Gas vs Corded vs Cordless String Grass Trimmers

Grass trimmers are used for precision cutting of grass that has been missed by mowers. Instead of steel blades, nylon string is used to cut the grass. This is safer and allows the cutting head to be partially exposed (a small guard protects the operator from stones that are flung up) to allow precise placement of the cutting head. Accidental damage to objects at the edges of the lawn (fences, trees) is also minimized. Protection (safety goggles, shoes, long pants, long sleeves) should still be worn at all times.

Popular brands include Ryobi, Echo, Homelite and Stihl.

Grass Trimmer String Feed Mechanisms

String feed mechanisms are a major source of user complaints.

Fixed cut-length trimmers are the simplest and most reliable. A short length of pre-cut string (typically 7 to 17 inches) is fixed to the cutting head. The ends of the string are gradually worn down cutting grass. When it is too short to cut effectively, the string is manually replaced.

Advantages

• Simple and reliable.

Disadvantages

• No automatic string replenishment.
• Remaining string stub is never used and is thrown away and wasted.
• String length cannot be gradually increased as the string is worn down.

Bump feed spool systems are more convenient but less reliable. Many yards of string are wound on to a spool, like on a fishing rod. Lightly tapping the cutting head on to the ground causes the spool to feed a few inches of line. On some models, turning the power off and on will feed more string. A line cutter blade at the end of the guard cuts off excess string if the string is too long.

Advantages

• Full use is made of available string. There is little wasted line except the stub at the end of the spool.
• String length can be continuously replenished as the ends are worn down.

Disadvantages

• Feed mechanism can jam or feed too much line.
• Replacement spools can be expensive. Bulk line (hundreds of yards) is cheaper but must be manually wound on to the spool.
• Excess lengths of string can be flung off by the line cutter at high speed and cause injuries.
• The line cutter sometimes doesn’t work and the excess line ends up hitting and damaging the guard.

Automatic feed spool systems are available on newer models. Advantages and disadvantages are similar to bump feed systems.

Additional advantage

• Automatic feed is convenient.

Additional disadvantage

• Spool can feed too much or too little, more so than for bump feed systems. A badly designed model can use up an entire spool to trim a small garden.

Gas Versus Corded Electric Versus Cordless Grass Trimmers

Grass trimmers follow the standard trade-offs between gas, corded and cordless tools.

Gas trimmers are the most powerful, available in up to 17 inch wide cutting paths. They are also

• Noisy.
• Heavy (8 to 13 pounds).
• Difficult to start and maintain.

Corded trimmers are inconvenient because of the cord and can be

• Light and weak (as low as 3 pounds, 2 amps at 120 volts, 9 inch cutting path).
• Heavy and powerful (as high as 10 pounds, 7 amps, 15 inch cutting path).
• Anything in between.

Cordless trimmers are convenient but

• Are heavier than corded trimmers.
• Lack power (7 to 12 inch cutting path) and are not suitable for weeds.
• Lack endurance (10 to 45 minutes).
• Need expensive replacement batteries after a few years.

The Best Grass Trimmer

Homeowners should choose the least powerful trimmer that will get the job done. Less powerful trimmers are safer, throwing stones and excess cut string with less energy.

Reliability problems continue to plague spool feed mechanisms. An Internet search should be made for user reviews of specific models.

Resources

• Corded Versus Cordless Electric Lawn Mowers