| 摘要 |
935,030. Diamond tools. SUPER-CUT Inc. Jan. 21, 1960 [Jan. 26, 1959], No. 2278/60. Class 124. A composite rotary tubular abrasive diamond core drill 10 extending vertically and rotated about its axis in use comprises a cylindrical tubular shank 12 of uniform thickness with a passage 36 to introduce a coolant under pressure to the interior of flow downwardly, and an abrasive annulus 14, namely a diamond-impregnated matrix, fixedly-secured to the lower end of the shank 12, axially aligned and in fluid communication therewith, and with substantially cylindrical inner and outer surfaces and a flat bottom 16, the drill 10 in operation descending endwise and axially into a workpiece 22 to create therein a central cylindrical core 48 with an annular socket 46, the bottom wall 54 of which is abrasively engaged by the bottom 16 of the rotating annulus 14, the radial thickness of which is slightly greater than the wall thickness of the shank 12, so that it radially overhangs the inner and outer surfaces of the latter, whereby, on descent of the drill 10, thin inner and outer annular clearance spaces a, a<SP>1</SP> will be progressively formed in the workpiece 22 in the immediate vicinity of the shank 12 for coolant to flow downwardly on the inner surface of the shank and then upwardly on the outer surface thereof after passing radially outwardly between the bottom 16 (of the annulus 14) and the bottom 54 (of the socket 46), the said surfaces having circumferentially-spaced, vertically-extending grooves 60, 62, each spanning the vertical height of the annulus 14 and having a maximum depth no less than one-half the radial thickness of the annulus 14, the grooves 60 being radially staggered with respect to the grooves 62. Preferably, each groove is arcuate in transverse cross-section and has a maximum depth approximately 55% of the radial thickness of the annulus 14, whereas the lower end of the shank 12 has upward continuations of the grooves in the annulus 14, the total length of each groove being at least equal to the depth of cut to be made in the workpiece 22. |
