EP3209442A1

EP3209442A1 - Twist drill and production method

Info

Publication number: EP3209442A1
Application number: EP15781928.5A
Authority: EP
Inventors: Corinna Achleitner; Mark Winkler; Guenter Domani; Carsten Peters
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 2014-10-23
Filing date: 2015-10-20
Publication date: 2017-08-30
Also published as: CA2964814A1; CA2964814C; WO2016062683A1; US20170348760A1; US10252321B2; EP3012039A1; CN107073598A

Abstract

A method for producing a twist drill 1 has the following steps. A blank 27 is shaped to form a semi-finished product 34. The semi-finished product 34 is formed from a core 38, coaxial with the drill axis 2, having a radius 51 and a number of webs 39, arranged on the core 38, having a height 40. The semi-finished product 34 has a constant cross section along the drill axis 2. The webs 39 have a first portion 42 which adjoins the core 38 and in which a width 44 of the web 39 remains constant or decreases in the circumferential direction 11 with increasing radial distance from the drill axis 2. The webs 39 have a second portion 43 which adjoins the first portion 42 and in which the width 44 of the web increases in the circumferential direction 11 with increasing radial distance from the drill axis 2. The webs 39 of the semi-finished product are shaped into helical segments using a plurality of rolling tools that annularly enclose the semi-finished product 34 and roll on the webs 39 along the drill axis 2. The rolling tools 31 have teeth 48 that are inclined with respect to the drill axis 2. A height 20 of the helical segments is less than the height 40 of the webs 39. Helical segments formed from adjacent webs 39 are in contact with one another in a closing fold 26. The invention also relates to a twist drill.

Description

Helical drill and manufacturing process

FIELD OF THE INVENTION

The present invention relates to a manufacturing method for a twist drill and a twist drill having a plurality of spiral webs.

DISCLOSURE OF THE INVENTION

The production method for a twist drill according to the invention has the following steps. A blank is transformed into a halfling. The halfling is formed of a core having a radius coaxial with the drill axis and a number of ridges arranged on the core with a height. The halfling has a constant cross section along the drill axis. The webs have a first portion adjacent to the core and in which a width of the web in the circumferential direction remains the same or decreases with increasing radial distance to the drill axis. The webs have a second portion adjacent to the first portion and in which the width of the web increases in the circumferential direction with increasing radial distance to the drill axis. The webs of the halfling are formed into helical segments with a plurality of rolling molds surrounding the halfling and rolling on the webs along the drill axis. The rolling tools have inclined teeth relative to the drill axis. A height of the helical segments is less than the height of the webs. Helical segments formed from adjacent lands contact one another in a closing fold.

The forming of the blank takes place in at least two stages. During a first stage, the material of the preferably cylindrical blank is pushed together from an angular range to webs. The resulting webs have a mushroom-shaped form whose outer head contains a large amount of material. During a second stage, the web is longitudinally rolled. The material from the head is guided by the rolling tools back into the previously disclosed Wnkelbereich pushed back. The inclined teeth push the material on the one hand and prevent material flow in the later spiral turns. The material thereby accumulates in the helical segments. Adjacent rolling tools push both parts of their material into a curved region lying between the webs to be formed. The two helical segments collide in the circumferential direction and form a continuous helix. In the helix, a closing fold remains, at which the segments abut each other.

The closing folds can lie in planes which contain the drill axis and are arranged centrally between adjacent webs. The material flow of both webs in and against a circumferential direction is approximately the same due to a symmetrical design of the rolling tools.

The head of the web preferably contains much material that can be redistributed during rolling of the helical segments. An embodiment provides that in the cross section, a surface of the first portion is smaller than a surface of the second portion.

The head projects radially beyond the helix to be produced so that the rolling tools can redistribute material over the entire length of the web into the curved regions between the webs. The height of the webs is preferably at least 20% greater and at most 100% greater than the height of the helical segments.

An embodiment provides that the number of webs is equal to or greater than the number of spiral spines. Preferably, the number is the same.

An inventive twist drill has a drill head and a helix. The helix includes a cylindrical core defining a drill axis and a number of helical helix webs connected to the core. The spiral webs are each formed of a plurality of segments which contact each other along parallel to the drill axis extending closing folds. The closing folds may lie in a plane containing the drill axis. The core is commonly understood to be a helix, the largest cylinder that can be inscribed in the helix. An embodiment provides that a height of the closing fold is equal to the height of the spiral web. The closing fold begins at the cylindrical core.

One embodiment provides that segments of a first of two groups of the segments are delimited by an edge pointing in the direction of rotation of the helix drill and one of the closing folds, and segments of a second of the two groups of the segments by an edge facing in the direction of rotation and one of the closing folds are limited. BRIEF DESCRIPTION OF THE FIGURES

The following description explains the invention with reference to exemplary embodiments and figures. In the figures show:

Fig. 1 a helical drill

2 shows a cross section through a helix of the helical drill in the plane II-II. FIG. 3 shows a cross section through a helix of the helix drill in the plane III-III. FIG. 4 shows a cross section through a helix of the helical drill in the plane IV-IV FIG. 5, 6 a rolling stand

Fig. 7 shows a halfling in cross section Fig. 8, 9 a rolling stand Same or functionally identical elements are indicated by the same reference numerals in the figures, unless stated otherwise.

EMBODIMENTS OF THE INVENTION FIG. 1 schematically shows, in simplified form, an exemplary helical drill 1. The helical drill 1 has, along a drill axis 2, successively a drill head 3, a helical coil 4 and an insertion end 5.

The illustrated twist drill 1 is designed for the processing of rock, in particular for a rotary movement superimposed Meißeltätigkeit. The drill head 3 has four chisel edges 7 which point in the direction of impact 6. The chisel edges 7 are each formed as a crossing line of a surface leading in the direction of rotation of the helical drill 1 and a trailing surface which are both inclined relative to the drill axis 2 and inclined relative to each other by at least 60 degrees. The chisel edges 7 extend substantially in the radial direction, for example starting from a tip 8 of the drill head 3 to an edge of the drill head 3, where the chisel edges 7 are preferably set back in the direction of impact 6 with respect to the tip 8. An inclination of the chisel edges 7 against the Drill axis 2 may be constant in the radial direction or lower in the region of the tip 8 than at the edge. In particular, the chisel edge 7 can run perpendicular to the drill axis 2 at the edge. To the pointing in the direction of impact 6 chisel edges 7 is followed at the edge of the drill head 3, a demolition edge 9, which is parallel to the drill axis 2. The demolition edge 9 is preferably radially beyond the helix 4 addition. The drill head 3 is provided at its periphery with parallel to the drill axis 2 extending discharge channels 10, along which the drill dust can be transported from the well. The discharge channels 10 are arranged in the circumferential direction 11 between the chisel edges 7. The drill head 3 is preferably a continuous sintered cemented carbide body containing, for example, tungsten carbide and a metallic binder. The illustrated drill head 3 has two pairs of differently shaped chisel edges, of which the chisel edges forming the point 8 are referred to as main cutting edges and the other pair as secondary cutting edges. Instead of four, the bit body may also have two, eg only the major cutting edges, or three or more than four cutting edges.

The helix 4 is composed of a massive cylindrical helical core 12 and four helix webs 13 that wind around the helix core 12. The spiral core 12 and the spiral webs 13 are connected to each other without seam. A division of the helix 4 in spiral core 12 and spiral webs 13 is based on their characteristic shapes. The spiral webs 13 define the entire surface of the helix 4. The spiral webs 13 have a rising from a helical base 14 to a helical spine 15 in the circumferential direction 11 rising edge 16 and circumferentially 11 falling edge 17. The distance of the helical bottom 14 to the drill axis 2 is the Inner radius 18 of the helix 4 and the distance of the helical spine 15 to the drill axis 2 is the outer radius 19 of the helix 4. The cylinder with the inner radius 18, ie the largest inscribable in the helix 4 cylinder is the helical core 12. The volumes between the surface and the spiral core 12 are assigned to the spiral webs 13. A height 20 of the spiral webs 13 is the difference of the outer radius 19 and the inner radius 18 of the helix. The helix 4 has three, four, five or six spiral webs 13. The helical webs 13 is preferably formed identically. For example, in the case of four spiral webs 13, two spiral webs may have a smaller height than the other two spiral webs 13. The spiral webs 13 are preferably distributed uniformly around the drill axis 2. A Wnkelabstand 21 of the spiral webs 13, measured in a direction perpendicular to the drill axis 2 cross section (Fig. 2), the number of spiral webs 13 corresponding fraction of the full circle, for example, 90 degrees. The helix 4 has a ganzzählige rotational symmetry, eg vierzählige rotational symmetry. A pitch 22 of the helix 4 is the axial distance two adjacent spiral webs 13, measured in a parallel to the drill axis 2 longitudinal section. The pitch 22 is preferably constant. The coil 4 is correspondingly along the drill axis 2 periodically. Fig. 2 shows a first cross-section through the helix 4, Fig. 3 shows a second cross-section offset approximately one-eighth of the pitch 22 to the first cross-section, and Fig. 4 shows a third cross-section about half the pitch 22 to the first Offset cross-section. The exemplary coil 4 rotates about 12 degrees from the first cross section to the second cross section, 45 degrees from the first cross section to the third cross section.

The spiral webs 13 are divided several times into segments 23, 24, 25 both in the circumferential direction 11 and along the drill axis 2. An exemplary segment 23 is hatched in Fig. 1 highlighted. The segments 23, 24, 25 are identical in the exemplary drill. The segments 23 adjoin one another in the circumferential direction 11 and along the drill axis 2 to each other. The segments 23, 25 adjacent to the drill axis 2 are assigned to different spiral webs 13. The segments 23 are delimited along the drill axis 2 by the helical base 14. The division of the spiral webs 13 into the segments 23, 24 takes place in the circumferential direction 11 by closing folds 26, which extend over the entire length of the coil 4 and the entire height 20 of the coil webs 13. The closing folds 26 are substantially planar and lie in four planes E. The planes E are parallel to the drill axis 2 and may optionally contain or have a distance from the drill axis 2 which is significantly less than the inner radius 18, e.g. less than 10% of the inner radius 18. The planes E are under the same curvature, e.g. perpendicular to each other.

The adjacent segments 23, 24 are in contact with each other in the closure fold 26. The closure fold 26 represents an interruption in the material texture from one of the segments 23 to the adjacent segment 24. However, the two segments 23 are mechanically in contact, i. touch each other. There is no air gap between the segments 23, 24. The closing fold 26 can be made visible, for example, in a cross-section transverse to the drill axis 2. For example, by etching the cut, the closing fold 26 can be emphasized.

The manufacturing method described below for the twist drill 1 is mainly concerned with the production of the helix 4 Shanking 5 and the manufacture or attachment of the drill head 3 are only preferred examples.

Fig. 5, 6 show schematically a processing step of a blank 27 in longitudinal section V-V or cross-section Vl-Vl. The blank 27 is, for example, a cylindrical wire having a radius 29 which is constant along the blank axis 28. The cross section of the blank 27 is preferably circular for ease of procurement, but may also have another approximately circular shape, e.g. polygonal, oval. The illustrated manufacturing method elongates the blank 27 to a desired length, e.g. the length of the helix 4 or the length of the helical drill 1 including the insertion end 5. In a preferred variant, the helix 4 is first formed in the blank 27 and subsequently cut the helix 4 to the desired length. A first forming stage forms a plurality of longitudinal grooves 30 in the blank 27. For example, the four longitudinal grooves 30 are rolled into the blank 27 by a rolling mill with four rotating rolling tools 31. The rolling is preferably carried out with a longitudinal roller, in which the blank 27 is inserted in a driving direction 32 parallel to the blank axis 28 between the rolling tools 31. The rolling tools 31 rotate about axes 33 which are perpendicular to the advancing direction 32. The longitudinal grooves 30 have a length of the blank axis 28 constant cross-section. The longitudinal grooves 30 preferably have an identical shape and are distributed uniformly around the blank axis 28. The halfling 34 resulting from the blank 27 has a symmetry about the blank axis 28 corresponding to the cross-section of fourfold symmetry.

Fig. 7 shows a cross-section through the halfling 34. The outline of the original blank 27 is shown dotted. The longitudinal groove 30 is open in a direction 35 perpendicular to the drill axis 2 out. The longitudinal groove 30 expands continuously with increasing distance from the drill axis 2. The longitudinal groove 30 has a bottom 36 and two opposite walls 37. The bottom 36 may be circular or elliptically curved as shown, or planar in a central region. The walls 37 are largely flat. The exemplary walls 37 are parallel to each other and to the direction 35. The walls 37 may also be slightly inclined to each other, with the distance from the blank axis 28 from each other.

The halfling 34 consists of a cylindrical core 38 and four webs 39. The radius 51 of the core 38 is equal to the distance of the bottom 36 of the longitudinal grooves 30 to the Blanksachse 28. The webs 39 are formed by the forming. A height 40 of the webs 39 is equal to the difference of the radius 51 to the outer radius 41 of the half ring 34th

The webs 39 preferably have the same shape, which forms between the longitudinal grooves 30. The shape of the webs 39 is mushroom or trumpet-shaped. The web 39 has an inner portion 42 which is adjacent to the core 38, and an outer portion 43 which is adjacent to the side facing away from the core 38 side of the inner portion 42. The web 39 has a width 44 dependent on the distance to the blank axis 28. The width 44 denotes the dimension in the circumferential direction 11 in a length dimension, i. the distance between two points lying on opposite surfaces, which are in a plane perpendicular to the blank axis 28 and at the same distance from the blank axis 28. The width 44 decreases in the inner portion 42 with increasing distance to the blank axis 28 continuously. The web 39 has a waist 45, i. thinnest place. The inner portion 42 terminates at the waist 45. The outer portion 43 is the remainder of the web 39 outside the waist 45, i. at a greater distance to the blank axis 28 as the waist 45. The width 44 increases in the outer portion 43 adjacent to the waist 45. The maximum width of the outer portion 43 is 150% to 250% of the width 44 of the waist 45. The distance of the waist 45 to the blank axis 28 is between 80% and 125% of the outer radius 19 of the helix 4 to be produced.

The halfling 34 provided with the webs 39 is fed to a second stand with four second rolling tools 46 (FIGS. 8, 9). The second frame rolls the webs 39 by longitudinal rollers in continuous, shown four, spiral webs 13 to. The rotation or pivot axes of the rolling tools 46 are perpendicular to the feed direction and drill axis 2 of the half ring 34. The second rolling tools 46 are preferably the same and arranged around the drill axis 2, preferably at equidistant angles. Each of the rolling tools 46 processes a different angle section 47 of the halfling 34. The rolling tools 46 adjacent in the circumferential direction 11 preferably contact one another such that the rolling surfaces form a closed ring around the drill axis 2 of the halfling 34. An axial portion of the halfling 34 is simultaneously deformed from all sides and the axial portion shifts continuously along the drill axis 2.

The halfling 34 may be fed to the second framework with a defined orientation of curvature. In the illustrated embodiment, the second stand is rotated 45 degrees from the first stand. The webs 39 are each centrally or approximately centrally to the rolling surfaces. The second rolling tool 46 thus forms one of the webs 39. Accordingly, the number of second rolling tools 46 is equal to the number of lands 39. The rolling tools 46 have a shape analogous to a helical gear with a plurality of teeth 48. A head line 50 of the teeth 48 is inclined relative to the axis of rotation 49 of the rolling tools 46 by one an inclination angle. The inclination angle is between 35 degrees and 60 degrees and is selected according to the desired spiral pitch. Deviating from a prismatic shape, the teeth 48 have a circularly concave curved head line 50. The curvature is approximately equal to the curvature of the spiral base 14 to be produced. A height of the teeth 48 decreases monotonically along the axis of rotation from the edge towards the center and then until monotonically towards the edge. The teeth 48 preferably contact the core 12 of the halfling 34 during rolling without being deformed. The second rolling tool 46 mainly shapes the material in the outer portion 43 of the lands 39.

Claims

Method for producing a helical drill (1) with a helix (4) which has a number (N) of spiral webs (13) running around a drill axis (2) in a spiral pitch, comprising the steps of:

Forming a blank (27) into a halfling (34) formed by a core (38) with a radius (51) coaxial with the drill axis (2) and a number of webs (39) arranged on the core (38) a height (40), along the drill axis (2) has a constant cross section, wherein the webs (39) adjacent to the core (38) has a first portion (42) in which a width (44) of the web (39) in Circumferential direction (11) with increasing radial distance to the drill axis (2) remains the same or decrease, and adjacent to the first portion (42) has a second portion (43) in which the width (44) of the web in the circumferential direction (1 1) increases with increasing radial distance to the drill axis (2),

Forming of the webs (39) into helical segments with a plurality of halfling (34) annular and along the drill axis (2) rolling on the webs (39) rolling tools, which relative to the drill axis (2) inclined teeth (48), wherein a Height (20) of the helical segments is less than the height (40) of the webs (39), and wherein from adjacent webs (39) formed helical

Segments touching each other in a closing fold (26).

2. A manufacturing method according to claim 1, characterized in that the closing folds (26) lie in planes containing the drill axis (2) and are arranged centrally between adjacent webs (39).

3. A manufacturing method according to claim 1 or 2, characterized in that in the cross section, a surface of the first portion (42) is smaller than a surface of the second portion (43).

4. Manufacturing method according to one of the preceding claims, characterized in that the height (40) of the webs (39) is at least 20% larger and at most 100% greater than the height (20) of the helical segments.

5. Manufacturing method according to one of the preceding claims, characterized in that the number of webs (39) is equal to or greater than the number of helical spines (15). Helical drill bit (1) having a drill head (3) and a helix (4), which has a cylindrical core (38) defining a drill axis (2) and a number of helical helix webs (13) connected to the core (38) Spiral webs (13) are each formed of a plurality of segments which contact each other along parallel to the drill axis (2) extending closing folds (26).

Helical drill (1) according to claim 6, characterized in that each of the closing folds lies in a plane containing the drill axis (2).

Helical drill (1) according to claim 6 or 7, characterized in that a height (40) of the closing fold (26) is equal to the height (40) of the spiral web.