40V 12" String Trimmer (Tool Only) - STF309

Auto-feed string trimmers use centrifugal force to release trimmer line. Each time the unit is activated, the spinning of the trimmer head exerts a force that unlocks the trimmer spool, allowing line to be released. A spring-loaded mechanism relocks the line after approximately 0.25” of line has been release. Therefore, every trigger pull will release line. Bump feed/ bump and feed string trimmers work with a similar mechanism, but the spool lock is manual disengaged by the user by “bumping” the trimmer head on the ground while the unit is in use. This mechanism provides operators with more control over how much line is used.

For attachment capable string trimmers, the following brands are compatible: Poulan Pro, Ryobi-Expand-it and Trimmer plus. If you are unsure if you have an attachment capable string trimmer unit, please contact us at 1-888-90-WORKS

Trimmer line will break off during use which is a normal occurrence. In harsher terrain or when used to edge, the string trimmer's line will break off more often as it makes contact with hard surfaces. To reduce line breakage here are some tips: • Keep the underside of the trimmer head/guard area clean of debris. • Ensure that the cutting blade is clean/clear, and the blade is exposed and shard enough to trim the line. This will also help to reduce excessive line breakage. • Avoid direct contact with hard surface areas when using the string trimmer. • In thicker, denser, and longer grass, you may want to go slower. Listen to the sound of the string trimmer, if it reduces speeds, or slows down too much, back away from the grass and start again at a slower pace.

No, string trimmers should never be operated without a guard. The guard is a safety feature and helps reduce debris such as grass clippings from being picked up and flung towards the user. It also has a cutting bar on it to prevent line from overextending and breaking off at large lengths. Operating without a guard will cause the string trimmer to work harder than it must and will reduce the life span of the motor. It will also void the warranty.

Line unraveling can be caused by winding the spool line the wrong way or simply not winding it tight enough. Please make sure you follow the guide inside your owner’s manual thoroughly as this process may take some time to correctly achieve.

A string trimmer that has a reduced gear motor does not directly drive the trimmer head. Instead, the motor drives a larger gear that is attached to the trimmer head. This reduces the speed of rotation but increases the torque. It allows a smaller, lighter motor to produce extra torque and perform tasks more efficiently, while ensuring that the unit is easy to maneuver.

Yes, all Greenworks string trimmers come with spool and line that has already been installed in your unit.

No, we do not advise using a thicker diameter line than what is advised in your owner’s manual. The use of a thicker line may result in over working the motor and could potentially damage the motor resulting in shorter life span of the unit. This will also void your warranty.

Yes, you can use any generic brand of trimmer line to rewind your existing spool. Please refer to your owner’s manual to ensure you purchase the correct diameter of line for your unit.

No, we do not offer this feature currently. However, we do offer attachment capable string trimmer units that can be used with a variety of different attachments from the following brands: Poulan Pro, Ryobi Expand-It and Trimmer Plus.