blade style or replaceable tip drill style, and is assembled with the mechanical means of assembly for that style and having the features to locate the central drilling system <NUM> in a predetermined position as part of the drill head <NUM>. The drill head <NUM> further includes pockets <NUM> to position the IC inserts <NUM> in the proper position to perform the major diameter cutting. The IC inserts <NUM> may mechanically fastened into the pockets <NUM> in precise position for cutting the outside diameter of the desired hole. The drill head <NUM> may include a center guide post <NUM>. In an example, the drill head <NUM> is then assembled to the body <NUM> and fastened using torx driven screws <NUM> with conical shaped heads <NUM>, as shown in <FIG>. The axis of the mounting screw hole <NUM> in the holder body is designed to line up with the axis of the mounting screw hole <NUM> in the drill head in such a way that, when tightened, the conical seat of the screw head <NUM> will influence the drill head <NUM> to rotate about its center axis in the direction of tool rotation until the connection <NUM> engages the holder body <NUM>.

Referring to <FIG>, the connection <NUM> between drill head <NUM> and body <NUM> is shown in more detail, and is designed to connect the drill head <NUM> and body <NUM> in a manner to more effectively absorb the cutting forces during a drilling operation, and more particularly, the cutting forces in two directions. As seen in <FIG>, the surface that translates the axial force from drill head <NUM> to body <NUM> is the flat face <NUM> of the body <NUM>, and the flat surface <NUM> on the bottom of the drill head <NUM>. In the surface <NUM> of the body <NUM>, dovetail grooves <NUM> are formed and correspondingly, dovetail protrusions <NUM> are formed in the drill head <NUM>. The surfaces that translate the rotational force from drill head <NUM> to body <NUM> are the faces <NUM> of the dovetail grooves on the body <NUM> and the faces <NUM> of the dovetail protrusions <NUM> on the drill head <NUM>. In this example, at least one dovetail groove <NUM> and at least one dovetail protrusion <NUM> may be provided, and a plurality of dovetail grooves <NUM> and dovetail protrusions <NUM> may be used as shown, disposed on opposing sides of the mating surfaces <NUM> and <NUM>. It may be possible to form the dovetail groove(s) <NUM> and/or dovetail protrusion(s) <NUM> on either one of mating surfaces <NUM> and <NUM>. In the example, symmetrical positioning of the grooves and protrusions is shown, providing balanced and effective absorption of the drilling loads. On each side of the interface <NUM>, there may be provided two grooves <NUM> on the body <NUM> and two interfacing protrusions <NUM> on the drill head <NUM>. All other surfaces of this interface are clearance. The interface of this example connection <NUM> is symmetrical which will allow for the head to be assembled successfully at <NUM>° increments or other suitable increments for example.

In this example, with reference to <FIG>, the dovetail protrusions <NUM> of the drill head <NUM> and the dovetail grooves <NUM> in the body <NUM> are formed in a rotational pattern about the center axis of the tool in a manner that first allows the drill head center guide post <NUM> to be inserted into the body center guide post hole <NUM> as seen in <FIG>. The drill head <NUM> may then be rotated about the axis of the center post <NUM>, in the direction of tool rotation (clockwise), as seen in <FIG>. As the drill head <NUM> is rotated, the dovetail protrusions <NUM> of the drill head <NUM> engage with the dovetail grooves <NUM> on the body <NUM> as seen in <FIG>, and lock into place as in <FIG>.

In the example, the connection between the body <NUM> and drill head <NUM> provides further distinct advantage. In a drilling process, lateral drilling forces have led to the use of screws and/or an insertable post or boss to attempt to counteract such lateral loading. Also, attempts to prevent tipping or rocking of a drill head against a holder body from lateral loading due to drilling forces has included putting these screw and/or bosses in bending. In such attempts, the position of these features relative to the point on the drill head where lateral loading is introduced increases the bending moment. In contrast, the present invention provides a connection between the body <NUM> and drill head <NUM> which effectively handles the lateral loading differently. The engaged surfaces <NUM> and <NUM> (see <FIG>) of the dovetail grooves <NUM> and protrusions <NUM> may be oriented at angles, such as <NUM>° to <NUM>°, or for performance, <NUM>° to <NUM>°, with an angle of <NUM>° shown in the example. The angled surfaces allow any and all components of lateral loading to be opposed by at least two of these features. The first function of the angled surfaces is to translate the torque from the tool into axial motion, drawing the drill head <NUM> onto the seating surface of the holder body <NUM>. Their second function is that when the angled surfaces are engaged, it will prevent tipping or rocking of the drill head <NUM> on the holder body <NUM>. In <FIG>, there is shown the engaged surfaces of the drill head <NUM> and holder body <NUM> as well as the dovetail features with lines at <NUM>. The opposing arrows <NUM> in the main cross sectional view show how these dovetail features create an effective clamp on each of the features with which they are engaged, so as to positively hold the drill head <NUM> onto the mating surface of the holder body <NUM>. Further, because these features are symmetrical they create the effect of opposing wedge shapes which would not allow any degrees of freedom once assembled.

The center guide post <NUM> of the drill head <NUM> inserts into the corresponding center guide post hole <NUM> in the body <NUM>. This feature acts as a positional guide ensuring that, when assembled, the drill head <NUM> and the body <NUM> share the same axis of rotation within set tolerances, and allows for proper alignment of the dovetail grooves and dovetail protrusions.

As described above the center guide post <NUM> and the mounting screws <NUM> only act as a means of guiding the assembly of the drill head <NUM> to the holder body <NUM>. The purpose of the mounting screws is to ensure proper assembly of the drill head and body. Once tightened in place the drill head and body will be assembled and ready to be used to drill. The mounting screws carry no load during drilling because all of the load is translated through the drill head and body interface. Once the dovetail surfaces are engaged, the influence of the mounting screws and guide post are negligible. This keeps the center post <NUM> and mounting screws <NUM> from being loaded in bending and concentrates all of the opposing lateral loads at the immediate connection <NUM> interface.

In this example, the drilling system may be designed to operate with through tool coolant. As seen in <FIG>, the drill head <NUM> may include four outlets, including two inner outlets <NUM> designed to direct a supply of coolant to the central drilling system <NUM> and two outer outlets <NUM> designed to direct a supply of coolant to the major diameter cutting inserts <NUM>. A large central coolant hole <NUM> formed in the holder body <NUM> will carry the coolant from the machine tool, through the body <NUM>, and towards the drill head <NUM>. In this example, as seen in <FIG>, the arrows show the coolant that supplies the two inner outlets <NUM> will travel through a main central coolant channel <NUM> formed in the body <NUM>, which breaks out into the center guide post hole <NUM>. From there, the coolant travels into the drill head <NUM> through a central channel <NUM> in the bottom of the center guide post <NUM>. The two inner outlets <NUM> are angled to intersect this main channel <NUM> in the drill head <NUM> and release the coolant near the central drilling system <NUM>. In <FIG>, the arrows show the coolant that supplies the two outer outlets <NUM> will travel through the main central coolant channel <NUM> of the holder body <NUM> towards the drill head <NUM>. Two outlets <NUM> extend from the face of the body <NUM> and angle inward to intersect with the main coolant channel <NUM>. The coolant will travel through these angled outlets <NUM> where they connect with the outer outlets <NUM> of the same diameter on the bottom seating surface of the drill head <NUM>, such that the coolant is released near the outside diameter of the drill head <NUM> towards the major diameter cutting inserts <NUM>. Other configurations to apply coolant at the locations of the cutting inserts <NUM> and <NUM> may be used.

The major diameter cutting inserts <NUM> may be indexable IC inserts, such as shown in <FIG>. In this example, trigon inserts are shown, having three cutting edges, and include a wiper <NUM>, being a feature on the insert <NUM> that is formed on the part of the insert cutting the major OD. The wiper <NUM> is generally positioned to be vertical in line with the center axis of the hole being drilled. The wiper surface has a small amount of clearance <NUM> behind the cutting edge as seen in <FIG>. The wiper <NUM> avoids the formation of surface defects from the cutting edge having a single point of contact between the tool and the work piece, such as if a corner radius is used instead of the wiper <NUM>. A single point contact can result in visible grooves in the surface finish of the hole, but also will not act to stabilize the tool. The wiper <NUM> allows the drill system to form a finished hole configuration with improved surface finish of the work piece, especially at tool break out. Additionally, the wiper <NUM> will provide stability to the tool at the point where the center drill exits the work piece. In the example shown, when the inserts <NUM> are set in a double effective configuration, there will be a wiper <NUM> cutting the major diameter on two sides of the tool, such as <NUM>° apart from each other. These opposing wipers <NUM> will act as a margin for the tool as it breaks out of the work piece on through holes. If the inserts <NUM> are set up in a single effective configuration, with only one wiper <NUM> on the insert cutting the major diameter, a wear pad can be used on the drill head <NUM> to oppose the wiper <NUM> and provide the stability for exit on through holes.

For the central drilling system <NUM>, a self-centering point geometry, such as on the AMEC T-A® blade and Gen3sys® replaceable tip drill of Allied Machine & Engineering Corp. , provide a combination of clearance features on the point of the blade that greatly increases its centering capability. The positive web cutting edge geometry allows for free mechanical chip forming at the drill center. These features benefit the design by producing a hole that starts on center and retains an overall increased straightness throughout the depth of the hole. This drilling system may utilize either of these two as the central drilling system, or another suitable system.

The design of the system <NUM> allows for a greater amount of drill diameter range with each holder body <NUM> as well as having the flexibility of tailoring the central drilling system <NUM> geometry to the application. The connection between the drill head <NUM> and holder body <NUM> also provides a structurally robust design that offers superior stability to the drilling head <NUM> during a drilling operation. Any volatility experienced in the drilling environment is handled by the connection between the drill head <NUM> and holder body <NUM>, and the stability of the drill head <NUM> in the present invention results in the cutting inserts <NUM> and <NUM> being supported to result in increased tool life and better hole quality. The connection between the body <NUM> and drill head <NUM> is also cost-effectively manufactured and makes assembly simple.

Claim 1:
A drilling system (<NUM>) for producing deep holes in a workpiece, the drilling system (<NUM>) comprising:
a holder body (<NUM>) having at least a first mounting screw hole (<NUM>) extending along an axis;
a drill head (<NUM>) attachable to the holder body (<NUM>), with the holder body (<NUM>) having a top surface forming a first mating surface, and the drill head (<NUM>) having a bottom surface forming a second mating surface that engages the first mating surface of the holder body (<NUM>) when attached thereto, wherein the drill head (<NUM>) has at least a second mounting screw hole (<NUM>) extending along an axis;
at least one dovetail protrusion (<NUM>) and at least one corresponding dovetail groove (<NUM>), with the at least one protrusion or groove formed on the opposing first and second mating surfaces, wherein the drill head (<NUM>) is assembled to the holder body (<NUM>) by rotating the drill head relative to the holder body about the axis of the tool until the at least one dovetail protrusion (<NUM>) engages with the at least one dovetail groove (<NUM>) and locks the drill head into place in association with the holder body, and at least one screw (<NUM>) attaching the drill head (<NUM>) to the holder body (<NUM>), wherein the at least one screw (<NUM>) has a conical head (<NUM>) and the drill head (<NUM>) has a conical seat for receiving the conical screw head (<NUM>),
characterised in that
the axis of the at least a first mounting screw hole (<NUM>) and the axis of the at least a second mounting screw hole (<NUM>) are arranged to line up such that when the at least one screw is received in the first and second mounting screw holes (<NUM>, <NUM>) and tightened, the conical seat of the screw head (<NUM>) causes the drill head (<NUM>) to rotate about is center axis in the direction of tool rotation until the at least one dovetail protrusion (<NUM>) engages with the at least one dovetail groove (<NUM>), and the at least one screw carries substantially no load during drilling.