Instead of using blades to shred materials, grinders are able to reduce hard, strong material like wood, plastic, clay and shale into powder, dust or shavings by using a high pressure hopper or series of rollers. Because they are mostly employed for large, heavy duty applications, grinders are rarely found anywhere but industrial environments.
Grinders are used in furniture companies, cabinet manufacturing, construction supply companies, sawmills and dimension mills to reduce scrap wood for recycling purposes. Scraps, stumps, chips and shavings are all fed through a grinder to become uniform sawdust that is used as animal bedding, compost and roofing paper. These industrial grinders are called tub grinders, which strictly work with wood and organic material. Other grinding applications besides waste reduction include recycling, land clearing, construction and demolition.
An industrial grinder either has horizontal or vertical orientation, and one or more feeding shafts. An auto drive hopper made out of steel presses the material against a blade. The grinder is powered by an electric motor, while the hopper is powered hydraulically. Depending on the size of the material and the desired rate of grinding, grinders have varying horsepower.
The largest grinders are able to produce 600 or more yards of shavings per hour, while standard grinders produce anywhere from 40 to 100 yards. The particle size of the shavings, powder or dust also varies, depending on mesh size of screens through which the material must pass. Particles that are too large are fed back through the grinder a second time until they have reached the desired size.
Tub grinders, used for wood recycling, use a hammer that rips and tears large pieces of wood and pulls them below the tub floor by forcing them through small openings in grates. When looking for a new grinder, considerations should be made for how much material will go through the grinder, how large the finished product should be, and whether it will be relocated often. Some grinders are made for warehouse settings, while others are mobile and able to travel over rough forest terrain.