US Patent 7273335 Machine tool

A machine tool includes a table supported by a bed for forward and rearward movement along a path of movement, left and right transversely aligned upright columns on opposite sides of the path of movement, a cross rail supported in the columns for movement upwardly and downwardly along forward and rear guide rails on inwardly facing column surfaces, a spindle head supported by the cross rail for movement leftwardly and rightwardly. The cross rail, the left and right columns, the spindle head and the guide rails are symmetrically positioned from front to rear and vertically by vertical or horizontal symmetry defining planes so that heat generated creates balanced self-cancelling forces.