Stepped deep-hole drilling tool with improved lubricating coolant supply

Abstract

The invention relates to a stepped deep-hole drilling tool with improved supply of the cutting edges with lubricating coolant and improved removal of the cuttings. In addition, the stepped deep-hole drilling tool can be produced economically.

Description

[0001] Title : Stepped deep drilling tool with improved

[0002] Cooling lubricant supply

[0003] Description

[0004] The present invention relates to a stepped deep drilling tool, which is preferably designed as a single-lip drill or as a double-lip drill.

[0005] Deep hole drilling tools are characterized by their ability to create deep holes relative to the diameter of the hole. This poses the problem of removing the chips created during drilling from the hole.

[0006] In deep hole drilling tools, this problem is solved by having a cooling channel inside the tool that extends from the clamping end of the tool to the drill bit tip. A fluid, such as drilling oil or a water-based emulsion or a mixture of cooling lubricant and air, is pumped through this cooling channel to the tip of the deep hole drilling tool. The fluid flows out of the hole via the chip flutes in the tool, carrying away the chips produced during drilling.

[0007] If a stepped hole is to be drilled into the workpiece, the cross-sectional area available inside the deep-hole drilling tool for the cooling channel is limited by the smallest diameter of the stepped hole in the deep-hole drilling tool known from the state of the art. Typically, a stepped deep-hole drilling tool is manufactured from a prismatic blank in which the cross-section of the cooling channel is the same from the rear clamping end to the drill tip.

[0008] The diameter of the drilling tool at the tip determines the diameter and cross-sectional area of ​​the cooling channel. This limits the volume flow of the cooling lubricant, so that the cutting edges at the tip and the various boring stages are insufficiently supplied with cooling lubricant. Furthermore, there is insufficient cooling lubricant available to remove the chips. This compromises process reliability, especially at high feed rates.

[0009] On special deep-hole drilling machines, attempts are made to counteract this limitation by significantly increasing the coolant pressure in order to generate sufficient flow despite small cooling channel cross-sections. However, even here, the achievable coolant flow rate is limited, and the energy requirements for the coolant pumps are very high.

[0010] The invention is therefore based on the object of providing a stepped deep drilling tool which avoids the disadvantages of the prior art and in particular allows an improved cooling lubricant supply while at the same time having moderate manufacturing costs.

[0011] This object is achieved according to the invention in a step deep drilling tool, comprising a shaft and a drill head, wherein at least one chip groove and at least one cooling channel are formed in the shaft and in the drill head, wherein the drill head has a tip, wherein at least one cutting edge is formed at the tip and each step, in that a cross-sectional area A KKS of the cooling channel(s) in the shaft larger than a cross-sectional area A KKB K of the cooling channel(s) in the drill head and / or that the number of cooling channels in the drill head is greater than the number of cooling channels in the shaft.

[0012] The large cross-sectional area of ​​the cooling channel(s) in the shaft of the stepped deep drilling tool significantly reduces the overall flow resistance of the cooling channels. The overall flow resistance of the cooling channels is made up of the flow resistance of the cooling channel(s) in the shaft and the flow resistance of the cooling channel(s) in the drill head. The overall flow resistance of the cooling channel(s) of the deep drilling tool according to the invention is determined primarily by the cooling channel(s) in the drill head and only to a small extent by the flow resistance of the cooling channel(s) in the shaft. The cooling channels in the drill head are relatively short compared to the overall length of the deep drilling tool. For example, they can make up 15%, 20% or 30% of the overall length of the civil engineering tool.As a result, the total flow resistance of the stepped deep drilling tool is significantly reduced if, according to the invention, the cross-sectional area of ​​the cooling channel(s) in the shaft is increased.

[0013] Ultimately, only the cooling channel(s) in the drill head act as a restriction, not the cooling channel(s) in the shank. As a result, all other conditions being equal, significantly more coolant reaches the drill tip and the cutting edges at the counterbore steps. This significantly improves the cooling of the cutting edges and the removal of chips from the drill hole.

[0014] Tests have shown that the volume flow in the cooling channel can be more than doubled by increasing the cross-sectional area of ​​the cooling channel in the shaft according to the invention, while maintaining the same pressure p KSSAt the end of the figure description and before the glossary, the measurement results of a drilling test are summarized in table form.

[0015] Alternatively or additionally, it is also possible to increase the number of cooling channels in the drill head compared to the number of cooling channels in the shank. This can also significantly reduce the overall flow resistance of the stepped deep hole drilling tool. In particular, it is possible to provide a kidney-shaped cooling channel in the drill head blank.

[0016] This kidney-shaped cooling channel has a relatively large cross-sectional area and supplies the tip of the stepped deep drilling tool according to the invention with cooling lubricant.

[0017] One or more steps of the step drill according to the invention (or the main cutting edges present there) can then be supplied with cooling lubricant using additional cooling channels (hereinafter also referred to as step cooling channels). The step cooling channels can be introduced into the drill head, for example, by erosion before or after grinding the drill tip. They are short because the steps of the step drill are arranged closer to the shank of the drill than the tip of the drill head. Therefore, the costs and effort for eroding these additional cooling channels are relatively low.

[0018] A particularly advantageous embodiment of the invention provides that the drill head and the shaft consist of two individual parts which are joined together in a material-locking manner.

[0019] For example, the connection point between the drill head and shaft can be designed as a soldering tang. This soldering tang is a positive connection in which one of the connecting parts is designed like a gable roof and the other part has a complementary recess. The two components, namely the shaft blank and the drill head blank, are soldered together in the area of ​​this connecting surface. Due to the design of the soldering tang, the contact surface and thus the connection surface is relatively large. In addition, the torque generated during drilling is transferred predominantly in a positive manner from the shaft to the drill tip, without the solder being subjected to bending or tensile stress. Rather, the torque is ultimately transferred via a compressive load through the soldering surface.

[0020] It is possible for the projection, which is part of the soldering tang, to be located on the drill head or on the shaft. The complementarily shaped recess is then arranged accordingly on the shaft or on the drill head.

[0021] It is also possible to join the green parts of the shaft and drill head before sintering, so that a component is created while the green parts are sintered (so-called sinter joining).

[0022] However, it is also possible to produce a blank for the stepped deep-hole drilling tool according to the invention from a single piece. The starting point is a green compact (or a pre-sintered brown compact) with an extruded "thin" cooling channel that is matched to the diameter of the stepped deep-hole drilling tool. This thin cooling channel can be expanded in the area of ​​the shaft before final sintering (so-called green compact machining). This machining can be performed by drilling, milling, and / or turning.

[0023] In a further advantageous embodiment of the invention, the deep drilling tool comprises one cutting edge (this is the case with a single-lip drill) or two cutting edges (this is the case with a double-lip drill) at the tip. Each cutting edge has at least one tip clearance surface.

[0024] One or two cooling channels of the drill head extend the entire length of the drill head and open into a clearance surface of each cutting edge. This ensures that each cutting edge at the tip of the drill is sufficiently supplied with coolant. This cools the cutting edges, and the chips generated there are reliably removed through the one or two chip flutes of the deep drilling tool.

[0025] In an advantageous development of the invention, a stepped cooling channel opens into a flank of each cutting edge of at least one step of the stepped deep-drilling tool. This ensures that the cutting edge(s) at this step are also cooled with cooling lubricant, and the chips generated there are similarly removed via one or two chip flutes.

[0026] It is not necessary for stepped cooling channels to be present on all steps of the stepped deep drilling tool. For example, if the stepped deep drilling tool has two steps and the rear step, i.e. the step further away from the tip of the deep drilling tool, only penetrates a few millimeters into the material, then it is not necessary to remove the chips generated at the second step with the aid of cooling lubricant. They are removed by the chips generated at the tip of the drilling tool or at the steps further forward and the

[0027] Cooling lubricant is carried along in the chip groove(s). In a further advantageous embodiment of the invention, a transfer chamber is formed at the connection between the drill head and the shaft, and the cooling channel(s) of the shaft and the cooling channel(s) of the drill head open into the transfer chamber.

[0028] This transfer chamber thus makes it possible to compensate for the different positions and cross-sections of the cooling channel(s) in the shaft and the cooling channel(s) in the drill head. Furthermore, the cross-sectional area of ​​the cooling channels in the shaft is reduced to the cross-sectional area of ​​the cooling channels in the drill head in the transfer chamber.

[0029] Such a transfer space can be easily created by grinding a groove into the protrusion of the soldering tang. This groove is easy to manufacture. Depending on the desired size of the transfer space, it can be easily and reliably varied by adjusting the depth of the groove.

[0030] It is particularly advantageous if both the shank and the drill head are made of carbide. This provides the necessary stability and rigidity of the tool and ensures particularly good concentricity and a low tendency for the cutting edge(s) to wobble in the steps. This is particularly important for stepped holes.

[0031] The shaft and drill head are preferably made from different raw bars that are available on the market as standard products. The raw bars for the shaft and drill head have the same outer diameter. They can be made from the same or different types of carbide. In any case, they differ in terms of the arrangement, shape and / or number of cooling channels. The cooling channel(s) of the raw bar of the shaft has one (in the case of a single-lip drill) or two (in the case of a double-lip drill) cooling channels, which are optimized in terms of their cross-sectional area.

[0032] The raw bar for the drill head has one or more cooling channels optimized for the outer diameter of the smallest step or the drill tip. Often, the raw bars for the drill head are also available on the market with a smaller kidney or smaller cooling channels and are therefore relatively inexpensive to purchase.

[0033] However, it is also possible for the shaft to be made of steel and only the drill head to be made of carbide. If the shaft is made of a steel tube (with one or two flutes), then the cross-sectional area of ​​the cooling channel in the shaft is larger than the cross-sectional area of ​​the cooling channel(s) in the drill head.

[0034] In short : The preferred combination consists of a tubular shaft made of steel and a drill head made of carbide .

[0035] To reduce wear on the cutting edges, both at the drill tip and on the steps, it is preferred if at least the drill head is coated with an appropriate protective layer. It is also possible for the drill head to be coated with a different coating than the shaft. All features described in the drawings, their description, and the claims can be essential to the invention both individually and in any combination.

[0036] drawing

[0037] They show:

[0038] Figure 1: a schematic diagram of a stepped deep drilling tool without stepped cooling channels,

[0039] Figure 2: a schematic diagram of a stepped deep drilling tool with stepped cooling channels,

[0040] Figure 3: the shaft of an embodiment before joining with the drill head,

[0041] Figure 4: the drill head of an embodiment before joining with the shaft,

[0042] Figure 5: shows a round-ground semi-finished product after soldering and round grinding and before the introduction of chip groove and grinding,

[0043] Figure 6: Side views of a deep drilling tool according to the invention,

[0044] Figure 7: detail X from Figure 6,

[0045] Figure 8: Sections and a front view of a deep drilling tool according to the invention, Figure 9: a representation of the transfer area at the

[0046] Joint between drill head and shaft with step

[0047] Cooling channels and

[0048] Figure 10: a representation of the transfer space at the joint between drill head and shaft without stepped cooling channels.

[0049] Description of the exemplary embodiment

[0050] Figures 1 and 2 show simplified representations of two stepped deep drilling tools according to the invention. These sketches are intended to illustrate the principle of the invention. The invention is explained in detail with reference to Figures 3 ff.

[0051] A step deep drilling tool designed as a single-lip or double-lip drill comprises a shaft 1 and a drill head 9 .

[0052] The shaft 1 and the drill head 9 are connected to each other by a solder joint 21. The drill head 9 comprises a tip 31 and a step 25. Main cutting edges (without reference symbols) are formed on both the tip 31 and the step 25.

[0053] In the area of ​​the shaft 1 there is a cooling channel 7 which has a large diameter and a large cross-sectional area A KKS has .

[0054] In the area of ​​the drill head there is a cooling channel 17 which has a relatively small diameter and a relatively small cross-sectional area A KKBK In the area of ​​the soldering tang 21 , a transfer chamber 41 is formed which hydraulically connects the channels 7 and 17 .

[0055] Due to the large diameter and cross-sectional area of ​​the cooling channel 7, significantly more cooling lubricant can be delivered to the tip 31 of the drilling tool, all other conditions being equal. This increases its performance. Furthermore, tool life is increased and process reliability is improved.

[0056] In the embodiment shown in Figure 2, two additional cooling channels 15 are provided on the drill head 9. They specifically supply the cutting edges located at the step 25 with cooling lubricant. They generally begin in the transfer chamber 41.

[0057] With the aid of the cooling channels 15 and 17, the cooling lubricant flowing through the shaft 1 into the transfer chamber 41 can be distributed or divided between the drill tip 31 and the step 25. Due to the larger cross-section of the cooling channel 7 in the shaft area, sufficient cooling lubricant is available to both the cooling channel 17 and the cooling channels 15.

[0058] In Figures 3 and 4, the individual parts from which the embodiment described below is composed are shown individually and in different views.

[0059] Figure 3 shows a blank bar of a drill shank 1 in two different views. The drill shank 1 does not yet have a chip groove. Therefore, it is also referred to as a "blank bar." The drill shank 1 includes a clamping end 3. There, the stepped deep drilling tool is clamped in a drilling machine (not shown).

[0060] At an end of the shaft 1 opposite the clamping end 3, a recess 5 is formed, which is part of a so-called soldering tang. More on this later.

[0061] As can be seen from the right-hand view in Figure 3, a cooling channel 7 is formed in the shaft 1. The cooling channel 7 extends from the clamping end 3 to the recess 5. It has a kidney-shaped cross-section. In the stepped deep drilling tool according to the invention, the cross-sectional area A KKS of the cooling channel 7 as large as possible.

[0062] The shank 1 shown in Figure 3 has a cooling channel 7 because it is used to produce a single-lip deep-drilling tool. If the shank 1 belongs to a double-lip deep-drilling tool, then the shank 1 generally has two cooling channels (not shown).

[0063] Figure 4 shows a drill head 9. The drill head 9 has a projection 11 at one end, which is complementary to the recess 5 in the shaft 1. In the illustrated embodiment, the projection 11 has the shape of a gable roof with two flat surfaces that enclose an angle of 90° to each other. Accordingly, the complementary recess 5 also consists of two surfaces that enclose an angle of 90°.

[0064] A groove 13 is ground into the projection 11. This groove 13 forms the transfer space 41 between the cooling channel 7 of the shaft 1 and the cooling channels 15 and 17 in the drill head 9 in the finished deep drilling tool.

[0065] The cooling channels 7, 15 and 17 as well as the groove 13 are not shown in Figures 3 and 4 only in the side views.

[0066] In the left view of Figure 4, cooling channels 15 and 17 as well as the transfer chamber (without reference symbol) are visible. The cooling channels 15 and 17 open into the groove 13 and the transfer chamber 41, respectively. The cooling channel 17 also has a kidney-shaped cross-section; its cross-sectional area A KKB However, K is smaller than the cross-sectional area A KKS of the cooling channel 7 in the shaft 1 .

[0067] In the illustrated embodiment, the cooling channels 7 in the shaft 1 and 17 in the drill head 9 have a kidney-shaped cross-section. They extend over the entire length of both the shaft 1 and the drill head 9.

[0068] In this embodiment, the shaft 1 and the drill head 9 are made of solid carbide. The green compacts of the subsequent carbide components are produced by extrusion. During extrusion, the cooling channels 7 and 17, respectively, are introduced into the green compacts. They are therefore already present before sintering. The optional cooling channels 15 in the drill head 9 are generally introduced by erosion after sintering.

[0069] Figure 5 shows a blank of a stepped deep drilling tool 23 according to the invention, composed of the shank 1 and a drill head 9, without a chip groove and without a grind. The steps 25 and 27 are visible. Figure 6 shows the finished single-lip drill with a chip groove 19 and a grind.

[0070] The embodiment shown in Figure 6 is a single-lip drill with a chip groove 19. If the stepped deep drilling tool according to the invention is designed as a double-lip drill, then two chip grooves are present.

[0071] The soldering tang 21 is clearly visible in Figure 6. The soldering tang is the connection point between the projection 11 of the drill head 9 and the recess 5 of the shaft 1. At this point, the components shaft 1 and drill head 9 are connected to one another by soldering or another joining method. The shape of the soldering tang 21 with a projection and a recess is advantageous in that it enlarges the joining surface and enables good transmission of the torque during drilling from the shaft 1 to the drill head 9.

[0072] As can be seen from Figures 5 and 6, the diameter of the clamping end 3 is slightly reduced compared to the actual shank 1. This is often done to match the diameter of the clamping end 3 to the diameter of "conventional" chucks. If, for example, the diameter of the drill is 10.8 mm, the diameter of the clamping end 3 can be reduced to 10 mm and a standard chuck with a 10 mm diameter can be used. However, the diameter of the clamping end can also be larger than or the same as the shank diameter. A steel sleeve can also be soldered on to serve as an interface to the machine spindle.

[0073] Detail X from Figure 6 is shown enlarged in Figure 7. The cutting edges of the stepped deep drilling tool 23 will now be explained in more detail with reference to Figure 7. "29" denotes the rotation axis or center axis of the deep drilling tool 23.

[0074] In Figure 7, the cooling channel 17 with the kidney-shaped cross-section in the drill head is shown as a dashed / broken line.

[0075] As is usual with single-lip drills, a tip 31 is not located on the central axis 29 or rotational axis of the drilling tool. Rather, it is offset from it. The main cutting edge is designated "33" in Figure 7.

[0076] In a two-lip drill, the deep drilling tool is constructed centrally symmetrically and the tip is therefore located on the central axis 29 of the deep drilling tool.

[0077] The main cutting edge 33 has several clearance surfaces. In Figure 7, not all of the clearance surfaces are visible. The grinding of the drill tip can comprise four or five clearance surfaces: Two clearance surfaces are located behind the outer cutting edge (not visible). Further clearance surfaces are located behind the inner cutting edge and the tip 31 (not visible). Via these clearance surfaces, the main cutting edge 33 at the tip 31 of the deep drilling tool 23 is supplied with cooling lubricant. The clearance surface behind the outer cutting edge can also be curved (machined) so that it can be machined into the

[0078] Chip groove or into the oil space clearance at the chip groove.

[0079] A portion 35 of the center clearance surface behind the inner cutting edge is visible in Figure 7. The cooling channel 17 opens into this portion of the clearance surface 35. Finally, an oil chamber is ground into the clearance surface 35, which ensures that a partial flow of the cooling lubricant emerging from the kidney / from the cooling channel 17 can flow into the chip groove 19 with low flow resistance in order to remove the chips produced during drilling.

[0080] Spaced axially from the tip 31 is the first step 25. A cutting edge 37 is also formed on this first step 25. The flank associated with the cutting edge 37 is not visible in Figure 7.

[0081] In the illustrated embodiment, optional cooling channels 15 are shown. The cooling channels 15 supply the cutting edge 37 at the step 25 of the stepped single-lip drill with cooling lubricant. The cooling channel(s) 15 are generally subsequently introduced into the drill head 9, i.e., after grinding the steps 25 and 27. This can be done, for example, by erosion or other removal processes.

[0082] Both the cooling channel 17 and the cooling channels 15 open into the transfer chamber 41, which is not shown in Figure 7.

[0083] In this embodiment, the cutting edge 39 at step 27 is not supplied with cooling lubricant via stepped cooling channels. However, it is readily possible, and in some applications advantageous, to supply the cutting edge 39 at step 27 with cooling lubricant via one or two additional cooling channels, similar to the cutting edge 37.

[0084] Figure 8 shows two cross sections through the exemplary embodiment of the stepped deep drilling tool and a view of the tip 31 of the stepped deep drilling tool 23.

[0085] At the top of Figure 8, a cross-section through the shaft 1 with the cooling channel 7 is shown. In this cross-section, it is clearly visible that the only cooling channel 7 has a kidney-shaped cross-section. The corresponding cross-sectional area A KKS is as large as possible in order to minimize the flow resistance of the cooling channel 7 in the shaft 1. The cross-section of the cooling channel 7 can be selected to be relatively large because the diameter of the shaft 1 is large. It becomes particularly large if the shaft is made of a steel tube because its wall thickness can be selected to be relatively small.

[0086] The middle illustration of Figure 8 shows a cross section through the drill head 9 with one cooling channel 17 and two cooling channels 15.

[0087] From this illustration, it is clear that, firstly, the cooling channels 15 and 17 in the drill head are arranged closer to the center axis 23 of the deep hole drilling tool. This is due to the fact that in the finished deep hole drilling tool 23, the diameter of the drill head is reduced in two stages (see Figure 7). Naturally, the cooling channel 17 must not be "exposed" in the area between the step 25 and the tip of the drilling tool 23.

[0088] From the comparison of the cooling channels 7 in the shaft 1 and the cooling channels 15 and 17 in the drill head 9 it is clear that the cross-sectional area A KKS of the cooling channel 7 is much larger than the cross-sectional area A KKBK of the cooling channel 17 .

[0089] Even in total, the cross-sectional area of ​​the cooling channels 15 and 17 is smaller than the cross-sectional area A KKS of the cooling channel 7 .

[0090] In other words: The flow resistance of the cooling channel 7 is much lower than the flow resistance of the cooling channels 15 and 17. Therefore, the total flow resistance of the cooling channels 7, 17 and the optional cooling channels is reduced by just one cooling channel 7 with a large cross-sectional area in the shaft 1.

[0091] Compared with a conventional stepped deep drilling tool having a cooling channel 17 extending over the entire length of the stepped deep drilling tool 23, i.e. from the clamping end 3 to the tip 31, the volume flow could be increased by 50% at a delivery pressure of 100 bar, just by increasing the cross-sectional area of ​​the cooling channel 7 in the shaft 1.

[0092] If one or two additional stepped cooling channels 15 are introduced, the volume flow increases by more than 130%. It is therefore more than twice as large as with a conventional deep drilling tool! This leads to increased process reliability and an improvement in service life of 25% or more. At the end of the description of the figures, the results of a comparison of the volume flows of the cooling lubricant for a conventional stepped deep drilling tool (with a continuous cooling lubricant channel with a small cross-sectional area) and a stepped deep drilling tool according to the invention (with a stepped cooling lubricant channel which has a large cross-sectional area in the area of ​​the shank and in which the channel only has a small cross-sectional area in the area of ​​the drill head) are shown. These measurements impressively confirm the effects of the invention.

[0093] The lower part of Figure 8 shows a top view of the stepped deep drilling tool according to the invention. This illustration clearly shows that the kidney-shaped cooling channel 17 in the drill head 9 opens into the tip clearance surface 35 and supplies the cutting edge 33 at the tip of the stepped deep drilling tool with cooling lubricant.

[0094] Furthermore, it is clear that the optional stepped cooling channels 15 end at the step 25 and supply the cutting edge 37 present there with cooling lubricant.

[0095] The cutting edge at step 27 is not supplied with a separate cooling channel containing coolant. Rather, the amount of coolant flowing through the chip groove 19 is sufficient to adequately cool and lubricate the cutting edge 39 and to remove the chips generated there.

[0096] Figure 9 again shows a top view of a stepped deep drilling tool with a transfer space 41. The transfer space 41 is created by grinding a groove 13 into the projection 11 of the drill head 9. The contour of the cooling channel 7 in the shaft 1 is also shown with the help of a broken line. From a comparison of the cross-sectional areas of the cooling channel 7 in the shaft 1 and the cooling channels 15 and 17 in the drill head 9, it is clear that the cross-sectional area of ​​the cooling channel 7 is significantly larger than the sum of the cross-sectional areas of the cooling channels 15 and 17. It is also clear that the number of cooling channels 15 and 17 in the drill head 9 is greater than the number of cooling channels 7 in the shaft 1.

[0097] Figure 10 largely corresponds to Figure 9. However, in the embodiment shown in Figure 10, there are no stepped cooling channels 15.

[0098] The results of a drilling test in tabular form:

[0099] Maximum drilling diameter 10.6 mm; usable shaft length 134 mm;

[0100] Pressure of the cooling lubricant at the inlet to the cooling channel: 100 bar.

[0101] Glossary:

[0102] Deep hole drills or deep hole drilling tools are, as the name suggests, ideal for drilling deep holes or bores. A bore is considered deep if its depth T is greater than 10 x the diameter D of the bore (T > 10 x D). Deep hole drilling tools operate according to various systems familiar to those skilled in the art, such as BTA, ejector, single-lip drill, double-lip drill, etc.

[0103] A distinction is made between single-lip drills and double-lip drills for deep hole drilling. Single-lip drills and double-lip drills are long and slender. With single-lip drills, the tip of the drill bit does not coincide with the rotational or central axis; they have a relatively large chip flute through which the chips are removed. The single-lip drill centers itself in the hole.

[0104] With double-fluted drills, the drill tip coincides with the rotation axis of the double-fluted drill. This centers the drill tip in the hole. Double-fluted drills have two flutes that are smaller than the flute of a single-fluted drill.

[0105] What single- and double-lip drills have in common is that the chips are removed from the hole by a liquid (drilling oil or water-based cooling lubricant) that is pumped to the drill tip under high pressure. Cooling channels are designed in the drilling tools for this purpose. The liquid exits the cooling channel at the drill tip and flows out of the hole through at least one chip groove. In doing so, it takes the chips produced by the cutting edge(s) with it. Single- and double-lip drills are normally used in a diameter range of 3 mm to 40 mm. Holes with a length of up to around 6,000 mm are possible.

[0106] They can be used in machine tools such as lathes, machining centers or special deep drilling machines.

[0107] The machining process occurs through a relative movement of the drill to the workpiece in the direction of rotation around a common central axis or rotational axis, as well as a relative movement of the drill in the direction of the rotational axis (feed movement). The rotational movement can be caused by the drill and / or the workpiece. The same applies to the feed movement.

[0108] Cooling lubricant (oil or emulsion) or a mixture of cooling lubricant and air (minimal quantity lubrication) is pumped through the cooling channels in the drill shank and drill tip to lubricate and cool the drill head and guide pads. The cooling lubricant also transports the chips generated by the main cutting edges through the chip flutes.

[0109] The coolant is supplied at the rear end under pressure (for example, at 75 or 100 bar), passes through the cooling channel, and exits at the drill head or drill tip. The pressure depends on the diameter and length of the drill. The smaller the cooling channel and the longer the tool, the higher the pressure must be selected to ensure sufficient coolant flow for cooling and chip removal.

[0110] The drill head of a double-fluted drill has two main cutting edges, although it may also have multiple cutting edges. The cutting edge is the area involved in the machining process; it is formed by the rake face and the flank face. The rake face is the area over which the chip flows.

[0111] In a double-fluted drill, the main cutting edges or cutting edges extend from the center axis of the drill head to its outer diameter.

[0112] The flank is the surface at the tip of the drill head that faces the workpiece surface. A blunt drill bit can be sharpened again by grinding the flanks.

[0113] The overall shape of all cutting and non-cutting surfaces on the face of the drill head is referred to as the grind. This also includes surfaces that are not directly adjacent to the cutting edges, for example surfaces or grooves for directing the coolant flow or additional clearance surfaces or a point thinning to reduce the feed force. The grind largely determines the shape of the chips and is matched to the material being machined. The objectives of this match include the best possible chip shape, a high machining speed, the longest possible service life for the drill bit and compliance with the required quality characteristics of the hole such as diameter, surface or straightness (center line).

[0114] At least the drill head is made of a material suitable for cutting, usually carbide, but also cermet, ceramic or other suitable materials.

[0115] Sintered carbide with WC and Co components is usually used as hard metal.

[0116] Machining the workpiece wears the cutting edges of the drill bit. A blunt drill bit can be reworked through regrinding. Regrinding involves re-grinding the worn part of the drill bit until all worn areas (especially the chip and flank) are removed and new, sharp cutting edges are created. Afterward, the grind returns to its original shape. If necessary, a coating is applied to at least the tip of the drill bit after regrinding. The drill bit then has the same properties as a brand-new drill bit.

[0117] A drilling tool can be reground as often as necessary until a complete grinding can no longer be applied to the drill head or until the tool can no longer be guided sufficiently due to the shortening of the guide bevels and strips.

[0118] To increase service life, the drill head can be coated with a wear-resistant coating; usually from the metal nitride or metal oxide group, also in several alternating layers. The thickness is usually approximately 0.0005 to 0.010 mm. The coating is applied using chemical or physical vacuum deposition processes. The coating can be applied to the circumference of the drill head, the flank surfaces, or the rake faces; in some cases, the entire drill head can be coated.

[0119] During regrinding, the coating is removed by the grinding wheel, at least from the surfaces being reground. The coating remains intact on the other surfaces of the ground surface.

[0120] Two round ground lands are arranged around the circumference of a double-fluted drill. These lands guide the drill bit in the hole; they also smooth the hole wall. The round ground lands are cylindrical segments arranged at a distance of radius R (equivalent to half the nominal diameter of the drill bit) from the center axis.

[0121] List of reference symbols 1 Drill shank 3 Clamping 5 Recess

[0122] 7 Cooling channel

[0123] 9 Drill head

[0124] 11 projection 13 groove

[0125] 15 and 17 cooling channels in the drill head

[0126] 19 Bead or chip groove

[0127] 21 Soldering iron 23 Step deep drilling tool

[0128] 25, 27 level

[0129] 29 Rotation axis or central axis

[0130] 31 lace

[0131] 33 Main cutting edge at the tip 35 Tip clearance

[0132] 37, 39 cutting edge

Claims

Patent claims 1. Deep drilling tool comprising a shaft (1) and a drill head (9), wherein at least one chip groove (19) and at least one cooling channel are formed in the shaft (1) and the drill head (9), wherein the drill head (9) has a tip (31) and at least one step (25, 27), wherein at least one cutting edge (33, 37, 39) is formed on the tip (31) and each step (25, 27), characterized in that a cross-sectional area (A KKS ) of the cooling channel(s) (7) in the shaft (1) is greater than a cross-sectional area (A KKB K) of the cooling channel(s) (15, 17) in the drill head (9) and / or that the number of cooling channels (15, 17) in the drill head (9) is greater than the number of cooling channels (7) in the shaft (1).

2. Deep drilling tool according to claim 1, characterized in that the drill head (9) and the shaft (1) are integrally connected to one another.

3. Deep drilling tool according to claim 2, characterized in that a connection point between the drill head (9) and the shaft (1) is designed as a soldering tang (21).

4. Deep drilling tool according to claim 3, characterized in that the soldering tang (21) comprises a projection (1) extending in the direction of a central axis of the deep drilling tool (23) and a complementarily shaped recess (5).

5. Deep drilling tool according to claim 4, characterized in that the projection (11) is provided on the drill head (9) and the recess (5) on the shaft, or that the projection (11) is provided on the shaft (1) and the recess (5) on the drill head (9).

6. Deep drilling tool according to one of the preceding claims, characterized in that one or two cutting edges (33) are formed on the tip (31), each having at least one tip clearance surface (35), and in that a cooling channel (17) of the drill head (9) opens into a tip clearance surface (35) of each cutting edge (33).

7. Deep drilling tool according to one of the preceding claims, characterized in that on each step (25, 27) one or two cutting edges (37, 39) is / are formed with at least one step flank, and in that in at least one step (25) a (step) cooling channel (15) opens into a flank of each cutting edge (37).

8. Deep drilling tool according to one of the preceding claims, characterized in that a transfer space (41) is formed at the connection between the drill head (11) and the shaft (12), and that the cooling channel(s) (7) of the shaft (1) and the cooling channel(s) (15, 17) of the drill head (41) open into the transfer space (41).

9. Deep drilling tool according to one of claims 2 to 7 in conjunction with claim 8, characterized in that the transfer space (41) is formed by a groove (13) in the projection (11) of the soldering tang (21).

10. Deep drilling tool according to one of the preceding claims, characterized in that the drill head (9) is soldered to the shaft (1).

11. Deep drilling tool according to one of the preceding claims, characterized in that the shaft (1) consists of steel or a steel tube, and that the drill head (9) consists of hard metal.

12. Deep drilling tool according to one of the preceding claims, characterized in that the shaft (1) consists of hard metal and that the drill head (9) consists of hard metal.

13. Deep drilling tool according to one of the preceding claims, characterized in that at least the drill head (9) is coated.

14. Deep drilling tool according to one of the preceding claims, characterized in that it is a single-lip drill or a double-lip drill.

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