JPS63318207A - Drill - Google Patents

Abstract

PURPOSE:To enable accurate perforation by forming a sub-groove in such a way that a secondary cutting edge is positioned on the thick-wall part side of a drill from a straight line connecting the sub-groove side end of a main cutting edge and the end of outer periphery on the sub-groove side of a chisel edge. CONSTITUTION:A sub-groove 4 is formed in such a way that a ridge line which is the edge of a secondary cutting edge 1b is positioned on the thick-wall part 6 side of a drill 10 from a straight line connecting the points on each cutting edge line of the sub-groove side end of a main cutting edge 1a and the opposite sub-groove side end of a chisel edge 3. Thereupon, the drill 10 having thus formed end parts will have a fairly shorter chisel edge 3 than the chisel edge of a drill having no sub-groove 4, improving the biting property into a workpiece while making it hard to cause a walking phenomenon. Accordingly, the rotation center of the drill 10 can be effectively prevented from moving, reducing cutting resistance while improving a cutting property to carry out accurate perforation.

Description

TECHNICAL FIELD The present invention relates to a drill, and more particularly to a drill with a minor groove.

Conventional technology In the past, hole drilling with a drill was performed based on hole accuracy, that is, hole enlargement, hole pitch accuracy, hole surface roughness, etc.
Various measures have been proposed to improve this. For example, one method is to improve the chisel part. In FIG. 4, an ordinary drill 30 generally has a long chisel blade 35, which causes problems such as poor biting of the drill.
There are problems such as walking phenomenon or increased cutting resistance. To solve these problems, thinning has generally been performed to improve machinability. However, depending on the skill of the processing, this thinning may actually increase the thrust force. Therefore, the thinning process performed by the user during re-grinding is performed with great difficulty. In order to improve this, as an alternative to thinning, we formed a sub-groove on the bottom of the drill bit 134, thereby shortening the length of the chisel blade 35 and improving the flow of chips at the chisel part, thereby improving the accuracy of hole machining. A drill is available for this purpose (Special Publication No. 5727/1983)
.

The drill 40 has a groove consisting of a main groove 44 and a sub groove 43,
The main cutting edge 4I formed by the main groove 44 and the main cutting edge 41
The minor groove 43 is provided with a corresponding secondary cutting edge 42 and a chisel blade 45 continuous with the secondary cutting edge 42 . The secondary cutting edge 42 is formed to extend linearly from the outer peripheral end of the chisel blade 45 to the main cutting edge 41.

However, in the drill 40, the accuracy of the drill hole is greatly influenced by the mutual positional relationship between the secondary cutting edge 42 and the chisel blade 45.

Therefore, the technical problem to be solved by the present invention is to define the mutual positional relationship between the secondary cutting edge and the chisel blade, and to provide a drill that can drill holes with high precision. It is to be.

Configuration of the present invention In order to achieve the above technical problem, the present invention was configured as follows.

That is, in a drill whose groove is composed of a main groove and a sub-groove, and which is composed of a main cutting edge corresponding to the main groove, a secondary cutting edge corresponding to the sub-groove, and a chisel blade, the secondary cutting The minor groove was formed so that the blade was located closer to the flesh portion of the drill than the straight line connecting the minor groove side end of the main cutting edge and the outer peripheral end of the chisel blade on the minor groove side.

Effect According to the above configuration, the minor groove for forming the secondary cutting edge is
By being formed so as to sink into the flesh side of the drill, the tip angle near the chisel becomes small. In other words, the tip of the drill is formed in the shape of a mountain with a steep slope.

If the tip angle becomes smaller, the biting of the drill into the work material will be improved.

Furthermore, when the drill bites into the workpiece, if the drill rotates around its rotation center, the walking phenomenon of the drill will not occur, but since the chisel blade has a substantially flat shape,
A point on the chisel blade on either the left or right side of the rotation center becomes the rotation center, and the drill may rotate around the rotation center opening. This is called the walking phenomenon, and to prevent this, it is necessary to make the chisel blade as short as possible.

In other words, as in the present invention, by forming the sub-grooves, it is possible to shorten the length of the rechisel blade.

That is, the minor groove with the above structure improves the bite property and effectively reduces the walking phenomenon.

EXAMPLE An example of the present invention will be specifically described below with reference to FIGS. 1 to 3.

FIG. 1 is a front view showing the tip of the drill, in which IO indicates the drill, and the drill IO has a cutting edge 1 at the tip.
and a chisel blade 3, a cutting edge section (not shown) consisting of a roughly conical cutting edge section, a groove section and a margin section 7 that serve as an escape route for chips, and a drill fixed to the drive section side. and a shank portion (not shown).

Further, the groove portion includes a main groove 5 and a sub-WII4. The minor groove 4 is located at the bottom of the main groove 5 near the end of the chisel blade 3.
Tip cutting blade! The groove is formed toward the shank portion side along the main groove direction, and has a generally U-shaped cross section toward the center of the drill. Furthermore, the tip cutting edge l is −, the main groove 5
The main cutting edge 1a is formed by the cooperation of the auxiliary groove 4 and the margin part 7, and the secondary cutting edge tb is formed by the cooperation of the minor groove 4 and the margin part 7. The secondary cutting edge 1b becomes a cutting edge that continuously connects the main cutting edge 1a to the chisel blade 3. Moreover, in the minor groove 4, the edge line of the secondary cutting edge 1b is a straight line connecting points on each cutting edge line of the minor groove side end of the main cutting edge 1a and the corresponding minor groove side end of the chisel blade 3. It is formed so as to be located closer to the flesh part 6 of the drill ring 0 than the drill ring 0.

According to the above configuration, the cutting edge of the drill IO has each cutting edge line in the center of the drill, that is, in the vicinity of the chisel blade 3.
In other words, the ridgeline of each cutting edge is formed as shown in FIG. In the figure, the chisel blade 3 (line C-0-D) is the apex of the conical tip of the drill lO (C'-D'
line), and the secondary cutting edge 1b (C-E-B
line) becomes the C'-E'-B° line. Also, main cutting edge 1
a (B-A line) is formed as a <B'-A' line following the secondary cutting edge tb.

Note that the virtual straight line portion 1c in FIG. 1 corresponds to line B'-C' in FIG. Note that the drill 10 is formed with one cutting edge, one groove, etc. on each of the left and right sides with respect to the radial center line of the drill, and the above description describes only one of them.

Drill IO with a tip formed as described above
is a chisel blade of a drill without a minor groove (X' in Figure 2)
-C'-D'-Y' line) It has a considerably shorter diesel blade 3, which improves the biting property on the workpiece and has characteristics that make walking phenomenon less likely to occur. Furthermore, the drill is provided with a sub-groove, and the sub-groove is different from the conventional sub-shoulder drill formed as shown in line B-C in FIG. When compared with the drill 10 according to the example, the latter drill 10 has a portion near the chisel blade 3 formed in a chevron shape having a steeper slope.

Therefore, the tip angle of the vicinity of the chisel blade 3 changes depending on the manner in which the minor groove is formed. Generally speaking, the smaller the tip angle, the better the biting ability of the drill, and the larger the tip angle, the easier the drill will move on the surface of the workpiece. It has the following relationship.

Therefore, when forming a minor groove, the mutual positional relationship between the secondary cutting edge 1b and the chisel blade 3 is deeply related to the accuracy of the drill hole, and the above-mentioned configuration is suitable for improving the accuracy of the hole. It is.

A specific example of the drill according to the above embodiment will be shown below. The drill used here had a drill diameter of lOn+m, and the blade part was coated to improve wear resistance. In addition, the secondary cutting edge is as explained in the above embodiment,
The minor groove is formed so that it is located on the flesh side of the drill from the straight line connecting the point on the cutting edge line of the chisel blade and the minor groove side edge and the point on the cutting edge line of the main cutting edge and the minor groove side edge. There is. in particular,
The point of contact between the secondary cutting edge and the main cutting edge is radius IN from the drill center O.
+=2.2mm above, and the secondary cutting edge is located at a maximum of I2. A roughly curved cutting edge line having a point on the cutting edge that penetrates by =0.3n+m is provided. A drill with the above configuration, hereinafter referred to as the first drill, has the same drill diameter and the same blade coating, and the secondary cutting edge is formed in a straight line from the main cutting edge to the chisel blade. The enlargement amount of the hole was measured for each number of holes drilled under the following conditions using the drill, hereinafter referred to as the second drill. The results are shown in Figure 3.

Here, the conditions for drilling are as follows: Cutting speed: 25m/min.

Feedback; Q, l 5mm/rev
.

Workpiece material: 550C (hardness HB240-250) Cutting length: 20mm penetration Cutting oil: Uses water-soluble cutting oil Machine tool: Machining center.

In the figure, the measurement results from the first drill (←---) are the same as those from the second drill.
Compared to that with a drill (...), all hole drilling shows superiority in terms of hole accuracy in terms of number, and each hole drilling has a large variation in hole diameter enlargement for each number. The result is less than that of the 2nd drill.

That is, in a drill provided with a sub-groove, it can be said that the form of the sub-groove is deeply related to the accuracy of the drill hole. That is, even drills with the same chisel blade length have different drill loading degrees. In other words, the quality of the biting ability of the drill is closely related to the form of the minor groove. As is clear from the experimental results, the first drill can be judged to be superior to the second drill in terms of the mutual positional relationship between the secondary cutting edge and the chisel blade, and therefore, in order to improve hole accuracy, is preferably defined the same as that of the first drill.

Effects of the Invention According to the above configuration, the vicinity of the chisel blade is formed in the shape of a mountain with a steep slope. Therefore, the tip angle of the drill tip becomes smaller and the chisel blade becomes shorter, so when cutting,
The biting property against the material to be cut is improved, so that so-called walking phenomenon is less likely to occur.Therefore, it is possible to effectively prevent the center of rotation of the drill from moving, and the cutting resistance is reduced, resulting in improved cutting performance. In this way, the above-mentioned effects of the conventionally employed minor grooves are not impaired in any way, and by defining the positional relationship of the secondary cutting edge corresponding to the minor groove with respect to the chisel blade as in the present invention,
Furthermore, it is possible to ensure hole accuracy higher than that of conventional sub-grooved drills.

In addition, the difficulty of thinning after each re-grinding, which conventionally had a great effect on the accuracy of the hole, is eliminated because the drill according to the present invention can drill holes with high accuracy without thinning. be done.

In other words, drilling can be performed simply by sharpening the cutting edge at the tip of the drill.

[Brief explanation of drawings]

FIG. 1 is a front view of the principal part of the tip of a drill according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the cutting edge line of the cutting edge of the drill, and FIG. 3 is a hole drilled using the drill. The light is a bar graph showing the enlargement margin of the hole diameter during machining, and FIG. 4 is a front view of the main part of the tip of a conventional drill. l...Tip cutting edge, 1a...Main cutting edge, 1b...Secondary cutting edge, lc...Virtual straight line, 3...Chisel blade, 4...
・Minor groove, 5...Main groove, 6...Meat part, 7...Margin part,! 0...Drill.

Claims (1)

[Claims] 1. The groove is composed of a main groove (5) and a sub-groove (4), and the tip cutting edge is a main cutting edge (1a) formed by the main groove (5), and a main cutting edge (1a) formed by the main groove (5). A drill (10 ), the secondary cutting edge (1b) is closer to the edge of the drill (10) than the straight line connecting the minor groove side end of the main cutting edge (1a) and the outer peripheral edge of the minor groove side end of the chisel blade (3). So that it is located on the meat part (6) side,
A drill characterized in that the above-mentioned minor groove (4) is formed.