Selecting And Using A String Trimmer

Richard L. Parish  |  12/11/2004 12:54:37 AM

String trimmers are an essential tool for grounds maintenance professionals and for most homeowners who maintain their own lawns.
The advent of string trimmers more than 30 years ago revolutionized turf maintenance and made other methods of trimming turfgrass obsolete. You have many choices in selecting a string trimmer.

Electric or Gasoline Engine
Many small homeowner string trimmers are powered by an electric motor. In most cases, these machines must be connected to a 120-volt outlet with an extension cord, although a few battery-powered models have been introduced. The advantages of the electric models are simplicity and low maintenance. There is no need for gasoline, or mixing gasoline and oil, and no engine to maintain - or try to start. The electric models are also quieter.

The major disadvantage of an electric unit is the need for an extension cord, which is a nuisance to maneuver and limits your range. The electric units also are less powerful than some of the larger gasoline engine models. A gasoline engine gives you complete freedom to roam without an umbilical cord.

Straight or Curved Shaft
String trimmers generally have the engine at the upper end of a metal tube and the cutting head at the other end. A flexible cable running inside the steel tube connects the two. On many smaller machines, the tube is curved near the cutting head (Figure 1). Heavier duty models, including most professional models, use a straight tube. These two styles are usually referred to as curved shaft or straight shaft even though it is the tube that is straight or curved and the shaft, which may be a flexible cable, is inside.
The straight tube models require a bevel gearset at the head to change the direction of rotation. Straight shaft models may be more durable since the drive cable does not have to flex as much. Some users prefer the shape and angle of one style over the other, but this is subjective.

Homeowner and smaller professional string trimmers generally have a single C- or D-shaped handle for one hand and the operator’s other hand grasps the tube. On larger professional models, a wide "bicycle-type" handle is used (Figure 2). On those models, the trimmer is suspended from the operator’s shoulders on a strap; the operator grasps the two hand grips at the ends of the handle to control the position of the cutting head. The "bicycle-type" handle provides better control and is the only type of handle that should be used with a brush-cutting blade.

Cutting Heads
The standard cutting head on most units feeds out two pieces of plastic line. Bump-feed heads are popular. With these, you just bump the head on the ground to feed out more line, and the line is automatically cut to length. Some models have manual heads that require you to pull out the line manually. A few models used fixed-length pieces of line that must be inserted individually. Some small string trimmers have only one line. Most heavy-duty professional trimmers allow the substitution of a blade for the string head. The blade may be an X-shaped steel blade for light brush or a saw blade for larger brush (Figure 3).

Weight and Power
Weight and power increase together. The more powerful professional models are heavier than light-duty homeowner models. Some string trimmers are now available with 4-cycle engines, developed to reduce emissions.

A string trimmer is a useful addition to almost any gardener’s toolshed. The light-duty electric models are easier to maintain, but gasoline engine models eliminate the hassle of dragging around an extension cord. The biggest maintenance task on most models, electric or gasoline, is replacing string. Prices of light-duty gasoline models are comparable to some electric models. Most homeowners will not need a professional trimmer with brush-cutting capability.

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