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How to avoid line-feed problems

By Adele Dyer

The most common complaint about grass trimmers is how often the line breaks. Which? shows you how to avoid this and solve other trimmer problems. 

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In our tests we deliberately hit the grass trimmer's line on a metal edge to see how often the trimmer loses the line. This way, we can find those grass trimmers that will quickly spool out more line and those that will have you fiddling around for ages to repair a broken line. 

Top tips to avoid grass trimmer line-feed problems

  • Keep the head of your trimmer as clean as possible. Dirt and cutting debris can easily build up in the head and clog up the line-feed mechanism.
  • Keep plenty of line on the trimmer head. Don't worry that your line is too long - the trimmer head has a blade that will cut off any excess so it's the optimum length.
  • Remember that most automatic line-feed trimmers release more line when you start the grass trimmers. So each time you take your finger off the trigger and depress it again, more line will feed out. As you will naturally do this many times as you trim, there should be no need to worry about having enough line.
  • Automatic-feed trimmers often have a manual-release button. If the trimmer isn't pushing out more line automatically, it could be that the cord is slightly tangled up inside; the manual-release button means you can pull more line out past the problem.
  • If you buy line, rather than full replacement spools, make sure you wrap it very carefully without crossing the lines. If you don't, it could easily lead to a jam and the line being lost, as the trimmer can't feed out any more.
  • Look for a trimmer with thicker line - if it looks twisted, like a liquorice string, then it's usually a more heavy-duty line that's less likely to break. Line is marked by its diameter in mm, so look for line that's at least 1.2mm.
  • If you can, avoid hitting the line on fences and metal edging. This will break off chunks of line and the trimmer might not push out new line quickly enough.
  • A trimmer with one line is generally easier to thread than a trimmer with two - or, for the ultimate convenience, try a trimmer with blades.
  • If you're trimming for a long period of time, the spool might get hot, causing the line to stick together and not feed through properly. Take a break and let your trimmer spool cool down to avoid losing your line.
  • Some grass trimmers use plastic blades rather than line. The blades are cheap to buy and easy to replace on the trimmer head when they become worn. These models aren't designed for cutting long grass.

How to cut lawn edges

Start by adjusting your grass trimmer so you can comfortably hold and control it when cutting a vertical edge. Rotate the head to cut vertically, adjust the shaft length if necessary, as well as the position of the handles. 

Stand so that you can clearly see where you're cutting. Try to look along the length of the lawn edge to avoid cutting a jagged line. Cut slowly, checking regularly that you're cutting straight. 

How to cut round trees and shrubs

It's very easy to accidentally catch the base of trees and shrubs with your grass trimmer, which rips the bark, letting disease into the plant. In the worst cases it's possible to kill a tree if the bark is cut right around the trunk. 

Use your guard to protect the tree by placing it against the trunk and then step backwards, pulling the grass trimmer around the base of the tree. Keep the guard between the trimmer head and the tree. 

Some grass trimmers have a plant guard, which is a wire hoop that projects in front of the grass trimmers. Again, remember to keep this up against the tree or bush, and be aware that if you swipe sideways you will cut into the bark. 

How to cut long grass and weeds

Back in the day, this job would have been done using a scythe, so think of your grass trimmer in much the same way. Swing it from side to side, cutting in one direction only. This will push all the debris in the same direction, making it easier to see where you have cut, and to clear up afterwards. 

If you've a lot of trimming to do, it's easy to put stresses and strains on your body, so avoid this by swinging the grass trimmer only as far as is comfortable. Step forward between each swing to move forward in a straight line. Then turn around and walk back in the opposite direction to complete the next line. 

Remember to feed out plenty of line when you're doing this. The line will break regularly and there is a risk that you will lose the line if you don't feed out more regularly. You will also work more efficiently by using the maximum cutting area. 


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