| 摘要 |
In a machine tool of the type, in which a working tool attached to a rotating main spindle rotates to subject a work to a machining work such as a grinding or cutting operation, there is provided a working tool protecting device for preventing and protecting the damage or fold of the working tool due to an excessive torque load. The working tool is exemplified by a honing machine comprising a magnetic type coupling device (25) interposed between a rotating main spindle (2), to which a honing tool or the working tool is attached, and the servo motor of a main spindle rotating drive unit for rotating the rotating main spindle (2), thereby to transmit the rotating force of the servo motor to the rotating main spindle (2) by the magnetic action. The magnetic transmission torque for transmitting the rotating force of the magnetic type coupling device (25) is set lower than a predetermined torque load (e.g., the folding torque of the honing tool) to be applied to the honing tool. As a result, it is possible to prevent and protect the damage or fold of the honing tool due to the excessive torque load.
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