Difference Btw Automatic, Semi Automatic and Bump Feed Trimmers

So are you interested in an electric string trimmer? Would you like to learn more about the difference between automatic, semi-automatics and bump feed trimmers? Are you stuck when choosing between these three? If so, you’re in the right place.

Automatic, semi automatic and bump feed trimmers have their own advantages and disadvantages. The automatic trimmer automatically advances the string without requiring you to tap it whereas the semi automatic requires you to stop and restart the trimmer and the bump feed trimmer requires you to tap its head manually every now and then to advance its string.

Automatic, Semi Automatic and Bump Feed Trimmers

Automatic String Trimmer

Just as the name suggests, an automatic string trimmer ensures automatic advancement of the string as soon as it gets short. The trimmer’s mechanism immediately advances the string using centrifugal force. This makes it extremely easy to focus on your trimming and edging without worrying about introducing new line.

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You don’t have to stop and restart the trimmer or tap the unit manually like you would have to with the bump feed trimmer thereby helping you finish your trimming and edging faster. A really good example of an automatic string trimmer that works very well is the Black and Decker LST136.

Pros of Automatic String Trimmers:

– One of the main advantages an automatic string trimmer offers is that it allows you to focus more on your trimming. You can focus on the grass and other landscape elements without having to worry about the length of the string being too short.

Automatic vs Semi Automatic vs Bump Feed Trimmers

– The automatic string advancement system allows you to get your work done a lot faster than you’d be able to with a semi automatic or bump feed string trimmer.

Cons of Automatic String Trimmers:

– All string trimmers are subject to wear and tear regardless of whether they’re automatic, semi automatic or bump feed. The auto feed trimmers can be temperamental at times and could cause occasional problems. Fixing an automatic feed trimmer on your own isn’t easy. There’s always a chance of the line feed jamming every now and then. In that case, it may be difficult for you to fix and get the trimmer running again.

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Semi Automatic Feed Trimmers

These types of trimmers also ensure that your line is kept at the required length but it requires you to stop and then restart the trimmer. The line will then advance about ¼ inch each time you stop and restart. The Earthwise LST10012 is a good example of a semi automatic feed system.

Pros of Semi Automatic Feed Trimmers:

– A major advantage of this type of feed system is that introducing new line is as easy as stopping and restarting the trimmer. A fresh length of line is produced to ensure trouble free trimming and edging.

Cons Semi Automatic Feed Trimmers:

– The major disadvantage of this type of feed is that the line will be advanced every time you stop and start the trimmer whether it is required or not. Many users dislike this type of feed as it wastes line by cutting off the excess length.

Bump Feed String Trimmers

Bump feed trimmers require you to manually bump the head of the trimmer against a flat surface. This result in new string being released which you can use to cut down more grass or weeds. The manual action will require you to stop trimming every now and then to tap the head of the trimmer to get a new length of line. A prime example of a bump feed system that works really well is the GreenWorks 21142.

Pros of Bump Feed String Trimmers:

– One of the main advantages of a bump feed trimmer is its simplified system. Unlike an automatic or semi automatic feed system the bump feed trimmer is extremely easy to fix if it fails. In many cases, you’ll be able to figure the problem and solve it on your own. Usually the cause would be your line jamming which is really easy to fix. But it isn’t the case with an automatic trimmer or semi automatic trimmer.

Bump Feed String Trimmers

– Another advantage with the bump feed is that it gives you control over how much line you use. You only use the string as needed when it gets short. You just have to tap its head for a new length of string to be introduced.

Cons Bump Feed String Trimmers:

There’s a chance of your bump feed trimmer being damaged if you tap its head too hard. Tapping the head harshly can cause damage to the spring or the spool. Therefore, it’s extremely important that you’re very gentle when using a bump feed trimmer and only tap on grass and not hard surfaces.


The best string trimmer for you mainly depends on what your needs are. We have discussed above the difference or Automatic vs Semi Automatic vs Bump Feed Trimmers. If you’re someone that’s interested in speed and ease, the automatic or semi automatic feed system is your best choice. But if you’re looking for a dependable trimmer that you can easily fix (if it ever fails) and want more control over how much line you use, the bump feed is the way to go.

| About the Guest Author:

Guest Author
 Karen Neilsen is an enthusiast person who love writing about the String trimmer on Hub names. 

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