The critical speed concept is introduced as a basis for circular saw design. The cutting behavior of a circular saw is shown to be a vibrational response to the applied cutting forces. Resonant vibration occurs when the saw rotates at a speed close to a “critical speed,” causing large lateral motions and “snaking” sawcuts. Saw tensioning is effective in increasing critical speeds by 20–30%. For a traditional collared saw, stable operation can be achieved up to 85% of the lowest critical speed. Guided saws are generally more stable and can operate super critically between the first and second critical speeds. This allows guided saws to have thinner kerf than equivalent collared saws.