Single-lip drill bit with replaceable guide strips for small bore diameters

Abstract

A single-lip drill comprising a drill head (11), wherein the drill head (11) comprises two replaceable guide strips (27), a groove and a coolant channel (43), wherein the drill head (11) has two recesses (41) for receiving the guide strips (27), wherein the recesses (41) have two parallel side surfaces (SF) and a base surface (GF), and wherein the coolant channel (41) opens into an end face or tip (19) of the drill head (11), characterized in that a width (BGF) of the base surface (GF) is at least 30% smaller than a distance (DSF) between the side surfaces (SF).

Description

[0001] The invention relates to a single-lip drill with replaceable guide rails with an improved supply of cooling lubricant.

[0002] Single-lip drills with replaceable guide rails and replaceable cutting inserts are known per se; for example, from DE 27 39 685 C2, DE 25 22 565 A1 or US 2011 / 0033255 A1.

[0003] DE 10 2009 013 270 B3 discloses a drill head with replaceable guide rails that feature a special design on their upper side facing the bore wall. Prism-shaped bevels are provided on the underside, which transfer the radial forces from the cutting tools to the upper side of the guide rail.

[0004] Replaceable cutting inserts and guide rails offer the advantage that, when necessary, only the worn cutting insert or guide rails need to be replaced. The actual single-lip drill is subject to much less wear than the cutting inserts and guide rails. It can therefore be used for significantly longer periods. Furthermore, the single-lip drill can be used for drilling various materials, for example, by using cutting inserts with a correspondingly adapted cutting geometry.

[0005] The cutting insert is inserted into a insert seat and the guide rails are inserted into recesses in the drill head and are each fastened to the drill head with the help of a fastening screw, which is screwed into the corresponding internal thread of the drill head.

[0006] A channel for coolant is provided in the drill shank and drill head. Pressurized coolant is pumped through this channel from the clamping end to the tip of the single-lip drill. The coolant exits there. It cools the drill cutting edge and lubricates the guide pads. The coolant flows back to the clamping end of the drill through a groove. The coolant transports the chips generated by the cutting edge out of the hole. The groove should be as large as possible to ensure smooth chip removal.

[0007] It is obvious that as the drill diameter decreases, the space available for the channel and the groove decreases. The aim is to select the cross-section or diameter of the coolant channel as large as possible so that a large amount of coolant can be transported through the channel to the tip of the single-lip drill with relatively low pumping power. On the other hand, the aim is also to make the groove as large as possible to ensure smooth chip removal. Furthermore, the remaining tool body must be sufficiently stable to withstand the static and dynamic loads during the drilling process and ensure the dimensional accuracy of the resulting hole.

[0008] In the area of ​​the drill head, a plate seat for the replaceable cutting insert and two recesses for the positive-locking mounting of the replaceable guide pads must be accommodated. Both the plate seat and the recesses must have at least one internal thread. If the drilling process requires longer guide lengths, two guide pads are arranged one behind the other in a recess. In this case, two internal threads are provided per recess or guide pad seat.

[0009] The insert and guide rails usually have stepped holes. Screws are inserted through these holes and screwed into the corresponding internal threads in the drill head, securely positioning and holding the insert and guide rails in the insert seat or recesses.

[0010] The internal threads of the cutting insert holder and the recesses must not touch the channel for the cooling lubricant, otherwise the channel would leak.

[0011] US 2011 / 0008116 A1, US 2011 / 0033255 A1, and EP 2216115 A1 describe an approach to remedy the "space problem" in the drill head of single-lip drills with a drill diameter of, for example, ten to twelve millimeters. The approach consists in providing two parallel cooling lubricant channels with a relatively small diameter in the drill shaft and in the drill head. These cooling lubricant channels open into a cooling lubricant groove formed on the outside of the drill head (see, for example, reference numeral 5 in the Fig. 1 of US 2011 / 0008116 A1). These measures also provide a large flow cross-section in the area of ​​the drill head.

[0012] Firstly, this approach is very expensive to manufacture, because creating two coolant channels is naturally more expensive than creating a single coolant channel. Furthermore, drilling such very small diameter holes is comparatively slow and prone to errors. Furthermore, for the same cross-sectional area, two small coolant channels have greater flow resistance than one coolant channel.

[0013] The invention is based on the object of providing a single-lip drill with replaceable guide rails and, optionally, a replaceable cutting insert, which is suitable for small bore diameters and enables improved coolant supply compared to the prior art. Furthermore, the drill should be cost-effective to manufacture.

[0014] This object is achieved in a single-lip drill with replaceable guide strips, comprising a drill head, wherein the drill head has a bead and a cooling lubricant channel as well as two recesses for the positive reception of the guide strips, wherein the recesses have two parallel side surfaces and a base surface, and wherein the cooling lubricant channel opens into an end face of the drill head, in that either a width of the base surface is at least 30% smaller than a distance between the side surfaces of the recesses or that a width of the side surfaces is at least 30% smaller than a depth of the recesses.

[0015] This means that the recesses do not have a rectangular cross-section. The inventive cross-sections of the recesses enable the required precise positioning and positive connection between the guide rails and the recesses. At the same time, they require less space in the drill head, so that, all other things being equal, more space remains between the recesses in the drill head of the single-lip drill. A channel for the cooling lubricant with a correspondingly larger diameter is provided there.

[0016] The inventive design of the recesses allows the cross-section of the coolant channel to be increased by approximately 40%, all other conditions remaining the same. This allows a significantly larger volume flow of coolant to be delivered to the tip of the single-lip drill. This improves the cooling and lubrication of the cutting edge and the guide pads, resulting in a longer service life for the cutting edge and the guide pads. Furthermore, the increased volume flow of coolant improves chip evacuation and prevents chips from becoming stuck in the chip channel / bead. This "sticking" is a common cause of spontaneous tool breakage during deep drilling. The increased volume flow increases process reliability in the drilling process.

[0017] The achievable drilling depth of a single-lip drill according to the invention is also increased compared to conventional single-lip drills. The flow resistance of the cooling channel(s) increases with increasing tool length and cooling channel length. In a single-lip drill according to the invention with a large-diameter cooling channel, extending the tool and, consequently, the cooling channel has a significantly less significant effect than in a single-lip drill with two small-diameter cooling channels.

[0018] Finally, the use of the single-lip drill according to the invention in drilling machines with cooling lubricant supply requiring only low pressures and flow rates allows for greater drilling depths and feed rates. Furthermore, productivity, process reliability, and service life are increased.

[0019] These advantages of the invention apply to single-lip drills of all diameters. Typical drill diameters currently range from approximately 10 mm to 45 mm, although the invention is not limited to these diameters.

[0020] The invention is particularly advantageous for single-lip drills with small diameters—for example, approximately 10 mm. It not only allows for increased drilling depths while simultaneously improving process reliability; some applications can only be realized with a single-lip drill according to the invention.

[0021] Typically, the diameter of the coolant channel for small drill diameters (i.e., from 9.5 mm to 12.5 mm) is about 20% of the drill diameter. It can also be 22% or even 25%.

[0022] Further advantages of the single-lip drill according to the invention include the fact that the production of a channel with a larger diameter is technically simpler than the production of a channel with a smaller diameter. Furthermore, the volume to be machined when milling the recesses in the drill head is smaller than with conventional single-lip drills. As a result, the machining time for producing the recesses can also be reduced in many cases.

[0023] Furthermore, the cross-sections of the inventive recesses have a lower notch effect than conventional recesses. This has a positive effect on the stability of the drill head and its ability to transmit high torques from the clamping end to the cutting insert.

[0024] In conventional single-lip drills with recesses that have a rectangular cross-section with sharp edges at the transition between the side surfaces and the base surface, the notch effect is considerable.

[0025] It has proven advantageous to provide at least one flat connecting surface between a lower edge of the side surfaces and a lateral boundary of the base surface. This connecting surface advantageously extends at an angle of approximately 45° between the base surface and the connecting surface. In other words, it halves the angle between the side surfaces and the base surface of the recess. This creates a particularly large amount of space for the coolant channel and reduces the notch effect of the recess, which is beneficial to the performance of the single-lip drill according to the invention.

[0026] Angles between the connecting surface and the base surface in the range of 30° and 60° have proven advantageous. For these reasons, an angle of 45° is preferable in many cases.

[0027] Alternatively, it is also possible to provide at least one step between the side surfaces and the base surface. This step, which can be shaped like a stair step, also reduces the volume of the recess compared to a conventional recess with a rectangular cross-section. Furthermore, the notch effect is reduced, so that the advantages of the invention are also realized with this cross-section of the recess.

[0028] It is also possible to provide a connecting surface with at least a single curve between the lower edge of the side surfaces and a lateral boundary of the base surface. This connecting surface can be concave or convex. In both cases, this results in an increase in the cross-sectional area in the drill head available for the coolant channel. Furthermore, the rounded transitions, for example, when the connecting surface is designed as a radius, further reduce the notch effect.

[0029] With a concavely curved connection surface, the notch effect is significantly reduced. With a convexly curved connection surface, the bore diameter of the coolant channel can be significantly increased.

[0030] As usual, the recesses extend in their longitudinal direction more or less parallel to a rotation axis of the single-lip drill.

[0031] A further advantageous embodiment of the invention provides that the recesses, unlike in the prior art, are not offset from one another by 90° in the circumferential direction, but rather that they are offset from one another by an angle β greater than 90° in the circumferential direction. An angle of 115° has proven particularly advantageous. An angular offset in a range between 100° and 118° is particularly advantageous in many cases.

[0032] The angle β between the guide rails or the recesses must not be arbitrarily large, because then the cross-section of the bead must be reduced accordingly.

[0033] A particularly advantageous embodiment and further development of the invention provides that a center point of the cooling lubricant channel is located midway between the connecting surfaces of the two adjacent recesses for the guide rails. This means that the wall thicknesses between the channel and the recesses for the guide rails are the same on both sides of the channel. This allows the diameter of the channel to be maximized.

[0034] A similar optimization proposes that the center point of the coolant channel be located midway between a cylindrical outer surface of the drill head and the insert seat of an interchangeable insert of the drill head. This also ensures that the wall thickness between the coolant channel and the outer diameter of the drill head or between the insert seat of the interchangeable insert is as large as possible, while simultaneously minimizing the weakening of the drill head.

[0035] The groove, which serves to evacuate the chips, is defined by a chip face and a wall. The chip face and the wall advantageously form an angle between 110° and 125°. An angle of 115° is preferred.

[0036] The invention also applies to the guide rails that are inserted into the recesses of the single-lip drill according to the invention. These guide rails comprise a guide surface, which is generally cylindrical and located on the outside when the guide rail is mounted, as well as at least two lateral boundary surfaces and at least one support surface. The lateral boundary surfaces run parallel to one another and the boundary surfaces and the support surface are arranged at right angles to one another. This is achieved in that a width of the support surface is at least 30% smaller than a distance between the boundary surfaces. In a further advantageous embodiment, a width of the boundary surfaces is at least 30% smaller than a thickness of the guide rail.

[0037] The guide rails according to the invention can be inserted into the recesses according to the invention and ensure a positive connection between the guide rails and the recesses which is just as good as with a conventional recess and a conventional guide rail with a square cross-section.

[0038] The lateral boundary surfaces of the guide rails are accommodated with zero or minimal play between the parallel side surfaces of the recess in the drill head. The support surface of the guide rail rests on the base surface of the recess, ensuring precise positioning and a positive connection between the recesses and the guide rails.

[0039] The tangential forces are transmitted between the lateral surfaces of the recess and the lateral boundary surfaces of the guide rails. The radial forces are transferred from the guide rail via the support surface to the base surface, thus enabling a very direct and efficient force transmission.

[0040] The guide rails can have flat connecting surfaces between the boundary surfaces and the support surface.

[0041] The angle between the support surface and the connecting surface can also be between 30° and 60°. 45° is preferred.

[0042] Alternatively, it is also possible to provide at least one curved connecting surface between the boundary surfaces and the lateral boundary of the support surface. This connecting surface can be convex or concave.

[0043] In any case, the notch effect is reduced and the cross-section available for the coolant channel in the drill shank is increased.

[0044] The guide rails are preferably made of hard metal. The drill head is also usually made of tempered steel. However, the invention is not limited to this material.

[0045] It's often advantageous to have a hard coating on the guide rail to reduce wear. The same applies to a replaceable cutting insert.

[0046] In order to place the cutting insert in a form-fitting and precise position on the drill head, an insert seat is provided at the tip of the drill head.

[0047] The guide surfaces of the guide rails are cylindrical, with the diameter of the cylindrical surface being equal to or smaller than the diameter of the single-lip drill.

[0048] In addition to the two guide rails in the drill head, a second group of guide rails may be present, which is arranged axially spaced from the first group of guide rails on the shaft 12 of the single-lip drill 1.

[0049] Further advantages and advantageous embodiments of the invention can be found in the drawing, its description and the patent claims. drawing

[0050] They show: Fig. 1 a simplified representation of a single-lip drill without interchangeable parts; Fig. 2 an isometric view of an embodiment of a single-lip drill according to the invention; Fig. 3 a front view (greatly enlarged) of the embodiment according to Fig. 2; Fig. 4 the embodiment according to Fig. 2 in two side views; Fig. 5 and Fig. 6 shows the tip of another embodiment of a single-lip drill according to the invention in an isometric view; Fig. 7 shows a front view of a second embodiment of a single-lip drill according to the invention; and Fig. 8 to 11 show different cross-sectional shapes of recesses and guide strips according to the invention. Description of the embodiments

[0051] In the Fig. 1 shows a single-lip drill 1 without interchangeable parts in a schematic and somewhat simplified manner. Fig. Some terms are explained in Figure 1. The single-lip drill 1 consists of a drill head 11, a profile shank 12, and a clamping end 13. The clamping end 13 is used to mount the single-lip drill in a deep drilling machine (not shown).

[0052] The drill head 11 according to the invention is generally used with brazed tools. In these cases, the drill head 11, a profile shank 12, and a clamping end 13 are brazed together. However, the invention is not limited to this type of tool. They can also be used with solid-shank tools, among others.

[0053] The rotational axis or center of the drill head 11 is designated by reference numeral 23. A groove is formed in the drill head 11 and the profile shaft 12, which groove is defined by a chip face 15 and a wall 17. The single-lip drill 1 according to the invention can have a diameter D of, for example, ten millimeters. This limits the cross-section of the drill head 11 and the groove.

[0054] In the Fig. 2 is an isometric view of a first embodiment of a single-lip drill according to the invention with interchangeable parts.

[0055] A tip is provided with the reference number 19. In the Fig. 2, a replaceable cutting plate 25 is clearly visible. Only the front ends of the guide rails 27 are visible in this illustration. Two internal threads 29 can be seen in the groove, which serve to secure one of the two guide rails 27 and a guide rail stop.

[0056] An outlet 31 of the cooling lubricant channel at the tip 19 of the drill head 11 is in the Fig. 2 also visible.

[0057] The Fig. 3 shows a front view, ie of the tip 19 of the single-lip drill. Fig. 3, the inserted cutting insert 25 and the screw head 33 used to secure the cutting insert 25 are visible. The cutting insert 25 is accommodated in a cutting insert seat 35 of the drill head 11. Details of the cutting insert seat are not explained in connection with this invention. However, two notes are permitted in this regard: A relief groove 37 is provided at the transition between two surfaces of the insert seat 35. It is part of the insert seat 35.

[0058] In the illustrated embodiment, the "base surface" of the insert seat 35 and the underside of the cutting insert 25 are not flat, but rather have several grooves that ensure a positive connection between the cutting insert 25 and the insert seat 35. The invention is not limited to single-lip drills with insert seats 35 configured in this way.

[0059] In the Fig. The guide rails 27 are clearly visible in Figure 3. They comprise a curved guide surface 39. The curvature of the guide surface 39 approximately corresponds to the diameter of the hole produced with the single-lip drill 1.

[0060] The guide rails 27 are accommodated in recesses 41, which have two parallel side surfaces SF and a base surface GF. The geometric details of the guide rails 39 and the recess 41 are shown in Fig. 8 to 11 illustrated and explained.

[0061] It is clear in the Fig. 3 that in this embodiment the recesses 41 between the side surfaces SF and the base surface GF have a flat connecting surface 45. This flat connecting surface 45 runs in the Fig. 3 at an angle of approximately 45° to the base surface GF. In this embodiment, it represents the angle bisector between the base surface GF and the side surfaces SF.

[0062] In the Fig. In Figure 3, the exit of channel 43 at the end face or tip 19 of the single-lip drill is clearly visible. Channel 43 has a circular cross-section. The flat connecting surfaces, designed as angle bisectors, create more space for channel 43 in the shaft of the single-lip drill. In other words, the diameter of channel 43 can be significantly increased compared to conventional single-lip drills, whose recesses have a rectangular cross-section.

[0063] Furthermore, it can be clearly seen that the center point M of the channel 43 is arranged in the middle between the connecting surfaces 45 of the two recesses 41 and in the middle between an outer diameter D and the insert seat 35 for the cutting insert 25m.

[0064] In this case, the distance between the center point M of channel 43 and the undercut 37, which is also part of the insert seat 35, is decisive. Undercut 37 is the closest distance to channel 43. Therefore, this distance is decisive for the location of the center point M of channel 43.

[0065] In this way, the cross-sectional area of ​​the drill head 11 present between the recesses 41, the outer diameter D and the insert seat 35 or the undercut 37 is optimally utilized in order to accommodate a cooling lubricant channel 43 with the largest possible diameter while at the same time ensuring a stable tool body or drill head.

[0066] In the Fig. 4 shows two side views of the single-lip drill according to the invention, by means of which the design of the drill tip 19 and the insert seat 35 can be explained in more detail.

[0067] In the Fig. Figure 4 shows the guide rails 27, which extend parallel to the rotation axis 23. The guide surfaces 39 are interrupted where the stepped holes for the fastening screws are located. This ensures that the screw head does not come into contact with the hole, but that only the guide surfaces 39 rest against the hole wall (not shown).

[0068] In the area of ​​the tip 19, the drill head 11 has a recess 47. The cooling lubricant channel 43 ends or opens into the recess 47. The recess 47, in turn, is designed so that the cooling lubricant emerging from the channel can reach the chip surface and the cutting edges of the cutting insert 45 directly. This achieves optimal cooling and chip removal. The invention is not limited to this particularly advantageous design of the tip.

[0069] The geometry of the recess 47 is shown in the Fig. 5 and Fig. 6 is also clearly visible.

[0070] In the Fig. Figure 7 shows a front view of another embodiment of a single-lip drill 1 according to the invention. In this embodiment, the connecting surfaces between the side surfaces SF and the base surface GF of the recesses 41 are designed as simply curved concave surfaces. This also significantly increases the installation space in the drill head 11 between the recesses 41. An advantage of this embodiment is the further reduced notch effect due to the "smooth" transition between the side surfaces SF and the base surface GF.

[0071] In the Fig. Figure 7 also clearly shows that an angle β, by which the recesses 41 are offset in the circumferential direction, is greater than 90°. The angle β can be, for example, 115°. It is very advantageous if it is less than 118°.

[0072] Because the angle β is greater than 90°, more space is created between the connecting surfaces 45 of the recesses 41, which benefits the diameter of the cooling lubricant channel 43.

[0073] Finally, the angle β can be selected so that the distance between the center point M of the cooling lubricant channel 43 to the insert seat 35 or to its undercut 37 and to the diameter D of the drill is the same as the distance between the center point M and the connecting surfaces 45 of the recesses 41. These distances are already determined based on the Fig. 3. This allows for optimal use of the installation space / cross-sectional area between the recesses 41, while limiting the angle β to the required extent so that the recesses 41 are not spaced further apart than necessary. A larger angle β ultimately leads to a reduction of the angle α, which generally offers no advantages.

[0074] "α" denotes the angle between the chip face 15 and the wall 17. They define the groove of the single-lip drill. In this example, the angle "α" is approximately 115°. The larger the angle α, the more volume is available in the groove for the removal of chips or coolant. Therefore, a large angle α is generally desirable.

[0075] Based on the Fig. 8ff show further cross-sections of the recesses 41 and the corresponding cross-sections of the guide rails 27. The guide rail 27 is not inserted into the recess 41. The thread and the hole for the fastening screws are also not shown.

[0076] In the Fig. Figure 8 shows an exemplary recess 41 of a first embodiment of a single-lip drill and a guide rail 27. In this embodiment, the connecting surface 45 between the side surfaces SF and the base surface GF of the recess 41 is designed as a flat connecting surface 47. It has an angle of 45° to the base surface GF and the side surfaces SF. That is, it is designed as an angle bisector.

[0077] In a corresponding manner, a flat connecting surface 47 is formed between the boundary surfaces BF and the support surface STF of the guide strip 27.

[0078] This makes it possible to insert the guide bar 27 into the recess 41, so that the lateral forces, i.e., the forces in the circumferential direction, are transmitted between the boundary surfaces BF and the side surfaces SF. The forces acting in the radial direction are transmitted to the base surface GF via the support surface STF of the connecting bar 27.

[0079] In the Fig. 9 shows an embodiment in which the connecting surfaces 49 and 51 are designed as curved surfaces.

[0080] The connecting surfaces of the recess 49 are designed as simply curved concave surfaces.

[0081] The connecting surfaces 51 of the guide rail 27 are designed as simply curved convex surfaces.

[0082] In the Fig. 10 shows an embodiment in which the transition / connection between the side surfaces SF and the base surface GF is produced by means of two flat (not curved) connecting surfaces 45 in the recess 41.

[0083] Accordingly, the guide rail 27 also has several flat connecting surfaces 47 at the transition between the boundary surfaces BF and the support surface STF.

[0084] In the Fig. Figure 11 shows an embodiment in which the curved connecting surfaces 49 and 51 are convexly curved at the recess and correspondingly concavely curved at the guide rail 27. This embodiment provides a particularly large amount of "additional" installation space in the drill head 1 for the channel 43.

[0085] The cross sections of the guide rails 27 according to the invention and the cross sections of the recesses according to the invention do not have to be geometrically similar. For example, and the cross sections shown in the Fig. 8, Fig. 10 and Fig. 11 shown guide rails 27 into the Fig. 9 shown recess 41. It is also possible to insert the Fig. 10 shown guide rail 27 into the Fig. 11 shown recess 41. The prerequisite is that the support surface STF of the guide rail 27 rests on the base surface GF of the recess 41, and that the width D BF the guide rail 27 to the width D SF the recess 41. List of reference symbols 1 single-lip drill 11 Drill head 12 profile shaft 13 clamping 15 chip surface 17 Wall 19 Pointed front side 23 Rotation axis of the single-lip drill 25 cutting plate 27 Guide rail 29 internal threads 31 (coolant) channel 33 screw head 35 insert seat 37 undercut 39 Guide surface 41 Recess for positively holding the guide rails 43 (Coolant) channel 45 flat connecting surface 47 flat connecting surface 49 curved connecting surface 51 curved connecting surface SF parallel side surface GF floor area B GF Width of the base area DSF Distance between side surfaces B SF Width of the side surface Lower edge of the side surface Lateral boundary of the base area β angle in circumferential direction between the recesses M Center of the coolant channel α Angle between chip surface and wall lateral boundary surfaces STF support surface B STF Width of the support surface B BF Width of the boundary surfaces

Claims

[1] Single-lip drill comprising a drill head (11), wherein the drill head (11) comprises two replaceable guide strips (27), a bead and a cooling lubricant channel (43), wherein the drill head (11) has two recesses (41) for receiving the guide strips (27), wherein the recesses (41) have two parallel side surfaces (SF) and a base surface (GF), and wherein the cooling lubricant channel (41) opens into a front side or tip (19) of the drill head (11), characterized by that a width (BGF) of the base area (GF) is at least 30% smaller than a distance (DSF) of the side surfaces (SF). [2] Single-lip drill comprising a drill head (11), wherein the drill head (11) comprises two replaceable guide strips (27), a bead and a cooling lubricant channel (43), wherein the drill head (11) has two recesses (41) for receiving the guide strips (27), wherein the recesses (41) have two parallel side surfaces (SF) and a base surface (GF), and wherein the cooling lubricant channel (43) opens into an end face (19) of the drill head (11), characterized by that a width (B SF ) of the side surfaces (SF) is at least 30% smaller than a depth of the recess (41). [3] Single-lip drill according to one of the preceding claims, characterized by that at least one flat connecting surface (45) is provided between a side surface (SF) and the base surface (GF). [4] Single-lip drill according to claim 3, characterized by that at least one step is provided between the side surfaces (SF) and the base surface (GF). [5] Single-lip drill according to one of the preceding claims, characterized by that at least a singly curved connecting surface (49) is provided between a side surface (SF) and the base surface (GF). [6] Single-lip drill according to claim 5, characterized by that the curved connecting surface (49) is concavely or convexly curved. [7] Single-lip drill according to one of the preceding claims, characterized by that the recesses (41) extend substantially parallel to a rotation axis (23) of the single-lip drill (1). [8] Single-lip drill according to one of the preceding claims, characterized by that the recesses (41) are arranged offset from one another in the circumferential direction by an angle β which is greater than 100° and less than 118°. [9] Single-lip drill according to one of claims 3 to 7, characterized bythat a center point (M) of the cooling lubricant channel (43) lies in the middle between the flat connecting surfaces (45) or in the middle between the at least singly curved connecting surfaces (49) of the recesses (41). [10] Single-lip drill according to one of the preceding claims, characterized by that the center point (M) of the cooling lubricant channel (43) lies in the middle between a (cylindrical) outer surface of the drill head (11) and a plate seat (35) of an exchangeable cutting plate (25) of the drill head (11). [11] Single-lip drill according to one of the preceding claims, characterized by that the bead is delimited by a chip surface (15) and a wall (19), that the chip surface (15) and the wall (19) enclose an angle (α) and that the angle (α) is between 105° and 125°, preferably equal to 115°. [12] Guide rail for a single-lip drill (1) comprising a guide surface (39), two lateral boundary surfaces (BF) and at least one support surface (STF), wherein the lateral boundary surfaces (BF) run parallel to one another and the boundary surfaces (BF) and the support surface (STF) are arranged at right angles to one another, characterized by that a width (B STF ) of the support surface (STF) is at least 30% smaller than a distance (D BF ) of the boundary surfaces (BF). [13] Guide rail for a single-lip drill (1) comprising a guide surface (39), two parallel lateral boundary surfaces (BF) and at least one support surface (STF), wherein the boundary surfaces (BF) and the support surface (STF) are arranged at right angles to each other, characterized by that a width (B STF ) of the boundary surfaces (BF) is at least 30% smaller than a thickness (D) of the guide strip (39). [14] Guide rail according to claim 12 or 13, characterized by that at least one flat connecting surface (47) is provided between the boundary surfaces (BF) and the support surface (STF). [15] Guide rail according to claim 14, characterized by that at least one step is provided between the boundary surfaces (BF) and the support surface (STF). [16] Guide rail according to claim 12 or 13, characterized by that at least one curved connecting surface (51) is provided between the boundary surfaces (BF) and the support surface (STF). [17] Guide rail according to one of the preceding claims, characterized by that it is made of hard metal. [18] Guide rail according to one of the preceding claims, characterized by that it is provided with a hard coating.

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