Machine tools

A machine for machining sheets, in particular for cutting out by milling metal sheets which can be cut singely and when stacked one on top of the other, comprising a rotatable machining head, a support to which the machining head is attached, an arrangement for compressing the sheets to be machined which arrangement is adapted to carry out a rotary movement during use of the machine about a longitudinal axis which is in alignment with the axis of rotation of the machining head, the arrangement comprising at least two rollers for bearing against the sheets during machining and each rotatable about a transverse axis perpendicular to said longitudinal axis, at least two guide posts on which the rollers are respectively mounted, and compression washers for resiliently biassing the rollers against the sheets, a rotatable toothed ring on which the arrangement is mounted by means of said guide posts, which ring has a longitudinal axis in alignment with the axis of rotation of the machining head, a pinion meshing with the toothed ring, a motor for driving the pinion and thereby the ring and the arrangement, angular control means which can be driven by the motor via reduction gearing in the same reduction ratio as the arrangement and which are electronically controlled whereby it is possible to control the angular position of the arrangement as required so that the said axis of rotation of the rollers can be orientated, in use, perpendicular to the direction of the machining line, when straight, and perpendicular to a tangent of the machining line, when an arc, and programmable electronic means for said angular control means which operate with reference to the angular position of the machining head.