JPH0146245B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an annular cutter for forming holes in a workpiece.

Common problems with annular cutters include wear and chipping of the radially inner edges of the cutting teeth. This problem is thought to be caused by metal chips frequently becoming clogged between the inner circumferential surface of the teeth and the outer circumferential surface of the central disc portion of the workpiece being cut by the blade during cutting. These chips gradually increase in size and are welded to the inner peripheral surface of the cutter near the tip edge of the cutter. Deposition of metal on the inner circumferential surface of the teeth causes significant wear and increases the torque required to rotate the blade. In addition, not only is heat generation further accelerated, but wear becomes excessive, and function stoppage due to chipping or breakage is accelerated.

An object of the present invention is to solve the problems of wear, chipping, and breakage caused by accumulation of chips around the inner peripheral surface of a cutter.

A particular object of the present invention is to form an annular cutter in such a way that the surface contact of the inner circumferential surface of the cutter with the central disc portion which the cutter is forming is minimized.

Other features and advantages of the invention will become apparent from the following description and description of the drawings.

In the drawings, a cutter according to the invention is designated as a whole by 10. The cutter 10 has a shank 12 at its upper end, and an annular side wall 14 extends downwardly from the shank 12. The lower end of this side wall 14 has a plurality of cutting teeth 16 spaced apart in the circumferential direction.
is formed on the side wall 14, and the radial depth between the teeth 16 is approximately 1/2 of the thickness of the side wall 14.
A helical groove 18 is formed at the top. Each helical groove 18 is thus radially juxtaposed to the web 20. In a preferred illustrated embodiment of the invention:
Each tooth portion 16 is formed with three cutting edges offset in the radial and circumferential directions, namely an inner cutting edge 22, an intermediate cutting edge 24, and an outer cutting edge 26. Inner cutting edge 22
An intermediate cutting edge 24 is formed at the lower end of each web 20, and an inner groove 28 and an outer groove 30 are formed near the adjacent portion of the web 20 to accommodate chips generated by the cutting edges 22, 24. It is formed. The inner cutting edge 22 is defined by the lower end of the rear surface 27 of the inner groove 28, and the intermediate cutting edge 22 is defined by the rear surface 29 of the outer groove 30.
is defined by the lower edge of On the other hand, the outer cutting edge 26
is defined at the lower end of the rear surface 31 of the spiral groove 18.

The inner cutting edge 22 and the intermediate cutting edge 24 are interconnected at a circumferential shoulder 32, and the intermediate cutting edge 24 and the outer cutting edge 26 are interconnected at a radius 34. Each of the teeth 16 is formed with a pair of counterfeed surfaces 36, 38 extending circumferentially rearward from the cutting edges 22, 24, 26, for example, in a direction inclined upwardly by about 8° to 10°. Therefore, these three cutting edges 22,
24 and 26 are shifted in the vertical direction. Further, the counterbored surface 36 slopes radially inwardly and axially upwardly, and the counterbored surface 38 slopes radially outwardly and axially upwardly. These counter-challenged surfaces 36 and 38 are in contact with each other at a ridge 40. When the chip load acting on the cutter 10 is large, the second chamfer surface 36 is tilted in the radial direction by an angle of +10° to -3° with respect to the horizontal plane.
8 is preferably inclined radially by about 20° to 25°.

When each cutting edge 22, 24, 26 is shifted in the vertical direction by a distance equal to or greater than the cutting depth per rotation of the blade 10, each cutting edge 22, 24, 26 cuts out a separate chip. Since the cutting edges 22 and 24 are inclined in the radial direction, these chips are sent upward through the inner groove 28 and the outer groove 30 and reach the helical groove 18. Similarly, chips generated by the outer cutting edge 26 are
Since they are fed upwardly from the adjacent helical grooves 18, as a result all the chips are smoothly and easily discharged upwardly through the inclined helical grooves 18.

As shown in FIG. 2, the inner circumferential surface of the side wall 14 is radially outwardly doubled to define a gap 42, thereby separating the inner cutting edge 22 of each tooth 16 from the inner circumferential surface of the side wall 14. A narrow margin a is left which extends circumferentially backwards and upwards. The gap 42 is preferably formed by removing metal from the inner circumferential surface of the side wall 14 with a cylindrical blade, and in that case, a second recess is defined by a part of the arc 44 in the circumferential direction. Ru. The maximum radial depth of the void 42 due to the cutout is between about 0.13 mm and 0.64 mm (0.005 inch and 0.025 inch), preferably between about 0.25 mm and 0.38 mm (about 0.010 inch and
0.015 inch). In order to release chips that are about to get stuck in the gap 42, the second recess is extended rearward to the inner groove 28 of the next tooth 16.
It is necessary to provide an escape path as shown at 46 in FIG. The circumferential width of margin a is approximately 0.25 mm to 1.52 mm (approximately 0.010 to 0.060 inch)
between, preferably about 0.38mm (about 0.015 inch)
shall be. When the gap 42 is formed using a cylindrical blade so as to become gradually narrower in the direction toward the inner cutting edge 22, the width of the margin a is preferably about 0.25 mm. However, when the gap 42 is machined as a groove having a substantially uniform depth in the radial direction, in order to prevent the strength of the tooth portion 16 from decreasing significantly, the width of the margin a is It should be approximately 0.25 mm (0.010 inch) or more depending on the depth of the direction.

The rear surface 27 of each inner groove 28 is approximately
It is tilted backwards and upwards at 60°. As previously mentioned, the lower end of this rear surface 27 defines the inner cutting edge 22 in cooperation with the counterfeel surface 36. The margin a has a width in the direction parallel to the rear surface 27 of the inner groove 28 so that the width is kept substantially constant when the second chamfer surface 36 is ground to sharpen the tooth portion 16. Preferably, it is formed substantially uniformly. Such a uniform width of the margin a allows the cutting tool that forms the gap 42 due to the second cut to be aligned with the cutting edge 2.
The rear surface 2 of the inner groove 28 forming the front rake surface of 2
This can be achieved by orienting the cutter 10 in a direction substantially parallel to 7 and oblique to the central axis of the cutter 10. In FIG. 3, the dashed line 48 represents the arc 44 of the air gap 42.
The outline of the inclined blade that causes this is shown in the horizontal plane. The gap 42, which is the second cut-out portion, may extend upward over the entire height of the side wall 14, but if the height of the margin a is made to substantially correspond to the vertical dimension of the tooth portion 16, The result is obtained. For example, as shown in FIG. 3, the gap 42 defined by the counterbore extends slightly above the upper end of the outer groove 30.

As already mentioned, when using the general type of annular cutter mentioned above, the inner peripheral surface of the side wall of the cutter,
There is a problem in that chips get stuck between the central disk formed by the cutter and the outer circumferential surface. This problem is substantially eliminated by providing a narrow margin a. That is, even if chips enter between the inner circumferential surface of the cutter and the center disc, a high unit pressure acts on this due to the narrow margin a, so the chips will be broken, but at least they will be sufficiently worn away. After being discharged into the cavity 42, it passes through the relief passage 46 to the next inner groove 28.
sent radially outward until In this way, the narrow margin a prevents chips from accumulating between the inner circumferential surface of the cutter and the outer circumferential surface of the disk portion, and the problems caused by this are solved.

[Brief explanation of drawings]

FIG. 1 is a side view of the annular cutter according to the present invention, and FIG.
The figure is a plan view of the main part showing the lower end, and FIG. 3 is a sectional view taken along line 3-3 in FIG. 1. 10... Annular cutter, 14... Side wall, 16... Teeth, 18... Spiral groove, 22, 24, 26... Cutting blade, 28, 30... Groove, 27... Rear surface of groove 28,
29...Rear surface of groove 30, 42...Gap, a...Margin, 46...Escape path.

Claims (1)

[Claims] 1. The main body is provided with a substantially cylindrical side wall, and a plurality of teeth are formed around the lower end of this side wall at intervals in the circumferential direction, and around the outer peripheral surface of the side wall, adjacent teeth are formed. A plurality of spiral grooves are formed extending upward from between the teeth, each of the teeth is provided with at least one cutting edge extending in the radial direction, and chips cut by the cutting edge are removed in the radial direction. grooves extending radially outwardly from the inner circumferential surface of the side wall to the helical groove such that each groove can be discharged outwardly and upwardly into the helical groove; By providing a rear surface in the radial direction extending upward from the inner portion in the direction, and by recessing the inner peripheral surface of each tooth portion outward in the radial direction, the inner peripheral surface of the tooth portion and the annular cutter can be machined. By defining a gap in the circumferential direction between the central disk portion that is being formed on the object and spacing this gap in the circumferential direction from the rear surface of each groove, the inner peripheral surface of each tooth portion is . An annular cutter, characterized in that each cutting edge has a narrow margin extending rearward and upward from the inner portion in the radial direction. 2. Each toothing is provided with at least two radially spaced cutting edges, the rear surface of the groove extending radially upwardly from the inner cutting edge. The annular cutter according to item 1. 3. A chip escape path is formed from each gap to the next groove by extending the gap circumferentially backward on each tooth to the groove of the next tooth. An annular cutter according to scope 2. 4 The maximum dimension in the radial direction of the void is approximately 0.13 mm ~
The annular cutter according to claim 3, characterized in that the diameter is 0.64 mm (0.005 to 0.025 inch). 5 Set the circumferential width of the margin to approximately 0.13mm to 1.52mm.
(approximately 0.005 to 0.060 inch). 6. The annular cutter according to claim 5, wherein the gap extends upward at least to the upper end of the groove. 7. The annular cutter according to claim 6, wherein the gap is defined by an arc-shaped portion of a cylinder. 8 Set the circumferential width of the margin to approximately 0.25 mm to 0.38 mm.
An annular cutter according to claim 7, characterized in that the diameter is about 0.010 to 0.015 inches. 9. Set the maximum dimension of the void in the radial direction to approximately 0.25 mm to approx.
The annular cutter according to claim 8, characterized in that the diameter is 0.38 mm (approximately 0.010 to 0.015 inches). 10. The groove according to claim 6, wherein the rear surface of the groove is inclined rearward and upward in the circumferential direction, while the width of the margin is substantially uniform in the vertical direction. circular knife.