Inverted vertical lathe

摘要

The object of the invention is to provide an inverted vertical lathe comprising a device for replacing collets automatically, and having a detector for detecting that the collet has been gripped correctly. A chuck 400 mounted on a headstock 40 grips a collet 500 in a replaceable manner via a tapered bore 430 provided to the end thereof. A collet end face eccentricity detector 600 comprises a detecting member (sensor) 610 fixed to the end of an arm 630. The detecting member 610 detects the eccentricity of the end face 510 of the collet 500 in a contactless manner. A variation pattern of the eccentricity occurring when each collet 500 is gripped correctly by the chuck 400 on the main spindle is detected in advance, and this pattern is compared with the variation pattern of the eccentricity detected by the present detection, and thus, whether or not the collet has been gripped correctly is detected.