Nylon String Trimmers and Brush Cutters

The nylon string trimmer ranks with the lawn mower and rotary tiller as a major time-saving gardening tool: A grass- or weed-trimming job that takes half a day by hand can be done in half an hour or less with this power tool. While it was designed for trimming, it can also be tilted for edging along walks or garden beds.

The trimmer cuts by the rapid whirling action of a motor-driven nylon string. This method has a great advantage over such hand tools as grass whips or sickles: You can cut right against walls. When the flexible nylon filament strikes an obstruction, it does not break but merely wears away. When this happens, more nylon can be fed out.

These versatile, lightweight tools are run by battery, electricity, or gas-powered engines. A nylon string trimming attachment is also available for some small chainsaws.

Gas-powered brush cutters do regular trimming and also provide you with the option of replacing the nylon spool with blades for cutting light brush or tree limbs. Unless you have a lot of brush to cut, you probably won’t need this version.


Which type and size to choose depends on what you’ll need to do with it. If you have a large lawn or garden that demands a variety of cutting chores, start out by renting or borrowing a trimmer. If it won’t easily handle your toughest weeds, you need a more powerful model.

Power is determined by the size of the electric motor or the two-cycle gasoline engine. Electric models range from 1/8 to about 3/4 horsepower. Gas-operated models are rated by the size of the engine in cubic centimeters (cc). A 20- to 25cc engine will handle most heavy trimming or brush cutting work, even on a large estate, but to be sure that this fits your needs, rent one and try it out.

The width of the cutting swath is directly related to the power of the engine. The swath ranges from about 7 inches for the battery-operated or small electric trimmers up to about 20 inches for the large, gas-powered types. Any attempt to increase the nylon whip length beyond its rating will unnecessarily strain the engine.

Select a model that has an automatic or semiautomatic feed system for the nylon whip. Trimmers with these systems contain a spool of nylon filament in the cutting head. Lengths are fed out in either of two ways: automatically, by a sensor in the cutting head that automatically keeps the nylon at a certain length, or semiautomatically, by your rapping the base of the cutting head on the ground to release about 1 inch of nylon whip at a time. A knife edge in the rear guard trims off the frayed end and prevents too much cord from being put out.

Some other models require you to stop the engine and replace the whip by hand each time it wears down. This is time-consuming and frustrating when you are working in dense weeds that quickly wear away the nylon.

Spools containing up to 50 feet of nylon can be bought from trimmer dealers. On some models, two to four whips extend from the spool, offering greater cutting capacity. The nylon comes in different gauges, ranging from the small .051 up to the heavy 130. The smaller the motor or engine, the smaller filament you must use.

On the most popular models, the motor or gas engine is at the top of the handle and a long drive shaft inside the handle is attached to the cutting head. On others, the engine is mounted directly on the cutting head, which eliminates the problems that may come with a long drive shaft; however, because the engine is closer to the ground, the air filter may get clogged with dust or debris.

The handles (and, in the case of those with top-mounted engines, the drive shaft) are either straight or flexed (curved). A straight drive shaft has a more efficient design; therefore it normally is used on heavy-duty trimmers and on the majority of brush cutters.

For your own comfort, a trimmer should be balanced, particularly if you might use it for several hours at a time. Before buying, check the balance by holding each model as if you were using it. A few models have handles that can be adjusted in length according to your height.

If you choose a brush cutter, be sure the blades can be easily interchanged. At least two different blades should be available, one with 4 to 8 teeth for whacking off light brush and heavy weeds and another with 40 to 80 teeth for cutting small brush and limbs.


Always wear sturdy shoes or boots when using a string trimmer or brush cutter. Also wear goggles—a brush cutter tends to throw materials as it cuts.

Battery-Operated Trimmers

These, the smallest of the trimmers, are handy for light trimming and edging around a small yard. The battery, which provides power for about 45 minutes of trimming, will recharge when plugged into a standard 110-volt outlet over a 24-hour period. The cutting swath on battery trimmers is usually about 6 to 8 inches wide. Usually, the nylon string is advanced semiautomatically by tapping the base on the ground. There are also models with manual advance.

Electric Trimmers

These least-expensive trimmers will handle small to medium trimming work within 50 to 100 feet of an outlet. They are lightweight and quiet, with cutting swaths that range from about 7 to 18 inches wide. Models come with both automatic and semiautomatic nylon line feed.

The horsepower on electric trimmers usually ranges from 1/8 to 3/4. When operating an electric trimmer, do not let the motor strain and “lug down” during heavy cutting, or it will overheat and possibly burn out. Keep the motor running at high revolutions, and move slowly in dense weeds or grass.

Some models have a switch to reduce the power consumption when doing light trim work. This power reduction also helps extend the life of the motor.

Gasoline-Powered Trimmers

If your trimming chores are more extensive than you can handle comfortably with a battery or electric-powered machine, the gas-powered trimmer is for you. There are many options available in the cutting swath, the nylon cord feed system, and in the engine size, which ranges from 14 cubic centimeters to 30 cubic centimeters.

Choose according to the size of the job and your own convenience. The main disadvantage of this trimmer is that its gas engine needs more maintenance. It is also quite a bit heavier than the other types. Even if you are very strong, you’ll probably have to rest after 20 or 30 minutes.

Gasoline-Powered Brush Cutters

The brush cutter can do all that a gas-powered trimmer can, plus accept steel blades for chopping brush and tree limbs. Brush cutters have heavier drive shafts to accommodate the steel blades. Both the brush cutter and the trimmer are powered by two-cycle engines ranging in size from about 14cc to more than 30cc for the largest professional models. The largest ones have the engine set in a backpack on anti-vibration mountings.

Brush cutters are significantly more expensive than gas-powered trimmers. Be sure you have enough brush to warrant the additional investment.


Some brush cutters now being made have plastic blades that can be thrown away and replaced when worn. The metal blades can be sharpened with a second file.

Motors for battery and electric trimmers are basically maintenance free (see Maintaining Electric Tools). Maintain and tune the engines of gas-powered trimmers as detailed in About Gasoline Engines. Many of the newer trimmers have solid-state electronic ignition systems that do away with the need for periodically changing the points and condenser.

On gas-powered models, the air filters should be checked and cleaned regularly, particularly if the engine is mounted on the cutting head, where it receives much dust and debris. A clogged air filter not only reduces the engine’s performance but will soon cause engine damage.

The shaft of the trimmer is usually a flex wire rope-type shaft and should be oiled regularly.