| 摘要 |
PROBLEM TO BE SOLVED: To improve the abrasion resistance and lubricating performance of a bearing member and to provide a bit device of a long life. SOLUTION: The bit device has a constitution wherein a cutter member having a cutting edge is journalized rotatably in relation to a shaft and a bearing mechanism is interposed between the cutter member and the shaft. The bearing mechanism is equipped at least with a radial bearing that bears a load in the radial direction and a thrust bearing that bears a load in the axial direction, In the bit device, the surface of each bearing component is covered with a hard film of a single or a plurality of layers of a rock salt type structural crystal containing Ti as an indispensable element and constituted of a carbide, a nitride or a carbide-nitride of one or two or more kinds of substances selected from Zr, Hf, V, Nb, Ta, Cr, Mo, W, Si, B, Y or Al.
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