Single-lip deep hole drill

Abstract

The invention relates to a single-lip deep hole drill comprising a drill head, wherein the drill head has a drill diameter, a blade and a channel for chip removal, wherein the blade extends outwards from a rotational axis up to the perimeter of the drill head, wherein the blade has a cutting surface and wherein the channel is bordered by a chip forming surface, wherein the chip forming surface has two sections such that a first section of the chip forming surface extends in the radial direction from the rotational axis up to a first diameter, a second section of the chip forming surface connects to the first section in the radial direction, the first section is positioned above the cutting surface, and the second section is positioned nearer to the cutting surface than the first section.

Claims

1. Deep-hole gundrill comprising a drill head, the drill head having a rotational axis, a drilling diameter (D), a cutting edge, and a flute for chip removal, the cutting edge extending outwards from the or approximately from the rotational axis up to the periphery of the drill head, the cutting edge having a flat rake surface, and the flute being delimited by a chip forming surface and a wall, characterized in that the chip forming surface has, with respect to the rake surface, two different sections formed as plateaus having flat surfaces, in that a first section of the chip forming surface lies radially inside and in close proximity to the rotational axis, in that a second section of the chip forming surface lies radially outside and adjoins the first section, in that the first section of the chip forming surface and the wall of the flute transition directly into each other, in that the first section lies above the rake surface in a view of the drill head from the front, and in that the second section lies closer to the rake surface than the first section does in a view of the drill head from the front.

2. Deep-hole gundrill according to claim 1, characterized in that the second section lies at least at the same height as the rake surface.

3. Deep-hole gundrill according to claim 1, characterized in that the first section lies at least twice as far above the rake surface as the second section does.

4. Deep-hole gundrill according to claim 1, characterized in that the rotational axis of the drill head extends approximately through a rake surface.

5. Deep-hole gundrill according to claim 1, characterized in that the angle W at a step between the sections of the chip forming surface has a value of between 55 and 90.

6. Deep-hole gundrill according to claim 1, characterized in that the first diameter (D.sub.1) is approximately equal to half of the diameter (D) of the drill head.

7. Deep-hole gundrill according to claim 1, characterized in that a chip breaker having a positive rake angle is formed on the rake surface.

8. Deep-hole gundrill according to claim 1, characterized in that said deep-hole gundrill comprises a driver and a shank, and in that the flute is formed in the drill head and at least in part in the shank.

9. Deep-hole gundrill according to claim 1, characterized in that at least the drill head consists of carbide.

10. Deep-hole gundrill according to claim 1, characterized in that said deep-hole gundrill has at least one guide pad.

11. Deep-hole gundrill according to claim 1, characterized in that both the drill head and the shank consist of carbide.

12. Deep-hole gundrill according to claim 1, characterized in that the drill head is at least in part provided with a hard-material coating.

Description

DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a schematic view of a deep-hole gundrill,

(3) FIG. 2 is a view of a drill head according to the invention from above,

(4) FIG. 3 is a view of a drill head according to the invention from the front,

(5) FIG. 4 is the view according to FIG. 2 showing further dimensions, and

(6) FIG. 5 is the view according to FIG. 2 showing further dimensions.

DESCRIPTION OF THE EMBODIMENT

(7) FIG. 1 shows a deep-hole gundrill 1 schematically in somewhat simplified form. The deep-hole gundrill 1 consists of a drill head 11, a profiled shank 12, and a driver 13. By means of the driver 13, the deep-hole drill 1 is held in a deep-hole drilling machine (not shown). The drill head according to the invention can be used in the case of solid carbide tools and in the case of assembled tools in which the drill head, a profiled tube shank, and a clamping sleeve are soldered to each other.

(8) A rotational axis or the center of the drill head 11 has the reference sign 23. A flute is formed in the drill head 11 and in the profiled shank 12. The flute is delimited by a chip forming surface 15 and a wall 17.

(9) The deep-hole drill 1 according to the invention can have a drill diameter D of 6.1 mm and can be used to drill through a transmission shaft made of high-strength steel at a length of 350 mm. This task is very demanding in terms of production because high-strength steels produce long chips and are tough and, furthermore, high requirements are placed on the geometry (diameter and straightness) of the bore. In addition, in automated drilling, process reliability and therefore a short chip are extremely important.

(10) To achieve this, the chip forming surface 15 according to the invention has two sections 19 and 21. A first section 19 is arranged radially further inside, while the second section 21 is arranged radially further outside.

(11) A cooling lubricant channel 24, which is also referred to as a kidney, can be seen at the tip of the drill head 11. Said cooling lubricant channel 24 extends over the entire length of the deep-hole drill 1 in a manner known per se. Cooling lubricant is guided to the tip of the deep-hole drill 1 via the cooling lubricant channel 24. The cooling lubricant cools the drill tip and, at the same time, conveys the chips produced by the drill head 11 through the flute 15 toward the clamping sleeve 13.

(12) FIG. 2 is a schematic view of a drill head according to the invention from above. The center of the drill head or the rotational axis of the drill head 11 is provided with the reference sign 23.

(13) As already mentioned, the flute is delimited by a wall 17 and the two-part chip forming surface 15. The two sections of the chip forming surface 15 (see FIG. 1) have the reference signs 19 and 21. The first section, which is arranged radially further inside is labeled as 19. The second section, which adjoins the first section 19 outwardly in the radial direction, is labeled as 21.

(14) In a manner known per se, the cutting edge of the drill head 11 consists of an inner cutting edge 27 and an outer cutting edge 29, which form a rotational tip 31 at the point of intersection thereof. The geometry of the drill head according to the invention is independent of the shape of the tip of the drill head.

(15) In the embodiment shown as an example, the outer cutting edge 29 extends at an angle of 30 relative to an orthogonal to the rotational axis 23. The inner cutting edge 29 extends at an angle of 20 relative to an orthogonal to the rotational axis 23. In short, the example involves a 30/20 nose grind.

(16) A cutting-edge tip 31, which is positioned eccentrically with respect to the rotational axis 23, is formed between the inner cutting edge 27 and the outer cutting edge 29. The diameter at which the cutting-edge tip 31 revolves when the drill head 11 according to the invention rotates about the rotational axis 23 is labeled as D.sub.2 in FIG. 2.

(17) The step between the first section 19 and the second section 21 of the chip forming surface 15 moves along a circular path about the rotational axis 23 when the drill head 11 is set into rotation. This diameter is labeled as D.sub.1 in FIG. 2.

(18) In this embodiment, the cutting-edge tip 32 is arranged at a smaller diameter than the step between the first section 19 and the second section 21. This is not necessary. It is also possible for the drill head 11 not to have a pronounced tip.

(19) The common rake surface 33 consisting of the inner cutting edge 27 and the outer cutting edge 29 has the reference sign 33. The rake surface 33 is located in a plane that extends either through or slightly below the rotational axis 23 of the drill head 11. The distance between the rake surface 33 and the rotational axis 23 must be small enough that no pin is left standing at the center of the bore.

(20) FIG. 3 is a view of the drill head 11 according to the invention from the front. The same components are provided with the same reference signs.

(21) The center of the drill head 11 or the rotational axis is shown as a point having the reference sign 23 in FIG. 3. In this view from the front, the cooling lubricant channel 24, the wall 17, and the stepped chip forming surface 15 having the sections 19 and 21 are clear.

(22) In FIG. 3, it is clear that the flat rake surface 33 extends approximately through the center or the rotational axis 23 of the drill head 11. The rake surface 33 can extend exactly through the rotational axis 23 or slightly below the rotational axis 23. In the case of a drill diameter of 6.1 mm, the rake surface 33 can extend up to 2/100 mm below the rotational axis 23.

(23) Furthermore, it is clear that the sections 19 and 21 of the chip forming surface 15 have different heights with respect to the rake surface 33. The first section 19 arranged radially inside is considerably higher than the second section 21. This height difference results in a step 25 between the two sections 19 and 21.

(24) Observing FIGS. 2 and 3 together, it is also clear that the tip of the drill head, including the flute having the wall 17 and the stepped chip forming surface 15, has only flat surfaces, which can be produced in a simple manner and with very high repeat accuracy by grinding. In other words, the drill head 11 according to the invention not only can be produced effectively and with process reliability but also can be reground relatively simply and with consistently high quality. This is especially important if the regrinding occurs not at a site of the manufacturer but at a site of the user of the deep-hole drill, because typically only relatively simple grinding devices are available there.

(25) FIGS. 4 and 5 correspond to FIGS. 2 and 3. However, more extension lines and dimensions are incorporated in FIGS. 4 and 5, at the expense of clarity.

(26) The dimensions incorporated in FIGS. 4 and 5 are largely self-explanatory. The following values have proven effective for a deep-hole drill according to the invention that has a drill diameter of 6.1 mm and is intended for making a bore in a transmission shaft made of high-strength steel:

(27) Rake angle : 0

(28) Rake surface 33: at or slightly below the center

(29) D.sub.1: 3 mm

(30) Length of the rake surface at the outer cutting edge T.sub.AS: 0.8 mm

(31) Length of the rake surface at the inner cutting edge T.sub.IS: 0.8 mm

(32) H.sub.1 (distance between the rake surface 33 or the rotational axis 23 and the first section 19 of the chip forming surface 15): 0.2 mm

(33) H.sub.2 (distance between the rake surface 33 and the second section 21 of the chip forming surface 15): 0.05 mm

(34) Radius 37 at the transition between the sections 19 and 21 of the chip forming surface: 0.05 mm

(35) Angle W at the step 25 between the sections 19 and 21 of the chip forming surface: 80

(36) In the case of different bore diameters, these values can be adapted accordingly.