How Does A String Trimmer Work?

Parts of a String Trimmer

In order to properly understand how a string trimmer works, you need to be aware of the different parts of the machine and what role they play. We’re going to take a look at the different parts of a string trimmer and see what they do.


The motor is the powerhouse of a trimmer. This provides power to the spinning rotor that houses the string that cuts the grass.

There are two main types of motors that string trimmers have. Both of them offer their own capabilities and depending on what they are able to do, you should make the decision of going for either one.


Gasoline powered string trimmers use a mixture of gas and oil to power an engine, which provides power to the motor. They make a lot of noise but are very powerful. This makes them capable of dealing with heavy shrubbery and overgrown areas like tall grass. Gas trimmers are more expensive and heavier than the electric ones.

Electric Trimmers

Trimmers powered by electricity are quieter and less powerful than the gas ones. They require an electrical connection to power the spinning rotor but they don’t provide as much power as a gas trimmer. They are also incredibly light in comparison to gas trimmers, which make them more maneuverable. Electric trimmers are also cheaper than gas trimmers.


There are electric trimmer models, which are powered by rechargeable batteries. Electric trimmers that use batteries are easier to maneuver because there is no longer a cable involved to limit the movement, however it is possible for the battery to go flat before you’ve finished your trimming job.


The next part that you need to know about in order to understand how a string trimmer works is the shaft. The shaft is what connects the motor to the spinning rotor at the end of the string trimmer. The motor turns the internal mechanism of the shaft, which transfers that energy to the spinning rotor. There are two types of it – curved and straight. Read this article to find out more about this feature.

Cutting Head

The cutting head on a trimmer houses the monofilament line, which cuts the grass. It can house a light gage line or a heavier gage line. When the motor provides the shaft power, the shaft transfers the energy to the cutting head, which rotates to cut the grass when it comes into contact with the line.

Safety Features

Ensuring your safety is imperative for understanding how a string trimmer works. Without safety features, a string trimmer (even an electric powered one) can be dangerous for you and others around. A majority of string trimmers in the market employ safety features.

The first and foremost feature is a safety guard around the cutting head. This is pretty much the only dangerous part of the string trimmer. The safety guard around the cutting head protects you from coming into contact with the string trimmer while using it. It also helps to give direction to the debris away from you as you cut the grass.


A string trimmer is a wonderful tool. It is versatile, maneuverable and useful for all kinds of jobs in your yard. It can get into places where a lawn mower doesn’t and if you use it right, it can provide an excellent finish. Check out our reviews on some of the top string trimmers on the market if are looking to buy one.

DID YOU KNOW? You can also use a string trimmer to edge your lawn!

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