Easy access to the shredding chamber also makes it simpler to service the chipper knife and flail blade. The clutch of a chipper-shredder is similar in function to a clutch found in a car or lawn tractor. It engages and disengages the rotor that holds the shredding and chipping blades. Idler-lever clutches include a lever that you use to engage the shredding mechanism. They are relatively simple controls that give you more control over the chipping or shredding.
Centrifugal clutches engage or disengage automatically, depending on engine speed.
For example, if the shredding assembly bogs down, a centrifugal clutch will automatically disengage, giving the engine time to increase power. This means the user has less control, and these machines are harder to start because you must crank the engine and shredding-chipping mechanism at the same time. On the other hand, direct-drive machines are usually less expensive. This holds the shredding hammers and chipper blade or blades. On direct-drive machines, the rotor is fitted directly onto the engine's crankshaft, which puts an extra load on the engine's main bearings.