JPS6336882B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drill that has improved rigidity and improved machinability, particularly for deep hole machining.

Conventional drills have a torsional groove formed in the shank for discharging chips, but this groove width is set at a large groove width ratio of approximately 1, resulting in a decrease in torsional and bending rigidity. This has been a constraint for improving the machinability of hole machining.

The present invention has been made to solve these conventional drawbacks, and aims to increase the rigidity of the drill, thereby improving the cutting performance particularly in deep hole machining. That is, this invention:
The groove width ratio of the chip discharge groove is set within the range of 0.3 to 0.1, and the cutting edge is formed by a center cutting edge and an outer peripheral cutting edge, with a recess formed between them. . When the groove width ratio is set small in this way, various effects as described below occur. Note that when the groove width ratio is greater than 0.5, the rigidity of the drill decreases.
If it is smaller than 0.02, it will cause problems in evacuation of chips.

Embodiments of the present invention will be described below with reference to the drawings. Reference numeral 1 denotes a shank of a drill, and a pair of chips 2, 2 are attached to the tip of the shank by means such as brazing. A cutting edge 8 is formed on each of the chips 2, and the shape of the cutting edge 8 is a large curvature at the center when viewed from the bottom, and a substantially straight line at the outer periphery. And, near the tangent between the curved part and the straight part of the cutting edge 8, there is a curved surface 21 of the chip 2.
A concave portion 4 is formed along the curve, and the cutting edge 8 is separated into a curved portion and a straight portion. The pair of recesses 4, 4 may be located on the same circumference or may be located on different circumferences.

The cutting edge 8 has a central portion formed into a curved line with a large curvature in order to improve cutting performance, but the outer peripheral portion may be formed into a curved line with a small curvature instead of a straight line as shown. Further, the recess 4 for separating the cutting edge 8 into a central cutting edge and an outer peripheral cutting edge may be formed along the rake surface 22 of the chip 2.

A chip pocket 5 is formed in a portion facing the cutting edge 8 and the rake face 22, and a chip discharge groove 3 is formed in the shank in the axial direction continuously from this pocket. The bottom portion 30 of the chip discharge groove 3 is formed to become gradually shallower at the base of the shank. The chip discharge groove 3 may be formed as shown in phantom lines in FIGS. 3 and 4. Note that the top surface 6 of the shank 1 may be provided with a hole that passes through the shank to supply a cooling liquid during cutting to prevent melting away due to the heat of the raw material.

In the above configuration, the chip discharge groove 3 is formed to have a particularly narrow opening area on the outer periphery. That is, conventionally, the chip discharge groove was formed to be large as shown by the broken line 9 in FIG. 4, but in the present invention, it is formed to be particularly narrow at the outer periphery as shown by the solid line. With this configuration, the reduction in cross-sectional area due to the chip discharge grooves near the outer periphery, which greatly affects the torsional rigidity and bending rigidity of the shank, is reduced, so the torsional rigidity and bending rigidity of the shank are significantly improved. As a result, the increased torsional and bending rigidity of drills with long shank, especially for deep hole drilling, eliminates run-out of the drill core, prevents chatter, and improves the roundness of the machined surface. The accuracy of surface roughness etc. has improved.

If the ratio (α/θ) of the angle α formed by the ray from the shaft center 0 of the shank toward the open end of the chip evacuation groove to the angle θ of the non-grooved portion is expressed as the groove width ratio, in a conventional drill, this value is approximately It was 1. On the other hand, in the present invention, this value is set to 0.3 to 0.1. In the illustrated example, α/θ is approximately 0.236.

Note that when the groove width ratio is set to 0.3 or less, the torsional and bending rigidity of the shank is significantly improved, which eliminates the center runout of the drill and prevents chatter, thereby improving the roundness and surface of the machined surface. rough,
Which accuracy will be improved. Further, if the groove width ratio is 0.1 or more, chips can be discharged well. This is due to the following reasons. That is, by forming the cutting edge with a center side cutting edge and an outer peripheral side cutting edge and forming a recess between them, the chips are divided into the center side and the outer peripheral side, the center side is curled small, and the chip is curled on the outer peripheral side. The side is made into a band shape so that it can be discharged. The fact that the chips on the center side curl slightly is not limited to cutting edges with a large curvature as in the above example, but is also almost the same with straight cutting edges; therefore, it has nothing to do with the shape of the cutting edge. The above-mentioned chips are generated instead.

Further, the amount of cutting is smaller on the center side of the cutting edge than on the outer circumferential side (this is clear from the fact that the cutting edge movement locus per revolution is shorter closer to the center of rotation).
Therefore, the chips generated by the central cutting edge are curled into small pieces, and since the chips are thin, they are easily broken when fed into the narrow discharge groove and are discharged as small pieces. In addition, the chips generated by the outer peripheral cutting edge become a band-like body that gets thicker toward the outer peripheral side, and this is fed into the narrow discharge groove, preventing the chips from curling and forming straight chips. It is discharged. Therefore, unlike conventional drills, continuously curled chips (hazardous to wrap around machine parts)
is prevented from being discharged.

When the groove width ratio is 0.1, the width of the chip discharge groove 3 is 1.4 mm for a 10 mm diameter drill and 4.2 mm for a 30 mm diameter drill. It has actually been confirmed that small, curled chips on the center side easily pass through at the same time.

When drilling with the above-mentioned drill, the cutting edge on the center side of the recess 4 generates small chips, and the cutting edge on the outer peripheral side of the recess 4 generates a width corresponding to the width of the cutting edge. Band-shaped linear chips are generated, which rise in the chip discharge groove 3 and are discharged.

Conventionally, when drilling is performed, continuous chips are generated that are curled along the twisted groove of the drill. As a result, the chips become wrapped around rotating parts of drills and other machine tools, which is very dangerous.

However, according to the present invention, small curled chips are generated by the cutting edge on the center side of the recess 4, and belt-shaped chips with a width corresponding to the width of the cutting edge are generated by the cutting edge on the outer peripheral side of the recess 4. By passing the chips through the chip discharge groove 3, the tendency of the chips to curl is corrected into band-shaped straight chips, which makes the chips easy to break. Therefore, the discharge of chips is extremely difficult. It is done smoothly and smoothly.

In this way, the cutting edge at the center generates very small chips, and the cutting edge at the outer periphery generates band-shaped linear chips, so the chip evacuation groove 3 should be narrow. Chips can be discharged smoothly even under such conditions.

In addition, when the chip discharge groove 3 is formed linearly in the axial direction of the shank as shown in the figure, when the drill is rotated, the chips passing through the chip discharge groove during drilling are appropriately divided. Further, it is particularly preferable if the groove is straight because the processing cost is greatly reduced compared to the conventional method. Machining may be performed by rotating the drill or by rotating the workpiece.

Further, the chip discharge groove may be formed in a spiral shape along the shank. Furthermore, the width of the chips may be further narrowed by forming two or more recesses 4 for each cutting edge. Furthermore, if the groove cross-sectional area is set large, the recess 4 may not be formed at all.

In the above embodiment, the cutting edge 8 is continuous at the center 0, but at the center 0 it is approximately 0.5 to 1 mm.
They can be far apart from each other. Also, the shape of the cutting edge 8 does not necessarily have to be symmetrical as long as it is a curve with a large curvature near the center. Good too. Further, as shown in FIG. 5, a straight cutting edge 80 may be employed as the cutting edge. In this case, the groove width ratio is also set within the above range. 81 is a chisel.

Note that the cutting edges 8 and 81 may be formed integrally with the shank, or may be formed on a chip attached to the shank by means such as brazing. Furthermore, the material of the chip or shank is not particularly limited, and cemented carbide, high speed steel, and other alloy steels can be used. Furthermore, a feature of this invention is that the chip evacuation groove is formed in the axial direction of the shank or in a spiral shape with a groove width ratio smaller than that of conventional grooves, but it is not necessary to have a uniform cross-sectional shape along the axial direction of the shank. ,
The groove width ratio and the groove cross-sectional area may be changed as necessary.

As explained above, the present invention significantly reduces the number of chip evacuation grooves compared to the conventional drill, thereby improving the bending and torsional rigidity of the drill, and particularly improving the machinability of deep holes.

[Brief explanation of the drawing]

Fig. 1 is a side view of a drill showing an embodiment of the present invention, Fig. 2 is a bottom view thereof, Fig. 3 is a side view of Fig. 1, Fig. 4 is a sectional view taken along the - line in Fig. The figure is a bottom view showing another embodiment. 1... Shank, 2... Chip, 3... Chip discharge groove, 4... Recess, 8, 80... Cutting blade.

Claims (1)

[Claims] 1 The groove width ratio of the chip discharge groove is set within the range of 0.3 to 0.1, and the cutting edge is formed by a center cutting edge and an outer cutting edge, and a recess is formed between them. Featured drill.