How Does a Wood Chipper Work?

Whether your goal is to clear away debris from trees or to make compost, a wood chipper can be an efficient way of mechanically cleaning up small limbs. Wood chippers come in many sizes, from large industrial types to smaller ones for the homeowner. But no matter their size, the mechanics of the wood grinders operate in the same way.

The Power Plant

All wood chippers must have some type of power input to turn the large grinding knives that perform the actual work of making the small chips. An electric motor or a fossil-fuel engine drives a set of knives. This power is transferred by a set of pulleys and v-belts, or a gearbox. The pulley-and-v-belt method uses a small pulley on the engine and a larger pulley on the blade shaft to regulate the speed of the rotating knives. A v-belt, much like the one in your car or truck, carries the power from the engine or motor to the shaft. A gearbox also transfers power to the cutters, but in way that is invisible to the eye. A series of gears are enclosed in the gearbox that regulate speed and power to the cutting box.

The wood chipper's cutting blades are the actual heart of the machine. The type of cutting blades will decide just how large a branch the machine can devour. Some chippers use very sharp blades that are attached on three or four rotating shafts, and which shave the sticks very quickly into smaller, elongated pieces. These shafts are in line with each other and quickly make the branches smaller and smaller with each pass against the sharp blades. Other chippers use inter-meshing blades that are able to pull the sticks into the cutting steel, making for a self-feeding type of wood chipper. The inter-meshing blades have a screen below the blades to maintain the size of the chips. The inter-meshing type of wood chipper will be slower, but the chip size will be consistent.

Wood chips can be used as a side dressing for flowerbeds and gardens. The wood chips can also be allowed to sit and break down (or compost) for addition directly into the garden bed. Not all species of wood should be used as compost or side dressing in gardens, as certain trees may contain chemicals that can be destructive to some plants. Check with the local extension agent if you have any questions regarding the type of wood chips to apply to a garden.