Abstract: A lathe comprising first and second headstocks having respective rotatable spindles carrying a respective workpiece gripping devices, the second headstock being presented towards the first headstock, and being relatively movable towards and away therefrom so that a workpiece gripped by the gripping device of the first headstock can be transferred to the gripping device of the second headstock. Movable tool carrier means associated with the first and second headstocks, whereby machining operations can be performed on workpieces held in the gripping devices of the first and second headstocks, and there is means for monitoring the angular positions of the spindles whereby rotational datum positions of the spindles can be established.