Single-lip drill

Abstract

Single-lip drill with at least one cutting edge formed on a drill head, which has at least one cutting edge (23), wherein the cutting edge (23) is assigned a chip breaker (25) for breaking chips cut by the cutting edge (23), and wherein the chip breaker (25) has a positive rake angle (γ BT ), characterized in that at least one chip splitter (24; 24') is arranged in the at least one cutting edge (23).

Description

State of the art

[0001] The invention relates to a single-lip drill according to the preamble of independent claim 1.

[0002] Single-lip drills are generally used for deep-hole drilling. Such single-lip drills, as well as other designs of deep-hole drills, are described in the VDI guideline VDI 3210. Single-lip drills are primarily used for drilling holes with a relatively small diameter, typically in the range of 0.5 mm to 50 mm, although the drilling depth can be several times the drill diameter.

[0003] Generally, single-lip drills consist of a drill head and a drill shank with a clamping end. The drill head has a cutting edge that extends from the drill's central axis to the drill circumference. Guide elements can also be provided on the drill circumference. The drill head and drill shank are either positively connected or are made from a single piece. There is at least one channel running through the drill shank and drill head, which has openings at the drill head and at the clamping end. Pressurized coolant is fed through this channel from the clamping end. This coolant exits at the drill head and, in addition to cooling the drill head or the cutting edge, has the particular task of flushing out the chips created during drilling through a V-shaped chip removal groove in the drill head and drill shank.

[0004] The single-lip drill described in DE 25 22 565 A1 contains an interchangeable insert that can be used on either side. The cutting edges on both sides of the insert each have a step for chip separation.

[0005] According to one embodiment, the cutting edge of a drill described in JP 59 196108 A1 has a notch that acts as a chip splitter. In another embodiment, a step is provided in the straight cutting edge, which has an undercut with a predetermined angle.

[0006] US 2009 / 0110501 A1 discloses a cutting tool used for deep-hole drilling. The cutting tool has a cutting head mounted on a shaft. The cutting head is asymmetrical with respect to a longitudinal axis and has at least one cutting edge. The cutting head has guide segments extending from a front end to a rear end of the cutting head. Each of the guide segments has a guide pad on its circumference. A front end of the guide pad rests on a cylindrical shell defined by the cutting diameter of the cutting tool. A rear engagement portion of the cutting head engages a front engagement portion of the shaft. The cutting head is made of sintered hard metal powders, and the guide pads are an integral part of the cutting head.

[0007] The drill described in utility model DE-G 74 41 010 has two cutting edges. Both cutting edges contain rectangular recesses that act as chip breakers. Due to the rectangular recesses, these chip breakers each have an undercut relative to the drilling direction.

[0008] In the single-lip deep-hole drill described in utility model DE 203 21 368 U1, however, the cutting edge is assigned a chip breaker, referred to there as a chip former. This chip breaker is arranged along the outer cutting edge and is intended to break off the drilling chips, thus enabling reliable removal of the drilling chips through a V-shaped groove in the single-lip drill. The cutting edge of the known single-lip drill has a straight standard grind with two straight cutting edges.

[0009] The chip breaker assigned to the cutting edge, as known from DE 203 21 368 U1, improves the formation of the drilling chips and thus increases the feed rate (feed / revolution) during drilling. However, this is only possible up to a certain extent. As the feed rate increases, even with such a chip breaker, the formation of the drilling chips becomes increasingly unfavorable, which can result in chips being created whose removal through the chip removal groove is no longer easily guaranteed. Instead, the chips can become jammed in the chip removal groove and thus cause blockages that damage the deep hole drill and / or the workpiece being machined. In the worst case, the chip blockage caused by chips becoming wedged between the bore wall and the chip removal groove can even lead to drill bit breakage, with the associated damage to the workpiece being machined.

[0010] Chip splitters do indeed divide the chips, thus reducing their size and thus improving chip removal. However, at high feed rates, the divided chips also tend to be quite long, which in turn leads to the disadvantages described above: chip jamming in the chip removal groove, with all the disadvantages described above.

[0011] The invention is therefore based on the object of providing a single-lip drill which enables a high feed rate while at the same time allowing unproblematic removal of the chips through the chip removal groove.

[0012] This object is achieved by the features specified in independent claim 1. Disclosure of the invention

[0013] The basic idea of ​​the invention is to provide a single-lip drill with both a chip breaker associated with at least one cutting edge and at least one chip splitter in the cutting edge. In other words, the advantages of chip breakers are combined with those of chip splitters. This results in a highly advantageous reduction in both the width and length of the chips. The combination of chip breaker and chip splitter results in very small and narrow chips during machining of the workpiece, which are transported away in a particularly optimal manner in the chip removal groove.

[0014] The single-lip drill according to the invention enables a significantly higher feed rate than conventional single-lip drills, which allows for a correspondingly higher production speed in industrial production. This allows feed rates more than three times higher than with conventional single-lip drills to be achieved.

[0015] The improvements are achieved through the advantageous shaping of the chips generated during drilling. The chip splitter(s) ensure that the chip is divided longitudinally, thus limiting the chip width. The chip breaker assigned to at least one cutting edge limits the length of the chips. Chip removal is thus ensured even with a reduced coolant supply. As a result, the single-lip drill according to the invention achieves a high level of process reliability. In particular, drill breakage, which would otherwise destroy the workpiece to be drilled, is reliably prevented by preventing clogging of the chip removal groove.

[0016] The single-lip drill according to the invention therefore has considerable advantages overall when used, particularly in industrial series production.

[0017] Further embodiments and developments of the single-lip drill according to the invention are the subject of the dependent claims.

[0018] A particularly advantageous embodiment provides for the at least one chip separator to be implemented as a groove. Alternatively, the at least one chip separator can be implemented as a step.

[0019] An advantageous embodiment provides that the number of chip dividers is determined depending on the diameter of the single-lip deep-hole drill, whereby with increasing drill diameter, a corresponding number of chip dividers can be provided.

[0020] The chip splitter(s) are arranged in / on the cutting edges, which feature a chip breaker. They are positioned in / on the cutting edges in such a way that they essentially divide the cutting edges into approximately equal-length sections, thus dividing the chip into several sections of essentially equal width.

[0021] A further embodiment provides that the chip splitter has a clearance angle of greater than 0° relative to a line parallel to the drill center line. The resulting undercut of the chip splitter effectively forms a cutting edge and increases the reliability of chip separation. A further development of this embodiment provides that the clearance angle is determined depending on the material of the workpiece to be drilled. The clearance angle is preferably in a range of 1° to 60°, especially in the range of 8° to 12°.

[0022] Chipbreakers are modifications arranged on the rake face of the tool with the purpose of breaking, shaping, or directing chips. The geometry of a chipbreaker is defined and described in relation to the tool cutting edge normal plane, i.e., the plane perpendicular to the cutting edge.

[0023] The chipbreaker's rake angle is the tangent angle of the chipbreaker at the point closest to the cutting edge. The chipbreaker's rake angle is preferably in the range of 10 to 30°, especially in the range of 15 to 25°.

[0024] The chip breaker is divided into two sections that fulfil different functions. The first section is used to guide the chips after they have been removed from the workpiece. This section can have various curvatures and preferably has a tangent angle that is as positive as possible. This means that the chip is only slightly deformed and can be removed easily. The transition from the first to the second section is defined by the transition from a positive to a negative tangent angle. The second section serves as the impact surface for the chips. This section is usually more curved and has increasingly negative tangent angles up to the point where the impact surface merges into the chip face. In this second section, the chips are increasingly deformed as they slide along until they break.

[0025] The shape of the chipbreaker depends on the material being machined and its formability, the process parameters, the coolant used, and other factors. The chipbreaker can have areas with varying tangent angles, thus compressing or deforming the chip sliding along the chipbreaker to varying degrees in different areas. The shape of the chipbreaker can also vary along the cutting edge to achieve optimal chip breaking.

[0026] The chip breaker distance is the distance from the cutting edge to the transition of the impact surface into the rake face. According to an advantageous embodiment, the distance is in the range of 0.1 to 2 mm, in particular in the range of 0.3 to 0.8 mm. The chip breaker distance can vary along the cutting edge.

[0027] According to an advantageous embodiment, the chip breaker can be designed as a molded recess or groove in the rake face of the tool. The surface forming the chip breaker is referred to as the chip breaker face. The angle between the rake face and the tangent to the chip breaker face is referred to as the tangent angle. It is positive if the angle between the tangent to the chip breaker face and the cutting direction is greater than 90°, with the tangent always pointing away from the cutting edge.

[0028] The chip breaker can be directly adjacent to the cutting edge or there can be an additional surface to protect the cutting edge, which is arranged between the cutting edge and the chip breaker.

[0029] It is understood that the invention is not limited to a chip breaker of the type described above, but in principle also covers all conceivable shapes of chip breakers, in particular shapes other than a U-shaped form.

[0030] According to an advantageous embodiment, the single-lip deep-hole drill can be composed of a drill head and a drill shaft, or the drill head and drill shaft can be made from a single piece. Alternatively, a replaceable drill head can be provided.

[0031] Further designs concern the drill head, which can be made of hard metal and / or coated, for example, with a hard material layer. These measures can significantly extend the service life of the single-lip deep-hole drill.

[0032] Further advantageous developments and refinements of the single-lip drill according to the invention are the subject of the following description.

[0033] Embodiments of the invention are illustrated in the drawing and explained in more detail in the following description.

[0034] They show: Fig. 1 a single-lip drill according to the prior art; Fig. 2 shows a first embodiment of a cutting edge of the single-lip deep-hole drill according to the invention; Fig. 3 the front view of the Fig. 2 shown deep hole drill; Fig. 4 shows a further embodiment of a cutting edge of a deep hole drill according to the invention; Fig. 5 the front view of the Fig. 4 shown deep hole drill and Fig. 6 shows a schematic and sectional view of a chip breaker as it can be used in a single-lip drill according to the invention. Description of implementation examples

[0035] Fig. Figure 1 shows a single-lip deep-hole drill 10 as is known from the prior art. The single-lip deep-hole drill 10 includes a clamping end 11 for receiving the single-lip deep-hole drill 10 in a Fig. 1, not shown in detail, and a drill shank 12 with a drill head 13. The drill shank 12 and the drill head 13 are made as a single piece. At least one coolant channel 14 is provided in the drill shank 12, which opens at the front end of the drill head 13. The coolant pumped through the coolant channel 14 not only has the task of cooling the drill head 13, but also serves to remove the chips produced during drilling through a V-shaped chip removal groove 15, which begins at the cutting edge 16 of the single-lip deep-hole drill 10 and extends almost over the entire length of the drill shank 12. At least one guide element 17 can be provided on the circumference of the drill head 13.

[0036] An embodiment of a deep hole drill according to the invention is shown in Fig. 2 and Fig. 3 shown schematically.

[0037] This deep hole drill has a cutting edge 23 that runs obliquely to the drill bit's central axis A. Associated with the cutting edge 23 is a chip breaker 25 that preferably has a positive rake angle and is designed, for example, as a U-shaped groove. The rake angle in the groove ranges from a positive value to 0° at the groove base in a first region and, in a second region, from 0° to a negative rake angle at the edge of the groove facing away from the cutting edge. This limits the length of the chip by sliding along the surface of the chip breaker as it is lifted off, being compressed there and breaking at a defined point. A chip divider 24, also in the form of a groove, is arranged in the cutting edge, for example. This groove runs obliquely to the cutting edge in such a way that an "undercut" is created in the feed direction.The chip splitter 24 has a so-called chip splitter clearance angle α relative to the drill center axis of greater than 0°.

[0038] The chip splitter is arranged in the cutting edge 23 in such a way that it divides the cutting edge into approximately equal length sections a and b. A chipped chip is thus also divided into essentially equal width sections a and b. Fig. 2 shows a single chip splitter in the form of the groove 24. It is understood that the invention is not limited to this, but that, in principle, several chip splitters can be provided, which in turn are preferably arranged such that they divide the cutting edge into sections of approximately equal length.

[0039] The chip splitter 24 divides the chip into two parts in terms of its width, whereas the chip breaker limits the chip in its length.

[0040] A tip 27 is followed by a further cutting edge 26 which cuts up to the central axis A and which, in this embodiment, does not have a chip breaker or chip splitter.

[0041] As in particular Fig. As can be seen in Figure 3, a coolant channel 28 is arranged in the drill head 22, through which coolant is supplied under pressure. This coolant also serves, in particular, to remove chips into the chip removal channel 30.

[0042] The single-lip drill according to the invention is characterized by having both a chip breaker 25 and a chip splitter 24. In this way, the chip is determined not only in terms of its length (by the chip breaker 25), but also in terms of its width (by the chip splitter 24). This results in small and narrow chips, which enable particularly optimal chip removal with the aid of the coolant supplied through the coolant channel 28 through the chip removal groove 30. In this way, the feed rate and, more generally, process reliability can be further improved.

[0043] Another embodiment of a single-lip drill according to the invention is shown in the Fig. 4 and Fig. 5, in which the same elements have the same reference numerals as in the Fig. 2 and Fig. 3, so that their description is fully referred to in the above statements. In contrast to the Fig. 2 and Fig. 3 illustrated embodiment is in the Fig. 4 and Fig. In the embodiment shown in Figure 5, the chip splitter is not implemented by a groove, but rather by a step 24'. This step 24' is also arranged such that it essentially divides the cutting edge 23 into approximately equally long parts a, b. It should also be noted here that not just one chip splitter, but several chip splitters can be provided - depending on the drill diameter. The step is also arranged obliquely to the drill center axis, i.e., it has a chip splitter clearance angle α relative to the drill center axis of greater than 0°, thereby forming an "undercut."

[0044] In Fig. 6 shows a chip breaker in cross-section. The chip breaker is not directly adjacent to the cutting edge 23, but at a distance d Bn . The distance of the chip breaker from the cutting edge I Bn is related to the cutting edge 23. The chip breaker is followed by a rake face A γ to.

[0045] Again Fig. As can be seen in Figure 6, the chip breaker has two areas I and II. In the first area I, the tangent angle γ BT < 0°, it goes into a negative tangent angle γ in the course of the chip breaker BT> 0° above. The first area I serves to guide the chips after cutting the workpiece. This area can, in principle, be curved in different ways, but preferably it has a positive tangent angle as shown. This means that the chip is only slightly deformed and can be easily removed. The transition from the first area I to the second area II is defined by the transition from the positive to the negative tangent angle. The second area II serves as the impact surface for the chips. This area is usually more strongly curved and has increasingly negative tangent angles γ. BT up to the point where the impact surface merges into the rake face. In this second area II, the chips are increasingly deformed as they slide along until they break.

[0046] The shape of the chip breaker, which is in Fig.6 is shown only as an example, can vary purely in principle and is determined depending on the material to be machined and its formability, the process parameters, the cooling lubricant used, and other factors. It is also possible in principle for the chip breaker to have more than two areas with different tangent angles, in order to compress or deform the chip sliding along the chip breaker to different degrees in different areas. The shape of the chip breaker, as well as the distances d Bn and I Bn can also vary along the cutting edge to achieve optimal chip breaking.

[0047] The chipbreaker rake angle is the tangent angle of the chipbreaker at the point closest to the cutting edge. The chipbreaker rake angle is preferably in the range of 10° to 30°, especially in the range of 15° to 25°. The chipbreaker distance, i.e., the distance from the cutting edge 23 to the transition of the impact surface into the rake face A, is γ is in the range of 0.1 to 2 mm, especially in the range of 0.3 to 0.8 mm.

Claims

[1] Single-lip drill with at least one cutting edge formed on a drill head, which has at least one cutting edge (23), wherein the cutting edge (23) is assigned a chip breaker (25) for breaking chips cut by the cutting edge (23), and wherein the chip breaker (25) has a positive rake angle (γ BT ), characterized by , in which at least one cutting edge (23) is arranged at least one chip splitter (24; 24'). [2] Single-lip drill according to claim 1, characterized by that the at least one chip splitter is realized as a groove (24). [3] Single-lip drill according to claim 1, characterized by that the at least one chip splitter is realized as a step (24'). [4] Single-lip drill according to claim 1, characterized by that the number of chip splitters (24; 24') is determined depending on the drilling diameter. [5] Single-lip drill according to claim 1, characterized bythat the chip splitter(s) (24; 24') divides the cutting edge (23) into approximately equally long sections. [6] Single-lip drill according to claim 1, characterized by that the chip splitter (24; 24') has a chip splitter clearance angle (α) relative to the drill center axis of greater than 0°. [7] Single-lip drill according to claim 1, characterized by that the rake angle is in the range of 10 to 30°, in particular in the range of 15 to 25°. [8] Single-lip drill according to claim 1, characterized by that the chip breaker (25) has at least a first region (I) for guiding the chips and at least a second region (II) for breaking the chips. [9] Single-lip drill according to claim 1, characterized by that the chip breaker (25) is positioned at a distance (I Bn ) of which at least one cutting edge (23) is arranged. [10] Single-lip drill according to claim 9, characterized bythat the distance (I Bn ) is in the range of 0.1 to 2 mm, in particular in the range of 0.3 to 0.8 mm. [11] Single-lip drill according to one of the preceding claims, characterized by that the chip breaker (25) is designed as at least one groove adjacent to the at least one cutting edge (23), in particular as a groove with a substantially U-shaped cross-section. [12] Single-lip drill according to claim 1, characterized by that the single-lip drill contains a drill head and a drill shaft and that the drill head and the drill shaft are made from one piece. [13] Single-lip drill according to claim 1, characterized by that the single-lip drill consists of a drill head and a drill shaft. [14] Single-lip drill according to claim 13, characterized by that the drill head is replaceable. [15] Single-lip drill according to one of claims 12 or 13, characterized bythat at least the drill head is made of a wear-resistant material, in particular hard metal. [16] Single-lip drill according to one of claims 12 to 15, characterized by that at least the drill head is at least partially provided with a coating.

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