Mechanical trench diggers work by using a chain and auger to dig a narrow trench a few feet deep. Diggers on wheels move forward and backward to make a trench as long as needed, while the operator moves the chain and auger unit up and down. The auger uses curved teeth to push dirt to the side of the trench, which prevents the trench from filling back in with dirt.
The key is to coordinate movement of the wheels with the chain and auger. Similar to a chainsaw that creates sawdust, the rotation of the augers creates ultra-fine dirt. The chain starts first while the wheels are in neutral. Lower the digging system into the ground to start a narrow trench. The chain and auger are controlled through throttle and transmission controls. Wheeled trenchers move backwards when they dig.
When the chain and auger digs deep, wheels are locked to prevent sideways movement. Large rocks hit by the augers may shake the trencher. The unit does not move when the wheels are locked in place.
Types of mechanical trenchers include walk-behind trenchers, bed edgers, wire trenchers, and ride-on models. Larger units are faster, dig deeper and take more skill to handle. Bed edgers are ideal for placing rocks on landscaping projects. Wire trenchers dig a trench and lay electrical wires simultaneously.