Rotary grinding tool and its production method

1. A rotary grinding tool with reduced noise level, comprising

a metal disk having a grinding surface on at least a part of a surface of the metal disk, the grinding surface having hard grains having a Mohs hardness in excess of 9 brazed thereon at a surface density of at least 20 grains/cm 2 , and

a holder for supporting the metal disk, the holder having securing means for securing the holder on a rotary shaft of a rotary drive unit, the metal disk being joined to the holder,

wherein the surface of the metal disk has a front surface, a sloped surface, a side surface, and a rear surface, the front surface, the sloped surface, and the side surface being continuously formed in this order from a center side to a peripheral side of the metal disk, the rear surface, being located at the back of the front surface and the sloped surface and adjacent to the side surface, the front surface being perpendicular to a rotary axis, and the side surface being parallel to the rotary axis.

2. A rotary grinding tool with reduced noise level according to claim 1 , wherein the metal disk and the holder are joined to each other by bolts.

3. A rotary grinding tool with reduced noise level according to claim 1 , wherein a space is formed on a front side of the securing means by joining the metal disk with the holder, the space having a volume of at least 7000 mm 3 .

4. A rotary grinding tool with reduced noise level according to claim 1 , wherein

the metal disk has a thickness of 3.0 to 6.0 mm and a weight of 100 to 1000 g,

the holder has a thickness of 3 to 10 mm, and

a percentage of contact area of the metal disk and the holder in an area of the rear surface of the metal disk is 30 to 100%.

5. A rotary grinding tool with reduced noise level according to claim 1 , wherein the metal disk comprises a stainless steel material, and the holder comprises an aluminum alloy material.

6. A rotary grinding tool with reduced noise level according to claim 1 , wherein the sloped surface of the metal disk has a stepped configuration.

7. A rotary grinding tool with reduced noise level according to claim 1 , wherein the front surface has a first width (W 1 ) in radial direction in a projected plane seen from the front side, and the sloped surface of the metal disk has a second width (W 2 ) in the radial direction in the projected plane seen from the front side, and W 1 /W 2 is greater than 2.0, and W 2 is at least 1 mm.

8. A rotary grinding tool with reduced noise level according to claim 1 , wherein the sloped surface of the metal disk has an area of at least 400 mm 2 .

9. A rotary grinding tool with reduced noise level according to claim 1 , further comprising a vibration absorber comprising an organic, inorganic, or metal material provided at least at a part of a boundary or joint between the metal disk and the holder.

10. A method for producing a rotary grinding tool with reduced noise level according to claim 1 , the method comprising:

coating a filler powder mixed with an organic binder on at least a part of the front surface, the sloped surface, the side surface, and the rear surface of the metal disk to a thickness corresponding to 20 to 60% of the average particle diameter of the hard grains having a Mohs hardness in excess of 9,

applying the hard grains having a Mohs hardness in excess of 9 to a surface density of at least 20 grains/cm 2 ,

maintaining the metal disk at a reduced pressure of up to 10-4 Torr at a temperature of 1000 to 1040° C. for 10 to 50 minutes to prepare the metal disk having a grinding surface, and

joining the metal disk with the holder to obtain the grinding tool.