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An edger (also known as a lawn edger or stick edger) is a garden tool used to cleanly separate a lawn from a walkway or other paved surface, such as a concrete sidewalk or asphalt path. Edgers may be manual or automated, typically employing a small gasoline (petrol) engine or an electric motor, while newer gas-powered models have four-stroke engines. An edger enables a user to create a clear separation between the lawn and the walkway. It helps to impart a finished appearance that is neater than can be achieved by merely mowing over the border of the lawn and walkway (which frequently permits tufts of low-growing grass to hang over onto the walkway, resulting in an irregular or ragged appearance).
In operation, a manual edger usually includes a broad hemispherical blade attached to an elongated handle, which the operator uses to drive the blade into the turf directly alongside the hard surface. In addition, the blade may have a flat top to allow the operator to step on the blade, driving it deep into the lawn and turf in order to clear a space between the lawn and the hard surface. In contrast, powered edgers may operate on any of a variety of methods, such as rotating wheel blades or thrashing wheels, which also operate to define a clear separation between a lawn and a hard surface.
A basic gasoline lawn edger consists of an engine, belt tensioner, pulleys, and a blade. Most lawn edgers incorporate a belt and two pulleys (one on the engine and the other on the blade head) and a belt tensioner used for going deeper into the grass and gaining more RPM. Some gasoline edgers also have a device called a "robot head," used for adjusting the pitch of an edger head between the horizontal and the vertical. Some edger brands, such as King O' Lawn, have a blade clutch to avoid the user pulling up on the belt tensioner to stop the blade (usually a small lever that can be pulled up with the operator's foot). The drive system on a common edger is a belt drive from the two pulleys. Husqvarna uses a worm gear shaft drive system. One disadvantage to the shaft drive system is lower engine power. A chain drive would be ineffective and cause damage to the blade, sprocket, and engine if a solid object was hit. One advantage to the belt drive system is that the belt will skip when hitting objects. The blade on an edger is usually made from cast steel.
The gasoline lawn edger was invented by Louis Faas Sr. of King o' Lawn Inc in the 1940s. The first gasoline edgers used a Briggs & Stratton 1.5 horsepower (1.1 kW) engine. Using just basic components, the first edgers were very basic with a very small engine. Brands such as McLane and Cooper Klipper would follow several years later.
Most gasoline edgers use a four-stroke engine with 2 or 3.5 horsepower (1.5 or 3 kW), although some early edgers used a 1.75 horsepower (1.3 kW) engine. Some modern gasoline edgers use engines ranging from 3.5 to 4 horsepower (2.5 to 3 kW), and some economy edgers use a two-stroke engine.
Cordless and corded electric edgers are also available in a range of motor power levels.