Abstract: A main spindle device for a machine tool that checks the seating of a tool holder using compressed air, wherein the main spindle device for a machine tool comprises: a main spindle that has a distal end face in close contact with a flange end of the tool holder; an annular recess that is formed on the distal end face of the main spindle so as to be covered by the flange end of the tool holder; an air supply flow channel that is linked to the annular recess and that supplies compressed air to the annular recess; a compressed air source that supplies air to the air supply flow channel; and a pressure detector that detects the pressure of the compressed air in the air supply flow channel. The annular recess has a first section and a second section that is deeper than the first section, and the air supply flow channel is opened to the second section.

Abstract: A main spindle device (10) for a machine tool that checks the seating of a tool holder (30) using compressed air, wherein the main spindle device (10) for a machine tool comprises: a main spindle (12) that has a distal end face (18) in close contact with a flange end of the tool holder (30); an annular recess (25) that is formed on the distal end face (18) of the main spindle so as to be covered by the flange end of the tool holder; an air supply flow channel (21) that is linked to the annular recess and that supplies compressed air to the annular recess; a compressed air source (23) that supplies air to the air supply flow channel; and a pressure detector (22) that detects the pressure of the compressed air in the air supply flow channel. The annular recess (25) has a first section (25a) and a second section (25b) that is deeper than the first section, and the air supply flow channel is opened to the second section (25b).