String trimmer

A string trimmer, also called a line trimmer or whipper snipper, is a powered handheld device that uses a flexible monofilament line instead of a blade for cutting grass and other plants near objects. It consists of a cutting head at the end of a long shaft with a handle or handles and sometimes a shoulder strap. String trimmers powered by an internal combustion engine have the engine on the opposite end of the shaft from the cutting head while electric string trimmers typically have an electric motor in the cutting head.

Also referred to by variations of the brand names Weedeater and Weedwhacker.

The head contains a safety sheild on the user side and a rotating hub which may also be called a head or spool.

When the hub spins at high speed the filament or filaments protruding from the hub creates a cutting disk with the most efficient cutting at the edge. Some small trimers have one filament while larger trimmers typically have two. As the filament wears away the diameter of the cutting disk decreases and therefore cutting efficiency decreases.

Newer string trimmers have a spool in the rotating hub that provides additional line. Usually tapping the rotating hub on a hard surface ejects more line and a blade on the safety sheild cuts the line down to a maximum length.

Safety

While the monofilament line may be slightly safer than a metal blade in terms of cutting, the open design can make it more dangerous than a modern shrowded lawn mower. The rotating hub has a tendency to grab clothing and other items similar to the dangers of a PTO and rotating the filaments tend to throw rocks and other hard items. Eye injuries are common for both users and bystanders. Users should always wear safety glasses. Hearing protection is required for almost all string trimmers. Closed toed shoes, long pants and long sleeves are recommended. The trimmer should be turned off or to idle when near bystanders without the proper protection. (Refer to the manufacturers manual for additional safety instructions.)

Use

The speed of the spinning hub is usually controlled by a trigger on the handle. A common mistake is to run the trimmer at full speed when near objects. High speed near objects tends to wear or break line and damage objects without working faster. Running at a slower rotational speed can actually increase the speed of the job by requiring less passes and less stops to reload line or untangle the hub. The speed should be varied depending on the nature of nearby objects. Also, at slower speeds the line will whip around thinner objects without grabbing, eliminating additional passes near objects like sign poles and chain link fences.

For vertical cutting the whole machine can be tilted or some trimmers allow the head to be adjusted at different angles. (Note: Vertical cutting is not recommended near sidewalks or other concrete and pavement edges. It leaves open groves that allow water to collect and cause damage.)

Accessories

Many string trimmers allow the hub, the head or the lower part of the shaft to be replaced with accessaries. Common accessories include:

• replacing the monofilament line with metal or plastic blades.
• replacing the lower shaft with a small chain saw to create a powered pole saw.
• replacing the lower shaft with a hedge trimmer.
• replacing the lower shaft with a cultivator.
• replacing the head with a blower.