JPS59142012A - Drill - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in drills, and particularly to improvements in the shape of cutting edges of drills.

Recently, in order to improve the machinability of the center of the drill,
A so-called spiral blade drill is known.

This has a spiral cutting edge formed in the center without a chisel, and this cutting edge in the center is continuous with a linear outer cutting edge formed in an extension of the helical groove. The outer cutting edge of this drill has a conical shape, but the center cutting edge has a flat surface, so the center of the cut into the rigid material cannot be determined, and center runout occurs during machining. There is a problem with it.

On the other hand, in order to improve the rigidity of the drill, particularly the machinability of deep holes, it is preferable to increase the core thickness of the drill, that is, the thickness between the bottoms of the helical grooves. Increasing the rigidity of the drill is preferable because it improves machining accuracy because core runout will not occur, especially in deep hole drilling, but as the core thickness increases, the radius of curvature of the center cutting edge of the J3 spiral blade drill increases. As the size increases, the flat surface also becomes larger, which makes it difficult to determine the center of machining for the rigid material, and the disadvantage of drilling is that not only at the start of machining, but also during machining, center runout increases. Become.

The present invention has been made in order to eliminate such conventional drawbacks, and is to increase the rigidity of the drill to improve cutting performance and to prevent core runout from occurring.

This invention provides a drill having a pair of helical grooves and a conical top surface, in which the core thickness between the bottom surfaces of the helical grooves is set to 1/4 or more of the diameter of the shank, and the core thickness is set to be 1/4 or more of the diameter of the shank. A first cutting edge that draws a convex curve in the direction of rotation when viewed from the bottom is formed point-symmetrically with respect to each other, and a second cutting edge is formed on the outer periphery at the intersection of the extension surface of the helical groove and the flank surface of the top surface of the shank. A substantially straight third cutting edge is formed between the first cutting edge and the second cutting edge, and the side shapes of the second cutting edge and the third cutting edge are substantially straight. The rotation locus circle of the first cutting blade is formed to be 115 to 1/20 of the diameter of the shank.

Embodiments of the present invention will be described below with reference to the drawings. A pair of helical grooves 2 are formed in the shank 1 of the drill, and the top portion is formed into a conical shape. A pair of first cutting edges 3 that draw a convex curve in the rotational direction near the center are formed on the top, and a second cutting edge 5 is formed at the intersection with the extended surface of the helical groove 2 and the surface 4. A third cutting edge 6 is formed to connect the first cutting edge 3 and the second cutting edge 5. This third cutting edge 6 is formed by cutting the bottom 20 of the helical groove 2.
By forming the narrow surface 61, the intersection with the flank surface 4 is formed substantially straight. The first cutting edge 3 is formed by cutting the rake face with a curvature of radius r from the inner end of the third cutting edge 6 to the center point. In addition, the back metal 7 at the rear of the flank face 4 in the rotational direction
A lubricating oil supply port 8 for cooling the cutting portion is formed in the portion.

The thickness B of the bottom portion 2011 of the helical groove 2 is 1/1/2 of the diameter.
It is set to 4 or more. Also, the diameter d of the circle drawn by the rotation locus of the first cutting edge 3 is 115 to 1 of the diameter of the shank 1.
/15 range. And the first cutting blade 3
The range of the diameter d of the circle of the rotation locus is a nearly flat surface,
The third cutting edge 6 and the second cutting edge 5 on the outside thereof are formed so that their side surfaces are substantially straight. In other words,
Part 11 of the shank is formed into a substantially conical shape by the second cutting edge 5 and the third cutting edge 6, and only the tip thereof is formed into a flat surface by the first cutting edge 3.

J3, if the core thickness B is less than 1/4 of the drill diameter, the rigidity of the drill will be insufficient, and if the diameter of the rotation locus circle of the first cutting edge 3 (1 is 115 or more than the drill diameter), core runout will occur. The prevention effect is not sufficient, and if it is less than 1/15, the cutting edge in the center will be too small and the center will not be cut well.

In the above configuration, the core thickness is very large, so the drill has high rigidity, and a cutting edge with a small radius of curvature is formed in the center instead of a chisel. It will be done. Also, the first cutting edge 3 does not form a flat surface.
range (range of diameter d) is very small, and the second cutting edge 6
Since the third cutting edge 5 is formed into a nearly conical shape, the center position during machining is easily determined, and therefore, center runout is small and good cutting can be performed. Conventionally, as the cutting edge 60 is formed with a large radius of curvature as shown by the imaginary line, the diameter of the flat surface formed on the top of the shank is extremely large, which makes it difficult to maintain a fixed center during machining. , If the center runout is raw, -ka1. picture. L tL I
c Z'! (5, Okay, Kaa.) By making the machined surface smaller and improving its rigidity, the drill can perform stable cutting, resulting in a significant improvement in cutting performance, which is especially noticeable in deep hole drilling. In addition, with the above configuration, when cutting the shank of cemented carbide or high-speed steel to form the cutting edge, the third cutting edge 6 is cut in a straight line and the inner peripheral side is slightly cut. The first and third cutting edges 3, 6 can be formed by curving the cutting edge into a curved shape, which is easier to process than the conventional cutting edge with a large radius of curvature. When the cutting edge is worn out by cutting, the relief 4 is cut to shave the rake face between the cutting blades 3 and 6, but in this case, it is not possible to precisely machine the curved shape of the rake face with the conventional cutting blade 60. Although this is difficult, in this invention most of the rake face is straight, so machining is easy.Especially in the case of a drill with a small diameter shank.
Although accurate machining of the center part is difficult, the above configuration makes machining of the center part easy and is therefore highly effective when manufacturing a thin drill.

[As explained above, this invention increases the rigidity of the drill by setting a large core thickness, and also forms a cutting edge with a small radius of curvature at the center, and an outer circumferential cut on a twisted full extension surface on the outer periphery. The two cutting edges are connected by a nearly straight cutting edge so that the top has a shape close to a conical shape, and the center run-out of the drill during cutting is small and the cutting performance is significantly improved. It is something that was given.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an embodiment of the invention, and FIG. 52 is a bottom view thereof. DESCRIPTION OF SYMBOLS 1...Shank, 2...Twisted groove, 3...1st cutting edge, 5...2nd cutting edge, 6...3rd cutting edge. Figure 1

Claims (1)

[Claims] 1. In a drill with a pair of helical grooves and a circular top surface, the core thickness between the helical groove bottoms is 17 times the diameter of the shank.
'4 or more, and near the axis center of the sink, a first cutting edge that draws a convex curve in the direction of rotation when viewed from the bottom is formed symmetrically with respect to each other, and the extension surface of the helical groove and the relief of the top surface of the shank. A second cutting edge is formed on the outer periphery by the intersection with the plane, a substantially straight third cutting edge is formed between the first cutting edge and the second cutting edge, and a third cutting edge is formed between the first cutting edge and the second cutting edge. The side shapes of the blade and the third cutting edge are formed in a substantially straight line, and the rotation locus circle of the first cutting edge is formed to be 115 to 1/15 of the diameter of the shank. Drill to do.