A circular saw for re-sawing or ripping lumber, timber or like wood, such as logs, blocks, cants and boards, into thinner pieces. The saw includes a plurality of saw blades (9) which are mounted on a saw axle (4) and dogged by the axle as it rotates, a drive motor (1), and power transmission means mounted between the motor and the axle. The transmission means includes a belt (23), chain or like device which passes in a loop around two wheels (24, 25) of which one is intended to be driven by the motor and the other is intended to drive the saw axle. The transmission ratios between the wheels (24, 25) and respective wheel axles are mutually different and the wheels and their respective axles are mounted in a separate holder device (28). The holder device can be mounted with a selected wheel coupled to the drive motor (1) and the other wheel coupled to the saw axle (4) such as to cause the saw blades (9) to rotate at one or the other of two predetermined speeds in the performance of a cutting operation.