A machine tool (1, 100) comprises a support structure (4, 104) and a machining head (8) bearing a mandrel (12). The machine further comprises at least one action device (20) contained on the support structure (4,104) and applied to it, which generates pushing or pulling actions on said support structure (4, 104) acting against the action of the weight of the head (8) thereon.

An air balance mechanism includes a plate part, fixed shafts, and movable cylinders. A flange is provided at one end of each of the fixed shafts. The movable cylinders are movable relative to the fixed shafts. A space is formed below a lower surface of the flange. Further, the air balance mechanism includes fixing bolts and adjusting bolts. The fixing bolts fix the flange and a plate part at positions different from the space. The adjusting bolts are inserted into the plate part through the space for allowing the postures of the fixed shafts to be adjustable.

An air balance mechanism includes a plate part, fixed shafts, and movable cylinders. A flange is provided at one end of each of the fixed shafts. The movable cylinders are movable relative to the fixed shafts. A space is formed below a lower surface of the flange. Further, the air balance mechanism includes fixing bolts and adjusting bolts. The fixing bolts fix the flange and a plate part at positions different from the space. The adjusting bolts are inserted into the plate part through the space for allowing the postures of the fixed shafts to be adjustable.

A counterweight mechanism for a swivel arrangement includes first and second counterweights each including a seat, an axle, and two cylinders. The swivel arrangement has one end adjacent to the axle. The axle is rotatably, partially disposed in the seat. Each cylinder has a first end pivotably secured to a position proximate to the axle and a second end pivotably secured to the seat.

A numerical control machine-tool includes: a ground-resting base plate; a movable supporting column rising cantilevered from the base plate in a substantially vertical direction and movable horizontally on said base plate; a first electronic-controlled drive assembly for moving the supporting column along the base plate; a head-carrier slide fixed in vertically sliding manner in a straight longitudinal slit extending along the front face of the supporting column parallel to the longitudinal/vertical axis of the supporting column; a second electronic-controlled drive assembly for moving the head-carrier slide along the supporting column; a straight supporting beam inserted in an axially sliding manner into the head-carrier slide and cantilevered juts out from the front face of the supporting column while remaining substantially parallel to the ground; and a third electronic-controlled drive assembly for moving the supporting beam forwards and backwards with respect to the head-carrier slide parallel to the beam longitudinal axis.