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Use a String Trimmer

string trimmer

A fresh-cut lawn always gives your landscape a first-class look, and a little trimming around the edges can make it look even better. Using a string trimmer around the yard is an easy way to get professional-looking results.


man trimming his lawn

The important first step in using a powered string trimmer is to carefully read the owner’s manual. If a copy isn't available, visit the manufacturer’s website for instructions. Become familiar with the controls, safety features and verify that guards and attachments are properly secured. Selecting a powered string trimmer is relatively easy with the following guidelines.

  • String trimmers are powered either by gasoline engines or electrical motors.
    - Gas engines are either four-cycle (larger with more power) or two-cycle (smaller and easier to handle). They typically have a cutting width of 16 inches to 18 inches and use heavier, single-strand monofilament line.
    - Electric-powered string trimmers can be corded (requires an extension cord) or cordless (battery powered). They typically have a cutting width of 12 inches to 15 inches and use 0.080-inch monofilament line wound onto a spool.
  • Replacement parts include air filters, spark plugs or monofilament line or spools. Make sure the replacement spool fits the trimmer brand and model.
    - The monofilament line on a string trimmer is capable of throwing objects, so make sure the safety guards are in place and everyone stands back when the trimmer is running. Be especially sure that children and pets aren’t near the work area.
    - Also, keep the line from making contact with concrete, asphalt, rocks or utility lines, such as landscape lighting wires. Be careful operating a trimmer around plastic lawn sprinkler heads or vent pipes that can be damaged.
For safe operation of a powered string trimmer, wear closed-toe shoes, long sleeves, long pants, gloves, ear protection and safety glasses.

String Trimmer Operation

Step 1

To start a gas-powered string trimmer, slowly pump the primer bulb (as recommended by the manufacturer) to feed fuel to the carburetor.

Step 2

Turn on the choke.

Step 3

Place the trimmer head on the ground, hold the throttle and pull on the starter rope to start. (Some models have an ON button and starter).

If the engine doesn’t start within three to five tries, let it rest for 30 seconds, then pull the rope again. Some trimmers use an electric start adaptor: Plug in and press the START button.

Step 4

Once the trimmer is running, adjust or turn off the choke.

Step 5

Pick up the unit with your right hand near the throttle and your left hand on the assist handle. Hold the throttle for about 30 to 60 seconds to let the engine warm up.

Step 6

When cutting, keep the power unit at waist level with the attachment parallel to the ground.

Step 7

Follow the manufacturer’s recommendation as to which direction to work the trimmer — from right to left or left to right. This will depend on which way the trimmer head spins. Most heads spin clockwise, meaning you would work from right to left.

  • Slowly move the trimmer from side to side or in and out of the cutting area, allowing the tip of the line to do the cutting.
Don’t force the trimmer to make heavy cuts as they can overload the engine. Thicker and tall (over 8 inches) grass should be cut in smaller increments to avoid premature line wear.

Step 8

Keep moving along the lawn edge, cutting to the lawn height.

Watch ahead to where the trimmer will cut next to make sure it doesn’t cut decorative plants or other yard objects.

Step 9

Periodically check the length of the monofilament line.

  • Some trimmers have spools with an automatic line feed that uses centrifugal force to advance the line.
  • Other trimmers release additional line when the trimmer spool is tapped on the ground or bumped. (The attachment shield will cut off the excess.)
  • Larger trimmers require that the trimmer be stopped to replace shorter, heavier line if it is damaged.
It’s a good idea to have extra line on hand. This can save you a trip to the store in the middle of a job.

Step 10

Some trimmers can be used as an edger to cut sharp edges around beds or curbs. Turn off the unit, rotate the head (or handles on some units) and use it as a lawn edger. Some units require an edger attachment. Cultivator and hedge trimmer attachments also are available for some models.

Step 11

When the trimming job is finished, release the throttle and let the engine idle for a few seconds. Then press and hold the OFF or STOP control switch until the unit completely stops.

String Trimmer Care

trimmer care

Let the trimmer cool down before storing. To clean the machine, use a brush to remove clippings and debris. Don't spray the unit with water or other cleaners as they may damage it. Store a string trimmer somewhere dry and out of reach of children and possible damage.

Maintenance is an important part of relying on a string trimmer for many years of service. Check the owner’s manual for the suggested maintenance schedule. To maintain a gas-powered string trimmer:

  • Check the condition of the line, blade or cutting wheel before every use.
  • Fill the fuel tank and check the oil before every use.
  • Check and refill or replace the cutting line as needed before every use.
  • Change the oil (four-cycle engine only) and clean the spark plug arrestor after the first 10 hours of use, then every 25 hours after that.
  • Check and re-oil or replace the air filter every 10 hours of operation.
  • Check the spark plug condition and verify the gap every 25 hours.