Strimmers are a key part of any garden or groundcare tool collection to help you prepare a lawn for mowing, or to trim grass and vegetation along borders, pathways, or less accessible areas. Strimmers are versatile, and relatively easy for anyone to use. But how do they actually work?
In this guide, we’ll take you through exactly how strimmers work, along with some useful tips on how to use them safely. Keep reading to learn more from the team at Hughie Willett Machinery…
Parts of a strimmer
Firstly, to understand how a strimmer works, you need to know about the different parts. In this section, we’ll explain the main elements included in the business end of a strimmer - the strimmer head.
For more information about strimmer terminology, check out our Ultimate Strimmer Buying Guide.
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Top casing: The top casing, also known as the top cap, of the strimmer head is the end which faces the ground. This is where you’ll find the bumper to release more cutting wire on a line strimmer.
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Cutting wire: The cutting wire provides the functionality of a line strimmer. This is typically wound around a spool within the head unit, or it can be inserted as separate pieces.
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Wire eyelet: The cutting wire is threaded through the wire eyelets for guidance - and to ensure the wire remains in place.
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Outer housing: The outer housing makes up the body of the strimmer head. This contains the internal mechanisms, the spool, and is where the head attaches to the strimmer shaft.
Note - this diagram is for a wire strimmer. Bladed strimmers have different head fittings as they need to allow room for the blade to rotate fully.
How does a strimmer work?
Now that you have a better understanding of the different parts of a strimmer head, it’s time to focus on the mechanics and how they fit together to power your tool.
Or, in simpler terms, how does a strimmer work?
In a strimmer, the power source connects to the head through the shaft. This could be from a 2-stroke petrol engine, a mains electric supply, or a Li-ion battery.
The engine is connected to a clutch, which in turn is connected to a drive shaft. When the throttle trigger is pressed, this engages the clutch and allows the drive shaft to start moving.
The drive shaft powers the strimmer head, making it spin. In line strimmers, this spinning forces tension through the wires, causing them to stiffen and providing your cutting power. The process is largely the same for blade strimmers, where the rotation of the drive shaft causes the blades to move.
The speed and thickness of your cutting wire will dictate the types of material you can cut through. Most domestic line strimmers use a nylon or plastic wire, and are able to cut through grass easily. For stubborn weeds and vegetation, using a thicker wire will give you more power to tear through the stems.
Domestic blade strimmers are usually plastic, which has the necessary cutting power for most applications and are less dangerous for the average person to use. Groundcare professionals may prefer a more powerful strimmer with metal blades to tackle thicker plant growth on a regular basis.
Note - your level of experience tends to dictate the type of engine you should choose. Petrol strimmers require more skill to start, as you usually need to use a starter rope to get the engine running. Electric strimmers are simpler for beginners to use, as you just need to press a button.
How to replace strimmer wire
As you have seen, line strimmers use a length of nylon wire to cut through grass. This wire is typically wound around a spool within the casing of the strimmer head, which is gradually released over time as it wears out or breaks.
Modern strimmers tend to have a bumper on the bottom of the strimmer head that can be pressed on the ground to release more wire, or have an auto-feed system. If too much wire is released, a blade on the inside of the strimmer guard will cut the wire to size as it rotates.
For most domestic users, a line strimmer is perfectly sufficient to cut long grass and neaten hard to reach areas around the garden. However, the main disadvantage to a line strimmer is that you’ll need to replace the wire when it runs out.
Fortunately, the process to replace strimmer wire is relatively straight-forward and easy for anyone to do. Below we’ve laid out step-by-step instructions for how to replace your strimmer wire.
Note - these instructions are for a dual line strimmer.
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Make sure your strimmer is turned off before you touch the base to prevent injury.
Top tip - disconnect the spark plug on a petrol strimmer to ensure it doesn’t accidentally start while you’re replacing the head.
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Remove the head housing from the main body. Depending on the model of strimmer, you may need to press tabs down, or unscrew the casing.
Top tip - take care to avoid the blade on the guard when you’re removing the strimmer head.
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Lift out the wire spool from the housing, and remove any remaining wire.
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Fold your new trimmer line roughly in the middle, making sure one end is approximately five inches longer than the other.
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Insert the fold of the wire into the slit in the centre border of the spool, then wrap the wire around, making sure to maintain line tension throughout. Wrap the line evenly on both sides.
Top tip - make sure the spool is oriented the right way otherwise your wire will not rotate or release properly. There should be an arrow on the spool to show you the right direction to wrap the wire.
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Place the shorter length of wire into one of the notches in the top of the spool, leaving approximately six inches of line out.
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Continue wrapping the remaining wire until you reach the opposite notch, then slide the longer end into place. You should have a similar length of around six inches remaining.
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Insert the spool back into the strimmer head housing.
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Holding the spool in place, release the wire from the notches and place them into the wire eyelets.
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Align the eyelet shafts, and replace the strimmer housing back onto the head.
For single line strimmers, once removed you’ll need to insert one end of the wire into the spool. From there, you should wrap the line neatly around the spool for an improved feed. To reinsert the spool, slip the extra wire length through a hole in the strimmer housing, then push the spool into place and replace the cap.
Some strimmers use individual lengths of wire. When these need replacing, you simply need to load the strips into the head assembly through the wire eyelets until they’re snug.
An alternative option is to replace the strimmer head entirely. This can be done by unscrewing the old head and rescrewing the new one into place - making sure you’ve oriented it the right way.
Keep in mind that whilst replacing the head can be easier, it creates more material waste.
Why does my strimmer line keep breaking?
Line strimmers are incredibly useful in domestic settings because they’re safer than blade strimmers but can still get the job done. However, the main issue is if the line breaks midway through the job. When this happens, it can be frustrating - but what could cause a strimmer line to break?
Below we’ve compiled a selection of the top causes of strimmer line breakage, along with some useful tips and tricks to avoid this.
Contact with an obstacle
One of the most common reasons your line can break is if it comes into contact with an obstacle. Whilst the nylon line is strong enough to cut through grass and weeds, denser objects like stone and wooden fencing can cause the line to snap.
Top tip - spend five minutes clearing the area of rocks and other garden detritus to reduce the chances of your line snapping on an obstacle.
Poor quality strimmer line
Using poor quality wire can result in more frequent breakages because the line isn’t up to the tasks you’re putting it through.
Make sure to check what your wire is made from. Nylon is fairly strong, but this can be weakened in cheaper wire where the nylon is mixed with other materials. You should also check the shape, as round wire is the strongest in a strimmer.
Top tip - make sure you buy from reputable brands and suppliers, like Hughie Willett Machinery.
Incorrect strimmer line
Using the right wire for the make and model of your strimmer is essential. Incompatible wire can cause blockages, break prematurely, not feed through the system properly, or even cause damage within the strimmer head.
Before buying a new reel, make sure the wire is the right shape, length and thickness to match your strimmer.
Top tip - always make sure to check manufacturing guidance if you’re unsure what size and type of strimmer wire you need for your tool.
The job is too big
Strimmers are a wonderful groundcare tool, but you must be careful not to use them for jobs they’re not suited for. Line strimmers are designed to cut grass in short bursts, either in more inaccessible areas or to prepare a lawn for mowing. Using them to mow a large area, or trying to cut through thicker vegetation can cause the line to snap more frequently.
Additionally, using a thin wire on a bigger job will cause the wire to break, as it doesn’t have the power to complete the task.
Top tip - make sure you’re using your strimmer for the intended purpose. For larger groundcare applications, why not check out our great range of lawnmowers?
Wear and tear
Wear and tear is a natural part of any tool's lifespan, as repetitive use causes parts to age and wear away under the strain.
Your strimmer line may be breaking because it’s simply gotten too old to work efficiently. As nylon ages, it can become brittle and lose flexibility, which causes it to break more often during use.
Top tip - check your strimmer wire regularly, and replace it if you haven’t used your strimmer for a long time.
Blockages
Your strimmer line may not be working efficiently and breaking more often if there is dirt or debris clogging the mechanism. Clumps of grass or soil can build up, causing your line to break or get damaged during use.
Top tip - clean your strimmer head regularly to prevent dirt and grass from building up and causing blockages.
How to use a strimmer
As we’ve mentioned previously, strimmers are designed to cut grass and plant materials along the edges of a lawn or in areas where a mower would struggle to work properly. They have a fairly simple design to do this, meaning it’s easy for anyone to use a strimmer.
In most cases, you should hold the strimmer level over the grass to allow the wire or blade to cut as evenly as possible. Using a gentle sideways motion, allow the strimmer to cut through the grass in a controlled manner. You might want to consider using a harness to help you hold your strimmer safely.
Moving from left to right, or right to left, utilises the edges of the wire or blade. This is where the majority of the cutting power comes from, so it’s more effective than holding the strimmer head in place.
Top tip - make sure to hold your strimmer in two hands for maximum safety and control.
We’ve also put together some of our top tips for how to use a strimmer safely and accurately depending on the job you’re doing.
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Check the cutting direction of your strimmer. If your strimmer rotates clockwise, grass will be ejected from the right side with the better cutting edge on the left. Knowing this will help you position yourself and the tool for maximum efficiency.
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When you’re edging a border of a lawn, hold the strimmer flat at the desired (but comfortable) level and walk along the path to create neat, straight lines.
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To taper around an obstacle, hold your strimmer at a slight angle to cut the grass at an incline - then blend with the rest of the lawn for a more attractive finish.
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When scything longer weeds, hold the strimmer securely in a secure stance and move the tool in a shallow U-shape around you.
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Screeding weeds describes the method of cutting through weeds in cracks, or between paving slabs. To do this, angle the wire until it’s just skimming the ground and swing into the weed base. This takes plenty of skill and practice, as your wire will snap if done wrong.
Can you use a strimmer on wet grass?
Technically, whilst you can use a strimmer on wet grass, we wouldn’t recommend it for a variety of reasons.
For starters, water can make even level terrain slippery, which increases your chance of injury. You definitely shouldn’t trim grassy slopes in wet weather, as this can be dangerous for everyone involved.
You could also damage your strimmer if you use it on wet grass, or in wet weather. Electric and cordless strimmers shouldn’t be exposed to water, as this can cause issues with the battery.
If you have a line strimmer, cutting wet grass is much harder than when it’s dry. The weight of the water can lead to an uneven finish, so you’d need to go over areas again, which is a waste of time. Plus, wet grass is sticky and difficult to clean off, and has a tendency to clump, which could create blockages around the strimmer head.
Cutting wet grass could even lead to an increased chance of lawn diseases. Fungal spores and bacteria thrive in mild, wet conditions, which could create a breeding ground to infect your grass and damage your lawn.
Overall, we recommend waiting for your lawn to dry before using your strimmer. The best time for grass trimming is around midmorning, when the dew has dried but it isn’t too hot in the day for you to work comfortably.
Where’s the best place to buy a strimmer?
At Hughie Willett Machinery, we’re proud to be one of the UKs leading groundcare machinery and tools suppliers.
Our team of experts are always on hand to provide you with the best advice and information across our wide range of products. Get in contact with us today to make buying your next strimmer and accessories even easier.
Shop strimmers at Hughie Willett Machinery today
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