Main spindle device

A main spindle device comprising:

• a housing having an air supply passage therein to which an air supply source is connected;
• a main spindle that is inserted into the housing and supported by a bearing so as to be able to rotate relative to the housing;
• and
• an air sealing member that is positioned between an outer circumferential surface of the main spindle and the housing on a front side with respect to the bearing along a rotation axis of the main spindle, has a substantially annular shape, and is detachably fixed to the housing with an inner circumferential surface of the air sealing member facing the outer circumferential surface of the main spindle,
• wherein air supplied from the air supply source through the air supply passage is discharged into a gap between the outer circumferential surface of the main spindle and the housing, thereby effecting non-contact air sealing at least between the inner circumferential surface of the air sealing member and the outer circumferential surface of the main spindle.