JP2006110704A - Three-shaped clearance groove drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drill a knife edge of which is hard to break, free to use for cutting work for a long period of time and in a shape to prevent clogging of chips even when cutting speed is increased. <P>SOLUTION: This twist drill web thickness of which is 30% to 40% against a diameter of the drill and a torsion angle of which is around 30° is devised so that a cross-section shape of a clearance groove is made in such a shape of two dished grooves arranged in parallel as a figure 3 is vertically extended long and slender, a width ratio of the dished groove on the cutting blade side and the flank side is roughly 2:3, a main cutting blade having a pair of conical flanks provided with a clearance angle is formed at a head end angle of 118°, a central cutting blade and a chip pocket are provided by thinning them so that a chisel edge becomes about 10% of the diameter of the drill, a rake angle of the central cutting blade becomes -10 to -20° and a point where the central cutting blade and the main cutting blade roughly matches with a crest line where the two dished grooves make contact with each other. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

Regarding the twist shape of twist drill

  Conventional drills have been improved over the years, and their shapes are multi-branched. A drill for drilling a hole in a thick steel material is required to be strong, and it is necessary to use a thick core. Grinding by simply creating a flank at the tip of the drill increased the width of the chisel edge, resulting in a heavy thrust load during drilling and poor biting and centripetality.

  Various thinning methods have been proposed to solve the above problems. One method is called R-type without a chisel edge, but there is a drawback that the center blade is easily chipped during drilling. In addition, it was difficult to regrind and the corners of the grinder were easily worn.

  In addition, when trying to increase the cutting speed using a cemented carbide drill, the facet was clogged, that is, the drill had to be retracted to remove the facet, and then cutting had to be started again.

  Provided is a drill having a shape in which a cutting edge is hard to break, can be used for long-time cutting, is easily reground, and does not clog even when the cutting speed is increased.

Means for Solving the Invention

  The present invention has been made in view of the above problems, and in order to obtain a heavy cutting drill that is hard to break, easy to regrind, and easy to discharge a face, the shape of the core thickness, the shape of the relief groove, the shape of the relief surface and the tip pocket. As a result of intensive research for more than 10 years, the following drills were found to be optimal. In a twist drill with a core thickness of 30-40% of the drill diameter and a torsion angle of around 30 °, two countersunk grooves where the cross-sectional shape of the relief groove is elongated from the number 3 vertically The width ratio of each dish-shaped groove is approximately 2: 3, the side corresponding to the cutting edge has a ratio of 2, and the side corresponding to the flank is 3 Prepare a drill that has the same ratio, and the back clearance groove is also rotationally symmetrical.

  When this drill is ground to form a main cutting edge having a pair of conical flank surfaces with a tip angle of 118 ° and a clearance angle, the chisel edge becomes 30-40% of the drill diameter and the cutting edge A ridge line appears where two dish-shaped grooves lined up in the middle. Next, thinning is performed so that the chisel edge is approximately 10% of the drill diameter to provide a center cutting edge and a tip pocket. When grinding the chisel edge and the rear end of the flank at the same time, the rake angle of the center cutting edge is- The point where the central cutting edge and the main cutting edge are in contact with each other is set so as to be 10 ° to −20 °, and substantially coincide with the ridgeline where the two plate-shaped grooves are in contact. At this time, the lengths of the main cutting edge and the center cutting edge are substantially the same.

The invention's effect

  If you drill a hole in a thick steel material using this drill, the bite of the drill will be good, and you will be able to drill the hole without causing a shake. In this case, the facet is divided into two parts corresponding to the center cutting edge and the main cutting edge. The face corresponding to the center cutting edge is discharged into a fine cut face, and the face corresponding to the main cutting edge is discharged in a long spiral shape.

  Even if it becomes a deep hole, it is discharged out of the hole without clogging the facet, so it is possible to make a clean hole without being damaged by the facet near the entrance of the hole. Previously, since the face was clogged, the push of the drill was sometimes stopped and the face was ejected, but this need is almost eliminated and the drilling speed of the hole can be significantly increased.

  In a twist drill for heavy cutting with a core thickness of 30 to 40% of the diameter of the drill and a helix angle of around 30 °, the cross-sectional shape of the concave relief groove is a long and slender figure 3 It has a shape in which two dish-shaped grooves are arranged in parallel, and the width ratio of each dish-shaped groove is approximately 2: 3, and the side corresponding to the cutting edge corresponds to the flank in the ratio of 2 The side to be used is the ratio of 3, and the shape of the relief groove on the back side is also rotationally symmetrical and equivalent to this.

  The length of the chisel edge is approximately 10% of the diameter of the drill, a pair of center cutting edges are provided at the end of the chisel, and a main cutting edge is provided continuously from the center cutting edge. The point of contact between the center cutting edge and the main cutting edge substantially coincides with the ridgeline of the two countersunk grooves constituting the aforementioned relief groove, and the rake angle of the center cutting edge is -10 ° to The chip pocket is provided by thinning to −20 °.

  FIG. 1 shows an end view as seen from the direction of the tip of the drill when cut along a plane perpendicular to the central axis of the drill of the present invention. Therefore, this drill rotates counterclockwise as shown by an arrow in this figure to make a hole. Hereinafter, the shape of the relief groove will be described with reference to the drawings. On a straight line 2 passing through the center 1 of the drill, approximately on the circumference of the circumference 3 of the drill, the arc 5 of the groove A having a radius of about two-thirds of the drill radius having the center 4 is about the clearance groove. 3/5, on the arc, turn about 45 ° clockwise from the straight line 2 through the center of the drill, starting at about 6/5 of the entire groove as viewed from the cutting edge. Is connected to the arc 9 of the groove B having a radius of about one third of the radius of the drill having a center on the inner side 8 of the drill circumference 1 on the straight line 7, and a main cutting edge tip 10 at the tip thereof. Is slightly rounded and accommodated with a margin 11. Arc 5 and arc 9 each form a groove, but its intersection 6 becomes a ridgeline. The shape of the groove 12 on the back side is equivalent to this in terms of rotation. The core thickness of this drill is about 30% of the diameter. The twist angle of this drill is about 30 °.

  This drill is cut to form a drill tip, the mold of which is shown in the plan view and front view of FIG. First, a pair of conical flank surfaces 14 having a clearance angle are provided so that the tip angle 13 is 118 °. The flank rear end and the chisel edge 15 are ground and thinned to obtain a center cutting edge 16. And make the chip pocket 17. The chisel edge 15 remains about 10% of the drill diameter, the rake angle of the center cutting edge 16 is -10 ° to -20 °, and the point where the main cutting edge 18 and the center cutting edge 16 intersect with each other substantially coincides with the ridgeline 6. To do.

  As described above, this drill has a ridge line in the groove, and the rake angle between the center cutting edge and the main cutting edge is different, so that the facet is divided into two and easily discharged. Drilling holes in thick steel can be performed efficiently and quickly.

  Further, even in the case of a carbide drill having a tip angle of 140 to 150 °, the groove having this shape can be applied and a high cutting speed can be realized.

The end view seen from the direction of the front-end | tip of a drill when cut | disconnecting with a surface perpendicular | vertical with respect to the central axis of the drill of this invention. The top view and front view of the front-end | tip part of the drill of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drill center 2 Straight line 3 Drill circumference 4 Groove A arc center 5 Groove A arc 6 Edge line 7 Straight line 8 Groove B arc center 9 Groove B arc 10 Main cutting edge 11 Margin 12 Back side Groove 13 Tip angle 14 Flank 15 Chisel edge 16 Center cutting edge 17 Tip pocket 18 Main cutting edge

Claims (4)

In twist drills with a twist angle of around 30 °, the concave relief groove has a shape in which the cross-sectional shape of the concave escape groove is a shape in which two countersunk grooves are arranged in parallel, such that the number 3 is elongated vertically. A drill characterized in that the shape of the groove is also rotationally symmetrical. In a twist drill for heavy cutting with a core thickness of 30 to 40% of the diameter of the drill and a helix angle of around 30 °, the cross-sectional shape of the concave relief groove is a long and slender figure 3 The drill according to claim 1, wherein two dish-shaped grooves are arranged in parallel, and the shape of the relief groove on the back side is also rotationally symmetrical and equivalent to this. The width ratio of each of the above-described relief grooves is approximately 2: 3, and the side corresponding to the cutting edge has a ratio of 2 and the side corresponding to the relief surface has a ratio of 3. The drill according to claim 1 or 2, wherein the drill is provided. The length of the chisel edge is approximately 10% of the diameter of the drill, and a pair of center cutting edges continuous to the end of the chisel are provided, and the main cutting edge continues to the outer periphery of the drill continuously to the center cutting edge. However, the point where the center cutting edge and the main cutting edge are in contact with each other substantially coincides with the ridge line where the two plate-shaped grooves constituting the above-mentioned relief groove are in contact with each other, and the center 4. The drill according to claim 2, wherein a chip pocket is provided by thinning so that a rake angle of the cutting edge is -10 [deg.] To -20 [deg.].

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