Grinding machine with detection device for useable limit or grinding wheel

A grinding machine comprising:

• a bed;
• work support means mounted on said bed for rotatably supporting a workpiece to be ground;
• a wheel support slidably mounted on said bed for rotabably carrying a grinding wheel made of cubic boron nitride;
• a traverse carriage slidable in a direction parallel to the axis of said grinding wheel;
• traverse feed means for moving said traverse carriage;
• a truing head slidably mounted on said traverse carriage so as to be moved toward and away from the grinding surface of said grinding wheel;
• a truing wheel rotatably carried on said truing head;
• a detection member mounted on said truing head in a spaced relationship to said truing wheel in an axial direction of said truing wheel by a predetermined distance which is longer than the width of said grinding wheel and movable toward said grinding wheel;
• means for detecting the contact between said detection member and said grinding wheel;
• feed means for feeding said truing head toward said grinding wheel until said contact detecting means detects the contact between said detection member and said grinding wheel;
• said traverse feed means being operable to move said traverse carriage in one direction in response to the detection of the contact between said detection member and said grinding wheel by said contact detecting means so as to locate said grinding wheel between said detection member and said truing wheel;
• said feed means being operable to feed said truing head toward and past said grinding wheel by a first predetermined distance for truing said grinding wheel after said grinding wheel is located between said detection member and said truing wheel;
• said traverse feed means being operable to move said traverse carriage in said one direction to perform a truing operation on said grinding wheel by said truing wheel after said truing head is fed toward and past said grinding wheel by the first predetermined distance;
• said feed means being operable to feed said truing head away from said grinding wheel by the first predetermined distance after said grinding wheel is trued by said truing wheel;
• said traverse feed means being operable to move said traverse carriage in the other direction so as to align said detection member with one axial end of said grinding wheel after said truing head is fed away from said grinding wheel by the first predetermined distance;
• said feed means being operable to feed said truing head toward said grinding wheel after said detection member is aligned with the one end of said grinding wheel, said contact detecting means being actuated to detect the contact between said detection member and said grinding wheel during feed movement of said truing head toward said grinding wheel, and said detection member being ground by said grinding wheel by an amount corresponding to a wear amount for each truing operation of said truing tool after the detection of the contact between said detection member and said grinding wheel by said contact detecting means;
• truing tool wear detection means for detecting a total wear amount of said truing tool based upon the wear amount for each truing operation after each truing operation;
• and
• arithmetic and judgement means coupled to said truing tool wear detection means for judging whether or not said grinding wheel has been worn down to a predetermined size limit based upon at least said total wear amount of said truing tool.