Patent ID: 7997838

Claim:
A main tool spindle device comprising: a housing having an air supply passage therein to which an air supply source is connected; a main tool 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 an inner surface of the housing on a front tool 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, wherein a first outer-side circumferential air receiving groove is formed on an outer circumferential surface of the air sealing member at a position at which air is supplied through the air supply passage in the housing, and wherein a plurality of communication holes or slits are formed in the air sealing member all around the periphery thereof, the plurality of communication holes or the plurality of slits passing through the air sealing member from the first outer-side air receiving groove to the inner circumferential surface of the air sealing member.