JPS597510A - Drill - Google Patents

Abstract

PURPOSE:To reduce chip discharge resistance at deep hole boring by a method wherein chip produced at a cutting edge is rendered to curl itself with a large curvature so as to consequently realize smooth discharge of the chip in a discharge flute. CONSTITUTION:The chip 8 produced at the cutting edge 3 extends itself in a fan shape on the face of the cutting edge 3 in order to curl itself along the bottom surface of the flute 10. The tip of said chip 8 is curled sharply by means of a projection 6 and the chip 8 is discharged along the longitudinal direction of the flute 10. Concretely, the formation of the projection 6 results in curling the chip 8 in the state having larger curvature than that of the bottom of the flute 10. Consequently, the chip 8 is discharged smoothly through the flute 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drill suitable for deep hole drilling.

Recently, so-called spiral-blade drills have been proposed that improve cutting performance by eliminating the chisel part at the center of the drill and forming a cutting edge with a large curvature. Because of the large resistance encountered when passing through the shaped chip evacuation groove, good cutting performance could not be achieved in deep hole machining.

This invention was made to solve these conventional drawbacks, and the purpose of this invention is to curl the chips generated from the cutting blade into a large curvature, thereby allowing them to pass smoothly through the discharge groove. be. That is, in the present invention, the cutting edge near the outer periphery is provided with a protrusion near the front end in the direction of rotation of the drill on the bottom surface of the groove so that the curvature of the bottom surface of the chip discharge groove in the cross section in the direction perpendicular to the outer periphery is larger than the curvature of the bottom surface above it. was formed.

Embodiments of the present invention will be described below with reference to the drawings. 1st
In Figures 1 to 6, 1 is a drill shank, 2 is a tip, and the tip 2 is attached to the head of the shank 1 by brazing or other means. A cutting edge 6 is formed on each of the chips 2, and this cutting edge 6 forms a curve convex in the direction of rotation when viewed from the bottom, has a constant large curvature at the center, and becomes a straight line at the outer periphery. ing. The cutting edge 6 may have a spiral curve whose curvature increases as it approaches the center from the outer periphery. Further, the head of the shank 1 is formed into a conical shape, and each cutting edge 6 is formed point-symmetrically with respect to the center point 4 which is the apex thereof. The center point 4 may be eccentric to the extent of a manufacturing error, and the point symmetry is not strictly defined; it may be substantially point symmetrical. Furthermore, both cutting edges may be discontinuous at the center point. Note that the rake face 7 of each cutting edge 6 is formed continuously from the center to the outer periphery. Further, the protrusion 6 is formed on the cutting edge near the outer periphery so that the curvature of the bottom surface of the chip discharge groove 10 in the cross section in the direction perpendicular to the outer circumference is larger than the curvature of the bottom surface above it. In the illustrated example, the protrusion 6 has a locally small force ξ, but its vicinity may protrude over a wide range all the way to the outer periphery.

When drilling is performed with the above-mentioned drill, the chips 8 generated by the cutting blade 6 extend in a fan shape on the rake face and curl along the bottom surface of the groove 10, and the tip thereof becomes a protrusion. It is largely curled by B and discharged along the length direction of the groove 10. That is, since the protrusion 6 is formed, the chips 8 are curled to a larger curvature than the curvature of the bottom surface of the groove 10, and therefore the chips 8 are smoothly discharged from the groove 10. This prevents it from freely passing through the groove 10. Moreover, since the chips 9 extend along the bottom surface of the groove 10, their tip end hits the inner wall 80 of the machined hole, as shown by the imaginary line in FIG. For this reason, the chips 9 are rubbed against the inner wall 80 of the machined hole and the bottom wall of the groove 10 while moving up the groove 10, creating a large resistance to ejection. It was not possible to machine holes.

However, if the chip 8 is curled with a large curvature, it can easily pass through the groove 10, making it possible to easily drill deep holes, which was previously considered impossible.

As explained above, this invention has protrusions formed in the groove for curling chips generated from the external Φ exposed cutting edge, and has low chip discharge resistance, making it suitable for deep hole machining. It is particularly suitable.

[Brief explanation of the drawing]

Fig. 1 is a front view of a drill showing an embodiment of the present invention;
The figure is a side view thereof, FIG. 6 is a bottom view thereof, and FIG. 4 is a sectional view taken along the line 2--y in FIG. 2. 1...Shank, 2...Tip, 3...Cutting blade, 6
...Protrusion, 8-...Chip, 10...Chip discharge groove. Figure 1 Figure 4 Figure 2 Figure 3 Figure v Figure 4

Claims (1)

[Claims] 1. When viewed from the bottom of the drill, the pair of cutting edges have their starting ends near the center of rotation and are arranged symmetrically with respect to each other, each cutting edge has a convex curve in the direction of rotation, and the outer circumference The cutting edge curve at the center has a larger curvature than the cutting edge curve at the center, and the chip evacuation groove corresponding to each cutting edge is formed in a spiral shape on the shank, and the cutting edge near the outer periphery has a A drill characterized in that a protrusion is formed near the front end of the bottom surface of the groove in the direction of rotation of the drill so that the curvature of the bottom surface of the chip discharge groove in a cross section in the direction of cutting is larger than the curvature of the bottom surface above it.