JPH0329526B2 - - 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. Similarly, the chips accumulated on the inner circumferential surface of the cutter create a radial load on the cutter, resulting in the formation of additional holes, resulting in a poor finish and a tendency to break. Therefore, it can be seen that by minimizing friction and effectively cooling the cutting edge, the life of the cutting tool will be extended. An object of the present invention is to solve the problems of wear, chipping, heating, and damage 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 so that the surface contact of the inner circumferential surface of the cutter with the central disc portion that the cutter is forming is minimized. Another object of the invention is to provide a large volume coolant passage directly adjacent the blade teeth. 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 the preferred illustrated embodiment of the invention, each tooth 16 has three radially and circumferentially offset cutting edges: an inner cutting edge 22, an intermediate cutting edge 24, and an outer cutting edge 26. It is formed.
The inner cutting edge 22 and the intermediate cutting edge 24 are formed at the lower end of each web 20, and near the adjacent portion of the web 20 there is an inner groove 28 for storing chips generated by the two cutting edges 22, 24; An outer groove 30 is formed. The inner cutting edge 22 is a rear surface 2 of the inner groove 28.
7, the intermediate cutting edge 24 is defined by the lower end of the outer groove 3
0 at the lower end of the rear surface 29. 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 rear surface is flat as a whole and has grooves 2
The upper ends of 8 and 30 are somewhat rounded. 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 circumferential shoulder 34. As shown in FIG. 2, each shoulder 32, 34 has a
It forms a radius that connects with the next continuous cutting edge. Each tooth portion 16 has cutting edges 22, 24, 26.
a pair of counterfeit surfaces 36, 3 extending circumferentially rearwardly, e.g., upwardly at an angle of about 8° to 10°;
8, these three cutting edges 22, 24, 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. Depending on the purpose of use of the cutter, the second bevel surface 36 is radially inclined at an angle of +25° to -3°, preferably approximately 15° relative to the horizontal plane, and the second bevel surface 38 is inclined at an angle of approximately 5° to 35° in the radial direction. , preferably 5°~
It is possible to tilt it by 10°. Each cutting edge 22, 24, 26 is offset vertically and/or circumferentially by a distance such that each cutting edge cuts a separate chip or at least cuts a thin unitary material that tends to connect the chips. ing. Since the cutting edges 22 and 24 are inclined in the radial and axial directions, these chips are deposited in the inner groove 28 and the outer groove 3.
0 and is sent upwards to reach the spiral groove 18. Similarly, the chips produced by the outer cutting edge 26 are directed upwardly from the adjacent helical groove 18, so that all the chips are smoothly and easily discharged upwardly through the inclined helical groove 18. . As shown in FIG. 2 and FIG.
It is cut radially outward from a vertically extending line VL just behind the intersection line 41, and an extremely narrow margin m extending upward is formed between the intersection line 41 and the vertical extension line VL. In the embodiment of FIG. 2, the space 42 is formed by removing metal from the inner peripheral surface L of the tool wall at each tooth by a cylindrical cutter or grinding wheel 43; A portion of the circular arc 44 in the direction defines a counterfeit surface 46 . It is desirable that the inner circumferential surface of the cutter be counter-bored in a suitable manner as shown in FIG. is ground into a flat surface 46 by a grinding wheel 48 oriented radially through each groove 28 . Further, in this case, the width of the sky 50 gradually increases toward the rear. The maximum width of margin m is approximately 1.02 mm (0.040 inch)
should not exceed approximately 0.05~0.38mm (0.002~
0.015 inch) is desirable. Narrow margins are desirable because they provide radial stability for the blade and prevent over-cutting of the hole. However, it is not essential to provide a margin for each tooth. If the inner circumferential surface of the cutter is cut directly on the line of intersection between the inner circumferential surface of the cutter and the rear surface 27 of the groove 28 (indicated by the dashed line in FIG. A lateral cutting edge is formed that extends to . This minimizes the friction between the inner peripheral surface of the cutter and the central disc formed by the cutter.
However, when manufacturing cutters according to production standards, the vertical cutting edges are formed in such a way that all vertical cutting edges are exactly spaced by the same radial distance from the axis of the cutter as a circular grinding margin m. It is difficult to double cut all the cutting edges on each knife. Therefore, it is practical and indeed desirable to countercut the cutter so as to leave a narrow inner margin on all or at least most of the teeth. The counterbored portion is formed so that the margin tapers very slightly at the axial tip of the tooth portion and gradually widens upward. This ensures that very narrow margins are created when the first cutter is manufactured and after repeated grinding of the cutter by scoring the second face and groove surface 27. Thus, as shown in FIG.
(0.002~0.005 inch), the width of the top edge is approximately 0.38mm
(0.015 inch). It is desirable that the vertical height of the margin m be slightly higher than the height of the groove 28 so that the gaps 42, 50 slightly exceed the height of the groove 28. As pointed out in the preamble, when using the general type of annular cutter mentioned above, there is a problem in that chips get stuck between the inner circumferential surface of the side wall of the cutter and the outer circumferential surface of the central disk formed by the cutter. . This problem is caused by the extremely narrow margin m combined with the air gap inside each tooth.
This can be substantially eliminated by providing . That is,
Even if chips do get stuck between the inner circumferential surface of the cutter and the central disk, the narrow margin m or the high unit pressure generated by the vertical side cutting edges will cause the chips to break or at least be completely destroyed. After being worn away and expelled into the void or passageway, it is fed radially outward to the next continuous groove and spiral groove. From the foregoing, the radial dimensions of the relief passages 42, 50 must be sufficient to accommodate any chips that enter the void. i.e. approx.
The structure is such that the cutter operates at a feed rate that results in a chip load (chip thickness) of up to 0.13 mm (0.005 inch). The relief passage thus has a radial dimension such that it connects with at least the next groove of said dimension. However, it is necessary to minimize the radial dimension of the escape channel fairly close to the trailing edge of the margin, as described above, so that the escape channel freely escapes immediately after encountering the margin. Experiment has shown that the trailing edge of the margin, or in the absence of a margin, is inclined radially outwardly at an angle of at least about 3°, preferably at least 7°, relative to the tangent at the vertical side cutting edge. If the relief channel is defined by a surface, the radial width of the relief channel should be 0.13 mm (0.005 inch) so that chips can pass close enough to the margin or side cutting edge. can be easily discharged. The angle with respect to the tangent line is shown in Figures 2 and 4.
In the figure, the angle is indicated by a and is about 12 degrees, which is suitable for a cutter having the shape shown in FIG. If the gap is formed as an arcuate channel having a maximum width between its ends, the width b of the outlet end of the channel should be at least about 0.13 mm.
(0.005 inch). If the cutter is supplied with downwardly directed coolant via the central passage 54 of the cutter shank, the air gap will of course have an additional function. That is, since the tooth portion is directly cooled with a large amount of coolant, the mass of the tooth portion is smaller than when no gap is provided. From the perspective of effectively cooling the teeth, it is desirable that the volume of the gap be as large as possible, but care should be taken not to reduce the mass of each tooth to the extent that it weakens the inherent strength of each tooth. I have to take second place. In order to clarify the results obtained with the cutter formed according to the present invention, two tests were carried out under the same conditions.
Experimental results regarding different types of cutlery are shown below. Both blades have an outer diameter of 25.4~22.2mm (1~7/8 inch)
It has the overall shape shown in FIG. The construction and dimensions of both knives are the same, with the knife designated below as "A" having no inner margin, while "B"
For the cutlery shown as , an inner margin is formed in the same manner as shown in Figure 4, and the width of the margin is approximately
0.05~0.13mm (0.002~0.005 inch). Both tools were rotated at 150 R.PM to form a hole through a 2″1018 steel bar.

【table】

[Table] From the above results, the advantages of the present invention can be easily understood. In all cases, the increase in the hole formed with cutter B was actually small and the finish was smooth. The faster the feeding speed of cutter B was increased, the smaller the horsepower and thrust required. 0.13mm for knife A
(0.005 inch) cutting load is considered to cause damage.
No experiments were conducted to apply inch loads.

[Brief explanation of the drawing]

FIG. 1 is a side view of the annular cutter according to the present invention, and FIG.
3 is a sectional view taken along line 3-3 in FIG. 1, and FIG. 4 is a plan view similar to FIG. 2 showing another embodiment of the annular cutter according to the present invention. ,
FIG. 5 is a view of FIG. 3C. 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, 50...Gap, m
...Margin, 43, 48...Grinding wheel, 46...
...Escape path, 54... Coolant passage.

Claims (1)

[Claims] 1. The main body 10 is provided with a substantially cylindrical side wall 14, and a plurality of teeth 16 are formed around the lower end of the side wall at intervals in the circumferential direction, while around the outer peripheral surface of the side wall, a plurality of teeth 16 are formed. , a plurality of spiral grooves 18 extending upward from between the adjacent tooth portions are formed, and each of the tooth portions 16 includes:
at least one radially extending cutting edge 22,2
4, 26, and radially outward from the inner peripheral surface of the side wall 14 so that chips cut by the cutting blade can be discharged radially outward and upward into the spiral groove 18. are provided with grooves 28, 30 extending into helical grooves, each of these grooves being provided with a radially rear surface 27, 29, 31 extending upwardly from the radially inner portion of each cutting edge 22, 24, 26; By recessing the inner circumferential surface of each tooth portion 16 outward in the radial direction, a radial gap 42, 50 extending in the circumferential direction is created between the inner circumferential surface of each tooth portion 16 and the center disk portion that is being formed in the workpiece. defining the inner peripheral surface L and the rear surface 2 of the innermost groove 28;
An annular cutter characterized in that the holes 42 and 50 extend rearward from a line VL extending in a substantially vertical direction and spaced rearward by about 1.02 mm (0.040 inch) from a line 41 where VL intersects with VL. 2. The cavities 42, 50 form a relief path extending radially rearward from the inner circumferential surface L of each tooth 16 to the next adjacent spiral groove 18. circular knife. 3. The sky 42, 50 is defined by a substantially vertical surface 46, and the vertical surface 46 is defined by a vertical extension line VL.
has an angle a of at least about 3° to 7° with a tangent drawn to the inner circumferential surface L, and the distance from the vertical extension VL to the radial space 42, 50 is at least about 0.13°.
mm (0.005 inch), after which the said spacing is approximately 0.13 mm.
(0.005 inch) or more. 4. On at least some of the teeth 16, the vertical extension line VL is spaced rearwardly from the intersection line 41 to define a margin m at least about 0.002 inches wide. An annular cutter according to claim 3, characterized in that: 5. In at least some of the teeth 16, the vertical extension line VL is spaced rearwardly from the intersection line 41 by at least about 0.05 to 0.38 mm.
The annular cutter according to claim 3, characterized in that a margin m is formed having a circumferential width of (0.002 to 0.015 inches). 6. An annular cutter according to claim 3, characterized in that the perpendicular surface 46 is substantially flat so that the radial dimension of the relief passage gradually increases in the radial direction. 7. An annular cutter according to claim 4, wherein the vertical extension line VL is slightly inclined rearward with respect to the intersection line 41 so that the upper end of the margin m is wider than the lower end. . 8 The margin m is at least the intersection line 41
The annular cutter according to claim 4, wherein the annular cutter is at the same height as the cutter. 9 Each tooth portion 16 is provided with a plurality of cutting edges 22, 24, 26 offset in the circumferential direction, and the innermost cutting edge 22 in the radial direction is separated from the next radially adjacent cutting edge 24. The annular cutter according to claim 3, wherein the annular cutter is located at the front in the rotation direction. 10 The vertical surface 46 is flat and the angle a with the tangent line is
10. An annular cutter according to claim 9, wherein the annular cutter is inclined radially outwardly at about 12 degrees. 11. An annular cutter according to claim 3, characterized in that the main body 10 has an axially extending passage 54 for passing a coolant.