PRECOGNITION DEVICE FOR ABNORMALITY OF TOOL

摘要

PURPOSE:To prevent the apprehension of drill breakage even during slight feed of a main spindle due to inertia by providing a coupling means to make a tool fitting shaft free from a sleeve body in both axial and rotational directions when resistance acting on the tool fitting shaft exceeds its set value. CONSTITUTION:When a damaged or wrongly selected drill and clogging chips increase resistance acting on a tool fitting shaft 8 above its fixed value during machining process, a ball 12 leaves a recess 14 formed on the protruding part 13 of the shaft 8, which can not follow the rotation of a member 4 to cause an exhaust hole 25 to get out of the position of a communicating hole 27 for shutting off the exhaust hole 25. The above-mentioned shutting off causes pneumatic pressure in an air feed passage to rise rapidly, and a pressure sensor detects the above-mentioned rapid pressure rise to input the signal of the pressure rise into a control amplifier and then into the control part of a machining center for stopping a main spindle 2 and simultaneously giving the alarm of an abnormal state. In addition to that, the shaft 8 is made free from the rotary member 4 in both axial and rotational directions simultaneously with the occurrence of the abnormal state, and therefore moves back to check the action of torque or thrust load on itself even during the continuous rotation or feed of the main spindle 2. Thus the breakage of a drill can be prevented.