JPS63120008A - Drill - Google Patents

Abstract

PURPOSE:To aim at the relief of burnishing torque, by disposing a cutting edge so as to cause the line segment that connected its outer circumferential side ends themselves to be dislocated in the radial direction against a drill axis. CONSTITUTION:After countersinking is over, a cutting edge 3a facing toward an arrow X at the side of a turning center O1 bites into a hole 6 as a whole, and this hole is gradually widened in diameter, simultaneously with this, an edge of the hole 6 is cut by a ridgeline part 4a of a margin part 4, thus a cylindrical hole 7 is formed up. In this connection, since the ridgeline part 4a is pressed to the X direction, the margin part 4 will not collide with a wall part 7a so that torqure is not increased at all. Next, in proportion as a body 1 moves to the side of the center O1, the hole 7 is further widened in diameter by the cutting edge 3a and the ridgeline part 4a, whereby the torque is in creased. Then, when an axis O accords with the center O1, a diameter of the hole 7 accords with that of each margin part 4.4 as well, and since no vibration occurs in the body 1 to be guided these margin parts 4 and 4, burnishing torque is sharply relievable.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a drill that can reduce cutting torque and therefore facilitate high-speed cutting and drilling of difficult-to-cut materials. It is.

[Prior Art] A twist drill is generally known as a tool for drilling holes. This twist drill has two twisted grooves formed on the outer periphery of the drill body, and
A margin portion is formed on the outer periphery of the drill body that is continuous with the wall portion facing the rotational direction of these helical grooves, and two cutting edges extending toward the outer periphery are formed on the tip flank of the drill body. Here, the cutting blades are arranged point-symmetrically across the axis when viewed in the axial direction, and the diameter across the outer peripheral ends of the cutting blades is the diameter of the twist drill. When performing cutting using such a twist drill, the cutting edge starts biting and forms a forest-like hole, so-called countersunk cutting. A cylindrical hole extending in the direction is formed, and at the same time, the margin part enters the cylindrical hole and bites into the hole.

The drill body is guided by the margin portion, and stable cutting is performed.

[Problems to be Solved by the Invention] However, in such a twist drill, when the countersinking process is completed and the margin part enters the cylindrical hole,
Large frictional resistance occurs between the margin and the inner wall of the hole, resulting in excessive cutting torque (hereinafter referred to as burnishing torque), leading to frequent accidents such as breakage of the drill body. . In other words, in countersunk machining, the drill body is not guided, so
The tip of the drill body vibrates in an arc.

However, the rotation locus of the margin section at this time is an arc with a diameter larger than the diameter of the cylindrical hole, so when the margin section enters the cylindrical hole, it is as if it were entering a hole with a smaller diameter than the drill diameter. , the margin portion collides with the inner wall of the hole, resulting in large frictional resistance.

[Object of the invention] This invention was made in view of the above circumstances, and can reduce the burnishing torque when the margin part enters the cylindrical hole, thereby preventing accidents such as breakage of the drill body. The object of the present invention is to provide a drill that can not only perform high-speed cutting but also facilitate machining of difficult-to-cut materials.

[Means for Solving the Problems] The drill of the present invention is provided with two chip discharge grooves that open at the tip flank of the drill body on the outer periphery of the drill body, which is rotated about an axis, In the drill, a margin part is provided on the outer periphery continuous to the wall part facing the rotational direction of the discharge groove, and two cutting blades extending from the inner periphery side to the outer periphery side are provided in the tip relief. are arranged so that a line segment connecting their outer circumferential ends is offset in the radial direction with respect to the axis.

[Function] In the drill with the above configuration, the cutting blades are arranged so that the line connecting the outer circumferential ends of the cutting blades is offset in the radial direction with respect to the axis of the drill body, so that countersunk cutting is possible. At this time, the drill body rotates around the midpoint of the line segment connecting the outer peripheral ends of the cutting blades.

Then, when the diameter of the forest-like hole formed by countersunk cutting becomes the same as the diameter across the outer circumference of the cutting blade, countersunk cutting ends, and cutting into the hole begins. However,
In this state, the axis of the drill is deviated from the rotation center, so a restoring force always acts on the drill body toward the rotation center, and the drill body gradually moves toward the rotation center. Then, the diameter of the hole is gradually expanded by the cutting blade facing the moving side, and the edge of the hole is continuously cut by the ridgeline of the margin part continuous with the cutting blade to form a cylindrical hole, and the other side The cutting edge is rarely used for cutting. At this time, since the ridgeline portion of the margin portion is pressed in the moving direction of the drill body, the margin portion does not collide with the wall portion of the cylindrical hole.

Therefore, the cutting torque during biting cutting into the hole is only the cutting resistance caused by one cutting edge and the ridgeline portion of the margin portion, and the burnishing torque is significantly reduced.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 5. FIG. 1 is a plan view showing a twist drill according to an embodiment. In this figure, reference numeral 1 indicates the drill body. The drill body l is rotatable around an axis O, and has two twisted grooves (chip discharge grooves) 2 on its outer periphery that open at its tip flank 1a.
・2 is provided. These twisted grooves 2 are arranged so as to be offset from each other in the circumferential direction so as to be asymmetric with respect to the axis 0 when viewed in the axial direction.

Cutting edges 3a and 3b are formed at the intersection of the wall portions of the helical grooves 2 and 2 facing the rotational direction and the tip flank surfaces 1a. The positions of these cutting edges 3a and 3b are the helical grooves 2 and 2.
They are offset from each other in the circumferential direction corresponding to the positions of. Therefore, the line segment e connecting the outer circumferential ends of the cutting blades 3a and 3b is radially offset from the axis O of the drill body l. Note that the deviation angle O of the cutting edges 3ilL and 3b is set to 2 to 15 degrees.

Furthermore, margin portions 4 are formed on the outer peripheral portions of the torsion plates 2, 2, which are continuous with the wall portions facing the rotational direction.

One of these margin parts 4 is provided wider than the other, and a part of the margin part and the other margin part 3 are located on the diameter line Q1 of the drill body l. Therefore, the maximum diameter across the margins is equal to the drill diameter.

Next, the operation when drilling a hole with such a twist drill will be explained with reference to FIGS. 3 to 5. Here, FIG. 5 is a diagram showing the cutting torque during machining. In the figure, the solid line shows the cutting torque in the above twist drill, and the broken line shows the cutting torque in the conventional twist drill. In addition, A is the range of countersunk cutting,
B shows the range of cutting that bites into the hole, and C shows the range of stable cutting when the drill body l is guided by the margin parts 4.

First, in countersunk cutting, the cutting blades 3a and 3b bite into the workpiece 5, and the drill body l is at the midpoint of the line segment ρ. It rotates around , and a forest-like six-six is formed. And hole 6
The countersunk cutting ends when the diameter of Q becomes equal to the length of Q. In the machining so far, the cutting edges 3a and 3b are used for cutting, and the cutting torque at that time is indicated by the arrow A in FIG.
increases linearly as shown in the range. This is because the cutting resistance acting on the cutting edges 3a, 3b increases as the machining progresses, and the value of the cutting torque is almost the same as that of a conventional twist drill.

However, in this state, the axis O of the drill body I is radially offset from the rotation center OI, so a restoring force always acts on the drill body I toward the rotation center 01 (in the direction of the arrow X in the figure). ing.

Therefore, when cutting a hole by biting, the entire cutting edge 3a facing in the direction of the arrow
The edge of the other cutting edge 3 is cut to form a cylindrical hole 7, and the other cutting edge 3
b is hardly used for cutting. At this time, since the ridgeline portion 4a of the margin portion 4 is pressed in the direction of the arrow X, the margin portion 4 does not collide with the wall portion 7a of the cylindrical hole 7. Therefore, the cutting torque at this time is
Since there is only cutting resistance due to the ridgeline portion 4a of the margin portion 4, the value of the cutting torque at the end of countersunk cutting is maintained for a while (see FIG. 5). Then, the drill body 1 gradually moves toward the rotation center 01, and the diameter of the hole 7 is further expanded by the cutting edge 3a and the ridgeline portion 4a of the margin portion 4, and the cylindrical hole 7
As the depth increases, the frictional resistance between the margin portion 4 and the wall portion 7a of the cylindrical hole 7 increases, and the cutting torque increases accordingly.

Next, when the axis O of the drill body 1 coincides with the rotation center O1, the diameter of the cylindrical hole 7 becomes the same as the diameter of the margin portions 4, and cutting into the hole is completed. At this time, since the drill body l is guided by the margin parts 4, 4, no vibration occurs in the drill body l, and the margin parts 4, 4 do not collide with the wall part 7a of the cylindrical hole 7. . Furthermore, since the cutting blades 3a and 3b are arranged circumferentially offset from each other, the combined force of the cutting resistance is always directed in a constant direction. Therefore, the vibration of the drill body l is suppressed, the margin parts 1 and 4 are not strongly rubbed against the inner wall of the hole 7, and the cutting torque in stable cutting (range C in Fig. 5) is lower than that of the conventional one. It is significantly reduced compared to the twist drill.

In the above-mentioned twist drill, it is possible to significantly reduce the burnishing torque when cutting into a hole, but also the cutting torque during stable cutting, so the drill body °l Of course, it is possible to prevent accidents such as loss of
High-speed cutting and drilling of difficult-to-cut materials can be easily performed. Further, since a force acting in a certain direction is applied to the drill body 1, vibration of the drill body 1 can be suppressed, and the occurrence of polygonal holes and so-called rifle marks can be prevented.

Further, FIGS. 6 to 9 are diagrams showing other embodiments of the present invention. The twist drill shown in these figures has two cutting edges 9a and 9b located on the tip flank 8a of the drill body 8 so as to be parallel to each other when viewed in the axial direction, and parallel to the direction in which the cutting edges 9a and 9b extend. They are arranged offset from each other in orthogonal directions, and as shown in FIG. 8, the lengths Lt, Lt of the chisels lOa and IOb are made to have a large difference. In this twist drill as well, the cutting edge 9
A line segment e connecting the outer circumferential ends of a and 9b is radially offset from the axis 0, and the same effect as in the above embodiment can be obtained. Furthermore, since there is a large difference between the lengths Lt and Lx of the chisels 10a and 10b, as shown in FIG. The cutting forces acting on the blades 9a and 9b are significantly different. Therefore, a large force acting in a certain direction acts on the drill body 8, making it possible to further reliably prevent the occurrence of vibrations.

Moreover, FIG. 1O and FIG. 11 are diagrams showing still other embodiments of the present invention. The twist drill shown in these figures has two throw-away tips (cutting edges) 12 disposed at the tip of the drill body 11 so as to be offset from each other in the circumferential direction, and each throw on the outer circumference of the drill body 11. A guide pad 13 is fixed at a position where the combined force of cutting resistance acting on the away depths 12 is directed. In this twist drill as well, the line segment g connecting the outer circumferential ends of the indexable tips 12 is deviated in the radial direction with respect to the axis 0, and the same effect as described above can be obtained. Note that the present invention is not limited to the twist drill as described above, but may be applied to a two-blade drill in which a chip discharge groove is provided along the axis of the drill body.

[Effects of the Invention] As explained above, in the drill of the present invention, two cutting edge ejection grooves are provided on the outer circumference of the drill body that rotates around the axis, and the two cutting edge discharge grooves open to the flank at the tip of the drill body. In the drill, a margin portion is provided on the outer periphery continuous to the wall portion facing the rotational direction of the cutting blade ejection groove, and two cutting blades are provided on the tip flank surface extending from the inner periphery side to the outer periphery side. The cutting blades are arranged so that the line segment connecting their outer circumferential ends is offset in the radial direction with respect to the axis, which greatly reduces the burnishing torque when the margin part enters the cylindrical hole. can be reduced to,
Therefore, not only can accidents such as breakage of the drill body be prevented, but also high-speed cutting and cutting of difficult-to-cut materials can be easily performed.

[Brief explanation of the drawing]

1 to 5 are views showing one embodiment of the present invention, in which FIG. 1 is a bottom view showing a twist drill, FIG. ■ Directional arrow view in Figure 1,
Figure 4 is a cross-sectional view to explain the state in which cutting is being performed with a twist drill, Figure 5 is a diagram showing the relationship between the depth of the machined hole and the cutting torque, and Figures 6 to 9 are the main figures. FIG. 6 is a bottom view showing a twist drill, FIG. 7 is a view taken in the direction of the ■ arrow in FIG. 6, and FIG.
FIG. 8 is an enlarged view of the part indicated by the arrow ■ in FIG. 10 is a bottom view showing the twist drill, and FIG. 11 is a view taken in the direction of the cutting direction in FIG. 10.・・・・・・
Tip flank surface, 2... Twisted groove, 3a...
- Cutting blade, 3b... Cutting edge, 4... Margin, 8... Drill body, 8a... Tip flank, 9a... ...Cutting blade, 9b...Cutting blade, II...Drill body, 12...Throwaway depth (cutting blade), 0.
...Axis line, e... Line segment.

Claims (1)

[Claims] Two chip evacuation grooves that open at the tip flank of the drill body are provided on the outer periphery of the drill body, which is rotated about an axis, and an outer periphery that is continuous with the wall portion of these chip ejection grooves facing in the direction of rotation. In the drill, the tip flank is provided with two cutting edges extending from the inner circumferential side to the outer circumferential side, and the cutting edges are connected to each other at their outer circumferential ends. A drill characterized in that the dotted line segments are arranged so as to be offset in the radial direction with respect to the axis.