JPH0970706A - Twist drill, and grinding method for it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate grinding work of a flank and thining, by forming respective pairs of surfaces wherein different relief angles are formed and a pair of surfaces crossing a chisel end part and respective one-side center cutting blades respectively, and forming the respective surfaces with planes. SOLUTION: This drill is composed of a pair of center cutting blades 212 continuing from a chisel 14 and a chisel end part, a pair of first surface 1 including a pair of main cutting blades 11 continuing form the blades 12 and being formed a first relief angle; a pair of second surface 2 crossing and continuing from first surface 1 and being formed second large relief angle α2; and a pair of third surfaced 3 crossing the first and second surfaces 1 and 2, the chisel end part, and the respective one-side center cutting blades 12, and being formed of a third angle larger than the surface 2. The respective surfaces 1, 2, and 3 are formed of planes. That is, the blade 11 is formed by the first surfaces 1, which is a plane, and a groove 4, and the center cutting blade 12 is formed by the planes 1 and 3 respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tip shape of a twist drill including a solid carbide drill, and a tip suitable for a small diameter twist drill, a drill for difficult-to-cut materials such as stainless steel and a solid carbide drill coated with a hard coating. The present invention relates to a twist drill having a shape and a grinding method thereof.

[0002]

2. Description of the Related Art For improving the efficiency of drilling, the tip shape of twist drills including solid carbide drills is published on May 15, 1992 by Taiga Publishing Co., Ltd., Keizo Sakuma "Drill Reaming Manual" 46, As detailed on pages 52 to 66, conical grinding method (pages 56 and 58), two-step surface grinding method (page 55).
~ Page 57), three-step surface grinding method (three rake points
It is known to form a surface by such as (pages 56, 57) and thinning such as X-shaped thinning (page 46, etc.). As an effect of this thinning, it is known to reduce cutting resistance and improve centripetality of the drill. For this reason,
Grinding for thinning requires accuracy, but there is a problem that it cannot be ground with high accuracy. A dedicated grinding device may be used to accurately grind this thinning, but the operation was very complicated and expensive. Recently, it has become possible to accurately grind by using a borazon grindstone or a diamond grindstone with a CNC grinder, but the grinding amount of the thinning part is large, so the grinding grindstone is also damaged, and the number of processings is controlled and the shape of the grindstone is corrected. Such a problem came out.

[0003]

As an example of the conventional thinned tip shape, FIGS. 3 and 4 show a three-reiki point grinding method and the tip shape. The twist drill tip includes a chisel 21, a pair of center cutting edges 22 continuous with the chisel end, and a pair of main cutting edges 23 continuous with the chisel 21, and a pair of first clearance angles α1 are provided. The first surface 20 and the first surface 20 intersect with each other at the boundary line 27 and continue, and the first clearance angle α
A pair of second with a second clearance angle α2 greater than 1
And a third angle α3 which intersects the first surface 20, the second surface 24, the chisel end and the central cutting edge 22 of each one respectively and is larger than the second clearance angle α2. The first surface 20 and the second surface 24, which are composed of a pair of third surfaces 25, are ground by one surface 32 of the grinding wheel 30 (the outer peripheral surface or the flat end surface of the grinding wheel). Further, since the thinning portion, which is the third surface 25, has the rake surface 26 and the heel concave surface 28, it is ground using two surfaces of the grinding wheel (the outer circumference 34 of the grinding wheel and the flat end surface 32). For this reason, the grinding wheel was greatly damaged, and the shapes of the corners of the outer peripheral surface and the flat end surface were likely to collapse, necessitating correction of the grinding wheel. The object of the present invention is to solve the above-mentioned problems of the prior art, the surface and thinning can be easily and easily performed with inexpensive equipment, and the length of the chisel and the rake angle of the central cutting edge are extremely highly accurate. A twist drill with a tip shape that is suitable for solid carbide drills that are coated with a hard coating and that are drilled for difficult-to-cut materials such as stainless steel that have a tip shape whose cutting performance at the thinning part is not inferior to that of X-shaped thinning. And a grinding method thereof.

[0004]

Therefore, in the first invention of the present invention, the first invention includes a chisel and a pair of main cutting edges continuous with a pair of central cutting edges continuous with the chisel end portion. A pair of first surfaces with clearance angles and a pair of second surfaces that intersect with the first surface and have a second clearance angle that is greater than the first clearance angle; A pair of third surfaces each intersecting the first surface, the second surface, the chisel end and each one of the central cutting edges and having a third angle greater than the second clearance angle; The present invention has solved the above-mentioned problems of the prior art by providing a twist drill including a cemented carbide solid drill characterized in that each surface is formed as a flat surface and a grinding method thereof.

According to a second aspect of the present invention, the tip of the twist drill including the solid carbide drill is brought into contact with the surface of the grinding wheel which is perpendicular to the axis of the drill, and the tip of the twist drill is brought into contact with both ends of the chisel and the chisel. A pair of first surfaces including a pair of central cutting edges continuous with the part and a pair of main cutting edges continuous with the first surface, and then intersecting the first surface and continuing to the first clearance angle. Grinding a pair of second faces with a larger second clearance angle, then intersecting the second face, the chisel end and each one of the central cutting edges, respectively, and said pair of main cutting edges The virtual plane parallel to the horizontal plane is substantially horizontal, and the drill axis is inclined at a third angle larger than the second clearance angle with respect to the horizontal reference plane.
The above-mentioned problems of the prior art have been solved by providing a twist drill characterized by grinding a third surface of a pair and a grinding method therefor.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to FIGS. FIG. 1 is an explanatory view showing an embodiment of a method for grinding a twist drill of the present invention. The tip portion of the twist drill of the present invention is a flat surface 1, 2,
It is a combination of three. The first invention of the present invention includes a chisel 14, a pair of center cutting edges 12 continuous to the end of the chisel, and a pair of main cutting edges 11 continuous to the chisel 14, and a pair of first clearance angles α1 are provided. First surface 1 and a pair of second surfaces 2 which intersect the first surface 1 and are provided with a second large clearance angle α2, and the first surface 1 and the second surface 2. 2. A pair of third surfaces 3 intersecting with the chisel end and each one of the central cutting edges 12 and having a third angle α3 larger than the second surface 2, and each surface. A twist drill including a cemented carbide solid drill and a method of grinding the same, wherein 1, 2, and 3 are formed in a plane. That is, the first surface 1 which is a plane
The groove 4 forms a main cutting edge 11, and the planes 1 and 3 form a central cutting edge 12. First and second surface 1,
2 is the same as the conventional two-step surface grinding, and α1 and α2 are given as the first and second clearance angles.

A second aspect of the present invention is a drill axis line, respectively.
The first clearance angle α1 is applied to the surface grinding wheel surface 32 perpendicular to 29, and the tip of the twist drill including the solid carbide drill is brought into contact with the chisel 14 and a pair of center cutting edges 12 continuous to both ends of the chisel. And a pair of primary cutting edges 11 continuous with this, and a pair of first surfaces 1 are ground, and then a second clearance angle α2 that is larger than that and intersects the first surfaces 1 is continued. A pair of second surfaces 2 and then intersects the second surface 2, the chisel end and each one of the central cutting edges 12 respectively and an imaginary plane 11 parallel to the pair of main cutting edges 11. ′ Is made substantially horizontal, and the drill axis 29 is inclined with respect to the horizontal reference plane 13 at a third angle α3 which is larger than the second clearance angle α2, and a pair of third surfaces are ground. A twist drill and a grinding method therefor.

Preferably, as shown in the top view of the drill in FIG. 1 (c), a pair of main cutting edges 11 is provided before the third surface 3 is ground.
Virtual plane 11 'parallel to
Set it so that it is within ± 20 ° in the circumferential direction with respect to 13, and look at the horizontal reference plane 13 horizontally as shown in Fig. 1 (d) and look upward at the right main cutting edge 11 R of (c). Then, the left main cutting edge 11L of (c) can be seen downward, and the drill axis 29 is inclined with respect to the horizontal reference plane 13 as shown in FIG.
Angle .alpha.3 of .alpha.3 and feed it toward the surface 32 of the grinding wheel (the chisel length is adjusted by this feed amount) to grind one of the third surfaces 3 and set the chisel length to 1 of the drill diameter. % To 5% increases the strength of the chisel part and enables high feed processing. It goes without saying that the other third surface 3 is similarly ground.

The twist drill according to the embodiment of the present invention employs surface grinding instead of grooving grinding as a grinding method for thinning in forming the center cutting edge. Since the center cutting edge and the main cutting edge of the drill are each formed in a flat surface, the drill can be easily and easily ground with inexpensive equipment. Moreover, the chisel length can be set to 0, that is, to the point. The angle of the rake face of the center cutting edge by this surface grinding can not only be set arbitrarily, but the angle between the center cutting edge and the main cutting edge can be set by the positional relationship between the main cutting edge and the rake face of the center cutting edge. By forming the length and the rake angle of the central cutting edge with extremely high precision, a drill for difficult-to-cut materials such as stainless steel with a tip shape whose cutting performance at the thinning part is not inferior to X-shaped thinning, and a hard coating It has a tip shape suitable for coated solid carbide drills.

[0010]

As described above, in the grinding of the tip shape of the twist drill of the present invention, since only the plane of the grinding wheel is used, the grinding wheel is less damaged and can be easily and easily ground with inexpensive equipment. Also, since these surfaces can be ground with one chucking of a drill, it is easy to obtain the accuracy of the thinning portion. The angle of the rake face of the central cutting edge by this surface grinding can not only be arbitrarily set, but also the angle between the central cutting edge and the main cutting edge can be set depending on the positional relationship between the main cutting edge and the rake face of the central cutting edge. In addition, because the chisel shape of the tip of the drill can be formed with high precision, a drill for difficult-to-cut materials such as stainless steel with a tip shape whose cutting performance of the thinning part is not inferior to X-shaped thinning, and further coated with a hard coating. It has a tip shape suitable for solid carbide drills. In the present invention, the conventional three rake point grinding method is not used to grind the two sides of the corners of the grindstone, and the grinding is performed on a flat surface. Therefore, the shape of the grindstone is not deformed at an early stage due to the corner sag, and the grindstone flat surface Even if the wheel wears due to grinding, you can use a new whetstone surface by shifting the position,
Grinding with good sharpness and precision was always possible, and since the grinding heat did not rise excessively, there were few work-affected layers and the life of the cutting edge was extended. Also, since there is no heel part in the thinning part, there is no trouble of chip clogging in high feed machining.

Preferably, an imaginary plane parallel to the pair of main cutting edges is set to be substantially horizontal, or set so as to be within about ± 20 ° in the circumferential direction with respect to the horizontal reference plane, and the drill axis is set to the horizontal reference. The strength of the chisel part can be increased by inclining the pair of third surfaces with a third angle larger than the second clearance angle with respect to the surfaces and grinding the chisel length to 1% to 5% of the drill diameter. It becomes high and high feed processing becomes possible.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a method for grinding a twist drill of the present invention, (a) is a perspective view of a tip portion of the twist drill of the present invention, and (b) is a third surface 3 of the present invention. Fig. 3 (c) is a side elevational view showing the state during grinding, Fig. 3 (c) is a top view of the drill before grinding the third surface, and is a virtual plane parallel to the pair of main cutting edges 11 L and R.
The posture is set so that it is within ± 20 ° in the circumferential direction with respect to the horizontal reference plane 13 where 11 ′ is almost horizontal.
The side view which looked at from D direction is each shown.

2A is a top view of the tip portion of the twist drill of the present invention, FIG. 2B is a side view seen from the B direction in FIG. 2A, and FIG. 2C is a side view seen from the C direction in FIG. 2A. It is a figure.

FIG. 3 is an explanatory view showing a conventional three-rake point grinding method, where (a) is a perspective view of the tip of a conventional three-rake point drill, and (b) is the third surface 25 of the same figure (a). It is a side elevational view showing a state during grinding.

FIG. 4 is a side view showing a tip portion of a conventional three-rake point drill.

[Explanation of symbols]

First, second, third, first, second, third surface 11. . Main cutting edge 12. . Center cutting edge 13. . Horizontal reference plane 14． . Chisel α1, α2, α3. . First, second clearance angle, and third
Angle of

Claims (6)

[Claims] 1. A pair of first faces including a chisel and a pair of main cutting edges continuous with a pair of center cutting edges continuous with a chisel end and having a first clearance angle. , A pair of second surfaces following the first surface and having a second clearance angle greater than the first clearance angle, and a first surface, a second surface, a chisel end and A third angle that intersects each one of the central cutting edges and is larger than the second clearance angle 1
A twist drill including a cemented carbide solid drill, comprising a third surface of a pair, and each surface being formed as a flat surface. 2. A pair of first faces having a first clearance angle and a pair of first faces intersecting the first surface and having a second clearance angle larger than the first clearance angle. Second surface, first surface and second surface
Twist drill including a solid carbide drill, characterized in that a pair of third surfaces intersecting the surface of (3) and formed with a third angle larger than the second clearance angle are sequentially formed by surface grinding. Grinding method. 3. A pair of continuous chisel and both ends of the chisel by contacting the tip of the twist drill including the solid carbide drill with a first clearance angle to the surface of the grinding wheel perpendicular to the drill axis. A pair of first surfaces including a central cutting edge of the first cutting edge and a pair of main cutting edges continuous with the first cutting edge, and then intersecting the first surface and continuing to a second clearance larger than the first clearance angle. A pair of second faces is ground at an angle, and then a second plane, a chisel end, and an imaginary plane that intersects with each one of the center cutting edges and is parallel to the pair of main cutting edges. A twist drill, which is substantially horizontal, and further has a pair of third surfaces ground by inclining the drill axis at a third angle larger than the second clearance angle with respect to the horizontal reference plane. 4. A pair of continuous chisel and both ends of the chisel by contacting the tip of a twist drill including a solid carbide drill with a first clearance angle to the surface of a grinding wheel perpendicular to the drill axis. A pair of first surfaces including a central cutting edge of the first cutting edge and a pair of main cutting edges continuous with the first cutting edge, and then intersecting the first surface and continuing to a second clearance larger than the first clearance angle. A pair of second faces is ground at an angle, and then a second plane, a chisel end, and an imaginary plane that intersects with each one of the center cutting edges and is parallel to the pair of main cutting edges. A method for grinding a twist drill, which is substantially horizontal and further comprises a pair of third surfaces ground by inclining a drill axis by a third angle larger than a second clearance angle with respect to a horizontal reference surface. 5. A virtual plane parallel to the pair of main cutting edges is set so as to be within about ± 20 ° in the circumferential direction with respect to the horizontal reference plane, and the drill axis is set to the first with respect to the horizontal reference plane. Grinding a pair of third surfaces with a third angle greater than the clearance angle of 2 and setting the chisel length to 1% to 5% of the drill diameter.
The twist drill according to claim 3, wherein 6. An imaginary plane parallel to the pair of main cutting edges is set so as to be within about ± 20 ° in the circumferential direction with respect to the horizontal reference plane, and the drill axis is set with respect to the horizontal reference plane. Grinding a pair of third surfaces with a third angle greater than the clearance angle of 2 and setting the chisel length to 1% to 5% of the drill diameter.
The method for grinding a twist drill according to claim 4, wherein: