Flex coupling for grinders and chippers

A cutting machine and a method of using the cutting machine includes a cutting apparatus having a cutting device, a jackshaft sheave, an endless belt and an engine sheave. The cutting machine may have a jackshaft sheave, which is rotatably connected to the cutting instrument with the endless belt disposed about the jackshaft and engine sheaves. An engine includes a flywheel with an interface, which are configured for powering the cutting apparatus. A shaft assembly transfers energy from the flywheel of the engine to the engine sheave. The shaft assembly includes a shaft plate, a stub shaft and a coupling plate. The shaft plate is connected to the coupling plate and defines a shaft aperture with the stub shaft disposed in the shaft aperture. The stub shaft depends from the shaft aperture and is rotatably connected to the engine sheave. The coupling plate includes a coupling rotatably connected to the interface. The coupling defines a coupling chamber in which another end of the stub shaft depends and is connected in the coupling chamber such that a rotation of the coupling rotates the stub shaft to rotate the endless belt about the jackshaft and engine sheaves to operate the cutting apparatus.