FR2521468A1 - FOREST - Google Patents

Abstract

THE INVENTION RELATES TO A DRILL WHOSE HEAD 13 SHOWS AT LEAST THREE MAIN EDGES 14, 15, 16, DISTRIBUTED AT PRACTICALLY EQUAL PERIPHERAL ANGULAR DISTANCES, AND CORRESPONDING TO CENTRAL EDGES 24, 25, 26 JOINING THE CENTRAL AXIS 27. EACH CENTRAL EDGE CONTAINS AN INTERNAL EDGE 34, 35, 36 AND AN EXTERNAL EDGE 44, 45, 46 FORMING AT THEIR POINT MEETING A PROJECTING AXIAL POINT 28, 29, 30. ALL THE POINTS ARE LOCATED AT EQUAL RADIAL DISTANCES FROM THE AXIS CENTRAL AND AT THE SAME HEIGHT IN THE AXIAL SENSE. GROOVES 17, 18, 19 FROM THE HEAD ARE ALSO PROVIDED. AT LEAST ONE SECTION OF EACH CENTRAL AND OR MAIN EDGE, EXTENDING ESSENTIALLY AT LEAST IN THE RADIAL DIRECTION, IS PLACED IN THE DIRECTION OF CUT, THAT IS, IN THE DIRECTION OF ROTATION, BEFORE THE CENTER OF THE HEAD. EACH GROOVE HAS THE SHAPE OF A HELICOIDAL GROOVE. THE TOOL ALLOWS HIGH PRECISIONS OF POSITION, SHAPE AND QUALITY OF BALLS TO BE OBTAINED AND IS INDIFFERENTLY ADAPTED TO DISCONTINUOUS, INTERMEDIATE AND CONTINUOUS CHIP MATERIALS.

Description

Forest

  The present invention relates to a drill bit whose head

  te at least three main cutting edges, distributed at

  practically equal peripheral angular forces, and

  corresponding to central cutting edges joining the central axis

  tral, each central cutting edge having an inner cutting edge

  dull and an external cutting edge, respectively forming an

  obtuse gle and an acute angle with the central axis and axial io points projecting at their meeting point, these points being at equal radial distances from the axis

  central and at the same height in the axial direction, and which pre-

  feel grooves extending from the head.

  In a known device of this type (DE-GM 77 10 873), each

  that main cutting edge and corresponding central cutting edge have a cutting angle of 00 Each of these cutting edges

  lies in a diametral plane passing through the center of the

  til The grooves are formed by straight grooves

  parallel to the central axis and joining the drill shank.

  This type of drill is entirely suitable for machining material

  rials with discontinuous chips, especially foundry materials.

  For materials with higher toughness, the tool presents

  te risks of breakage, due to defective chip removal and evacuation The advantage of this type of tool is

  however in the fact that the spikes allow a per-

  direct material drilling, without centering hole or device

  particular auxiliary, without risk of off-center and / or rup-

  ture; all the points arriving in effect simultaneously in contact with the workpiece in the advance movement of the tool, the load obtained in the radial direction is symmetrical from the initial phase of drilling, because each point attacking the workpiece forms a support for the other tip In this phase

  initial drilling, all points allow

  ser in the workpiece a circular V-shaped groove corresponding to the geometry of the cutting edges in the zone of the points and concentric with the central axis With the progressive attack of the points-on the part, this groove becomes more and more

  wide to reach the nominal diameter dimension L'es tran-

  central edges being slightly lowered in relation to the main cutting edges, the distribution obtained in this

  zone allows to obtain chips of moderate width.

  This type of drill having the advantages described, as well as a high concentricity and a dimensional accuracy, of shape and position of the hole to be drilled, lends itself to all materials with discontinuous chips. tougher materials, especially steel,

  causes the drill to rupture and results in failure.

  The present invention aims to create a drill of the above type.

  describes how, while presenting the advantages

  cited, offers much wider employment opportunities

  ges and lends itself, with the same advantages and a high stability, not only to the machining of materials with discontinuous chips, but also to that of other materials,

including continuous chips.

  According to an essential characteristic of the invention, a

  at least section of the central and / or main cutting edge,

  tending essentially at least in the radial direction, is placed in the cutting direction, that is to say in the direction of rotation of the tool, before the center of the head, and each

  groove has the shape of a helical groove.

  Advantageous developments of the present invention are

  given in claims 2 to 6.

  The helical grooves are already known, on helical drills for example. We know that these drills present disadvantageous conditions on the transverse cutting edge.

  sal The cutting nail being greater than 90, it is im-

  possible to speak of cutting, but rather of grinding or

  other As soon as the transverse cutting edge, at the exit of the

  ret, no longer compresses the material, the pin retaining the form

  ret returns to its original position The feed rate is modified in fits and starts The drill can catch and break due to excessive force These problems are not eliminated, even when the transverse cutting edge of the drill is blunt for stubborn materials These facts are known for

  be responsible for the poor quality of the drills obtained

  bare by helical drills In addition, from certain

  some drilling diameters, it is essential to

  der to a pre-centering using small holes.

  The drill according to the present invention combines the advantages

  stages of a self-centering tool, using the tran

  central edges, and in particular their tips, and a twist drill, in the measurement or removal and evacuation

  shavings are improved by the helical shape of the king-

  nures The geometry of the main cutting edges and corresponding central cutting edges also makes it possible to obtain a particular constitution and shape of the chips. The chip formed in the area of the central cutting edge thus has a specific geometry and shape. The chip formed in the area of each main cutting edge, extending outward

  the corresponding central cutting edge, moreover, has a form

  me and an equally specific geometry, this chip being subjected to a deformation linked to a compression which reduces

  its dimension relative to that of the groove, and which

  puts to obtain a satisfactory flow and evacuation

  Because of this formation and evacuation par-

  chips, the drill adapts, while retaining

  In view of the aforementioned advantages, when machining materials such as

  naces and steel, therefore of disconnected chip materials

continuous, intermediate and continuous.

  Other advantages and characteristics of the invention are-

  will be better understood using the detailed description

  below, and attached drawings which represent:

  Figure 1: a schematic side view of the lower part

  of a three-edged drill, only two of which are shown in the drawing plane for clarity, Figure 2: a front view of the lower end of the drill head, Figure 3: a schematic view, practically similar to her

  of figure 2, of part of the cutting edges of a

ret in modified form.

  The drill 10 corresponding to the first example of construction

  tion of Figures 1 and 2 generally has a cylindrical and smooth rod II, used for mounting the tool, as well

  that a body 12, the head 13 of which constitutes the front end

  lower tale This head 13 comprises three main cutting edges 14, 15, 16 distributed, in an external radial position, at angular distances practically equal to, and corresponding to central cutting edges 24, 25, 26,

which join the central axis 27.

  From the side view in Figure 1, each cutting edge

  tral 24, 25, 26 consists of an internal cutting edge 34, 35, 36

  and an external cutting edge 44, 45, 46, respectively forming

  an obtuse angle and an acute angle with the central axis (27), and the meeting point of which forms the axial points 28, 29, 30 projecting downward In the view from below of the

  figure 2, and as a result of the cross-section of the material and the fa-

  this free, each point 28, 29, 30 is represented by a

section of an inscribed circle.

  The three points 28, 29 30 being located at the same distance

  this radial of the central axis 27 and at the same height in the axial direction, their application to the face of a part is simultaneous.

  Three grooves 17, 18, 19 start from the head 13.

  Each groove 17, 18, 19 has the particular shape of a rai-

  helical, basically known by the drill bit

  licoldal If the clearance angle is generally between 25 and 35, it nevertheless depends on the material of the

workpiece.

  In the cutting direction following arrow 20, -a section at

  less than each central cutting edge 24, 25, 26 and / or main

  pal 14, 15, 16, extending in the radial direction, is placed before the center of the head 13 According to FIG. 2, this center coincides with the edge limiting the free face, in

  rear of the main and central cutting edges This edge

  You can use it as a reference line.

  In the construction example shown in Figures 1 and 2, each main cutting edge 14, 15, 16 is placed before the center, the distance from a diametrical plane passing through this center being approximately 0.4 to 1.2 mm In Figure 2, the average distance is shown

  only for main cutting edge 14 with the letter d.

  In the first example of construction, the arrangement of the central cutting edges 24, 25, 26 is also such that

  their internal cutting edges 34 to 36 and external cutting edges 44 to 46

  pectives lie in a radial plane, before the center e-

  also Each central cutting edge 24, 25, 26 forms with an diametral plane passing through the center an angle of 270 to 320 In FIG. 2, this angle is represented by the letter 0 <for the central cutting edge 24 This angle is 28 for example According to this same figure, each central cutting edge 24, 25, 26 is extended, at the radial end of its external cutting edge 44, 45, 46, by the main arcuate cutting edge 14,

  , 16, corresponding to it in a radial position ex-

  dull. Because of this particular conformation, the drill

  can be used to drill almost any material

  materials, discontinuous chips, such as cast iron, and co-

  continuous skins, including steel Centering points 28, 29, 30 allow the drill to adapt perfectly to drilling operations Pre-holes are unnecessary During operations, the points 28, 29, 30 ensure centering automatic drilling This results in an extremely high dimension and shape of the bore, therefore a very precise gauge, roundness and linearity of the drilling, as well as a satisfactory surface condition of the wall of the hole These advantages are mainly due to the particular shapes of the main cutting edges 14 to

  16 and central 24 to 26, ensuring different functions.

  During the operation, the central cutting edges 24 to 26

  produce a chip of corresponding shape and width.

  The corresponding central cutting edges 14, 15, 16 pro-

  on the other hand, produce a specific chip of another shape and width, each form of chip depending on the geometry of the cutting edges. In the area of the main cutting edges 14, 15, 16, the chip is subjected to a deformation, namely compression. products are therefore smaller than the cross-section of the corresponding groove 17, 18, 19 They can therefore be removed without difficulty by these grooves 17, 18, 19 Besides the shape of the central cutting edges 24, 25, 26

  and the function of tips 28, 29, 30, the parti-

  the various shavings and the satisfactory evacuation obtained contribute to the extremely high precision of the operations carried out using this drill 10, concentricity

  perfect machine side and high precision of the holes to be drilled

  cer, precision of form and holding of the dimensions in particular This same

  drill bit 10 guarantees at the same time stability and duration of use.

  high bends, without any risk of deterioration, or even

me of destruction.

  The construction example shown in Figure 3 includes

  has two variants In the variant illustrated by the dashed line, the external cutting edge 144 does not

  does not lie in the radial extension of the cutting edge

  ne 134, maos before the diametrical plane passing through the center. At their meeting point, the internal 134 and external cutting edges 144 form a point. The latter is located, by

  example, on the radial plane passing through the tip of the

  edges As in the first example of construction, the main cutting edge 114 is extended in an arc, forming a

  concavity, by the external cutting edge 144.

  In the variant shown in Figure 3 in contiguous line

  naked, the central cutting edge 224 is designed exactly as in the first example of FIG. 1, that is to say that the external cutting edge is located in the radial extension of the

  internal cutting edge, forming an angle od before the center.

  The main cutting edge 214, which is extended by the cutting edge

  central edge 224, is rectilinear and practically pardlla-

  the diametrically passing through the center.

Claims (4)

Claims.   1 Drill whose head (13) has at least three main cutting edges (14, 15, 16), distributed at substantially equal peripheral angular distances, and corresponding to central cutting edges (24, 25, 26) joining the central axis ( 27), each central cutting edge (24, 25, 26) comprising an internal cutting edge (34, 35, 36) and an external cutting edge (44,   , 46), respectively forming an obtuse angle and an an-   acute gle with the central axis (27) and projecting axial points (28, 29, 30) at their meeting point, these points being located at equal radial distances from the central axis (27) and the same height in the   axial direction, and which has grooves extending from the head   te (13), characterized in that at least one section of the central (24, 25, 26) and / or main (14, 15, 16) cutting edge, extending essentially at least in the radial direction,   is placed in the cutting direction (arrow 20) before the center   be of the head (13), and in that each groove (17, 18,   19) has the shape of a helical groove.   2 drill according to claim 1, characterized in that   the internal cutting edge (34, 35, 36) at least of each cutting edge   central edge (24, 25, 26) is placed before the center.   3 Drill according to one of claims 1 and 2, character-   laughed in that the internal cutting edges (34, 35, 36) and ex-   dull (44, 45, 46) corresponding lie on a plane radial, before the center.   4 drill according to any one of claims 1 to 3,   characterized in that the main cutting edges (14, 15, 16), also placed before the center, have an average spacing (d) of 0.4 to 1.2 mm relative to a diametral plane passing through this center.   Drill according to any one of Claims 1 to 4,   characterized in that the section of each cutting edge cen-   tral (24, 25, 26) placed before the center, from the cutting edge   dull (34, 35, '36) in particular and the outer cutting edge (44, 46) located on the same diametral plane, forms an angle (d L) of 27 to 32 with a diametral plane passing through the center. 6 drill according to claim 5, characterized in that the angle (i) is equal to d 28.