How to put a cover on the grass trimmer

How to install the blade on the grass trimmer

With the advent of summer, many owners of homestead plots are concerned about how to put a knife on the grass trimmer. Equally relevant are the questions of why and when it is advisable to replace the line for the trimmer on the brushcutter with a more durable cutting element. In our article we will try to break it all down and give useful recommendations for gardeners.

A grass trimmer with a blade mounted on it is best for cutting tall and coarse grass in the countryside more comfortably. The line for the trimmer on the brushcutter fails in such cases. Thin grass tears very quickly. Using a thick 2.3 mm of cord or homemade rope ropes causes vegetation to wind up on the bobbin. This increases strain on the engine. As a result, the piston group and other moving parts of the machine wear out very quickly.

If you mow your weeds with an electric trimmer without a blade, you can’t solve the problem with just one line, even if it’s thick with a curly section. There is always a risk of overheating the electric motor and damaging the flexible shaft. And the thing is in the high torque of the electric motor. Grass wrapped around the spindle creates a strong resistance to the shaft, reminiscent of a speedometer cable, which can not withstand and twist.

In order to save the technique from premature wear, manufacturers have provided the opportunity to install special knives on trimmers for grass. The design and shape of the existing cutting elements makes it easy to not only cut through rough and overgrown grass, but also to successfully cut through young growth.

How to change the disk on a trimmer and for which brushcutters they are used

Grass trimmers differ in the way the motor works. Distinguished between electric and gasoline versions. The second. have the power is much more than their competitors.

For miniature trimmers, plastic knives or lightweight metal elements are traditionally used. Even pobedite discs for grass trimmers can be used for higher capacity mowers. But it’s not just the power of the devices that is limited.

The second principle is the mechanism: rigid or transmission. In the first one, rotation is transmitted on the basis of a shaft, and in the second one. by a steel cable. Flexible wire does not work with large discs, as it quickly becomes unusable. Therefore, for a flexible gear, use a spool of fishing line instead of the knives. Find out the type of device even before you buy it, so that you don’t end up with a quick breakdown.

Plastic circles on the grass trimmer. when to use

If metal milling and paddle discs are used on gasoline trimmers, then it is recommended to use plastic circles for electric tools. Their main advantage is their low weight, so the load on the electric motor is completely eliminated. Structurally, the nozzle is a plastic base on which the knives are attached along the perimeter. Blades are made of soft plastic, which bends without deforming when in contact with an obstacle. The blades are mounted on a circular base at a 120 degree angle.

They are designed for mowing dense grass with electric trimmers, when the line for the trimmer fails. If the nozzle has a high moment of inertia, it can be reduced by making symmetrical holes. When the tines are blunted, they need to be sharpened at a 30 degree angle using a low to medium roughness grinding wheel.

disc design Applications Characteristics
Cutter peorized with 40 teeth Gentle cutting of lawn and tall grass. Great for cutting in fields and brushwood Eliminates winding of the grass on the disc and low stress on the gearbox. High performance in large quantities of grass
router bits with more than 40 teeth (60-80) For small trees with 7-8 cm thick stems Suitable for mowing grass with small growing trees
Solid with the number of teeth from 8 to 32 For cutting thin and stiff raspberry and currant bushes. Effective at mowing grass, but only with powerful equipment Cut small bushes and shrubs efficiently. The gearbox is stressed
One, two, and three blade blades Stiff grass, brushwood They break the grass several times, chopping it, which increases the load on the gearbox
Blade with 4 or more knives Branches and hard grass cutter, can be used for making hay Has a low moment of inertia
Plastic blades For small and dense grass in backyards Does not stress the electric motors of trimmers


Some manufacturers of trimmers with rigid construction of the transmission shaft additionally complete their tools not only with lines, but also with steel discs. This is not always the case, and if such a situation is appropriate, a metal disc is installed instead of the mowing head with a fishing line, if necessary.

What blades to put on the electric and lawnmower

Before you buy a brushcutter knife, let’s find out what they are and when they are used. Today, manufacturers offer the consumer a large number of types of these consumables. In general, all cutting tools for mowing the grass can be classified:

Main material for trimmer blades can be plastic or metal. The use of such expendable elements largely depends on two parameters:

For safety reasons, manufacturers do not recommend putting steel blades on electric grass trimmers. Almost all electric and battery-powered brushcutters are equipped with plastic blades. Depending on the manufacturer, they can be of solid disc shape, with several blades, or in the form of a special mowing head that provides for installation of removable plastic blades.

Gasoline grass trimmer has a straight shaft and electric trimmer has a curved shaft

Put a metal blade on the electric trimmer for grass does not allow its design features.

  • The machine’s curved boom reduces the distance from its working part to the mower’s legs. When the blades hit a rock or other hard object, the electric grasshopper is thrown back against the legs.
  • The high torque we mentioned above, in the case of a collision between a metal blade and a solid object, transmits a large load on the flexible shaft of the grass trimmer and its motor. Which causes them to fail prematurely.
  • The handle of the electric mower most often does not have a stop bar. Which doesn’t rule out foot injuries.


It is these features that make it possible to use exclusively plastic blades on trimmers with electric motors. When hitting an obstacle the blades break thus protecting the mower’s legs from possible injury.

Plastic blades handle overgrown and dry grass well. they can mow nettles and burdock stalks.

The use of metal blades only on gasoline trimmers is also due to design features.

  • Straight boom design increases distance to the legs, which provides complete safety to the operator.
  • Comfortable U-shaped and J-shaped handles let you hold the tool firmly. D-handles of the brushcutter are equipped with a stopper that rests against the mower’s leg to keep the head away from the legs when the cutting disc hits a hard obstacle.
  • Gasoline engine clutch provides smooth, positive RPM acceleration to optimum performance. And when the blade hits a hard surface, it can absorb some of the impact.

Thus, gasoline grass trimmers with metal blade installed are best used on large areas. They can successfully cope not only with high rough grass, weeds, burdocks and nettles, but also bushes and young trees.

cover, grass, trimmer

The shape of the blades of the disc supplied to the grass trimmer does not affect the quality of work performed. And that does not affect speed. Triangular, trapezoidal, rectangular shapes are all a marketing ploy by manufacturers.

If you’re planning to make hay, it’s best to use a brushcutter with more blades. Look for discs with eight teeth or discs with four big blades and four extra ones. Two- and three-blade blades will shred grass severely.

cover, grass, trimmer

The gasoline grass trimmer design

All the machine parts are mounted on a long metal bar. On its upper end is the gas tank, the combustion engine and the starter for starting. At the lower end, there is a spindle that turns counterclockwise.

A spool of fishing line or sharp knives (disk with teeth) of steel or plastic is mounted on it. Inside the rod, which is a hollow tube, there is a rigid or flexible shaft that transmits the rotation from the engine to the working tool.

Side note! If the boom is straight, it uses a rigid shaft that connects to the gearbox above the spindle and transmits torque from the drive. If the boom is curved, there is no gearbox, and the shaft is used flexible.

cover, grass, trimmer

In the middle of the shaft is a handlebar support, which can be D-shaped or bifurcated to look like a bicycle handlebar. Asymmetrical folding handles (as Husqarna brushcutters) are very handy. Buttons and levers for controlling the trimmer are on the handlebar or shaft.

The motor, control elements and spool/disc are connected by a flexible cord. The boom comes in one piece, collapsible and telescopic. The length of the last two types can be changed to adjust to the height of the individual. Some models have fasteners for lap belts. Disc or spool (bobbin) is covered with a screen to protect the person cutting the grass.

Cutting tool is a spool with a trimmer line (cord, string) with a diameter of 2-3 mm wound inside. In some models, the line for the trimmer is wound with a reserve, and when lightly hitting a hard surface, it is automatically pulled out of the bobbin. Other trimmers have a piece of cord inserted in the spool and the excess length is cut off against the sharp edge of the shroud.

How to replace string trimmer edger line

In addition to lines, some brushcutters are equipped as standard with a disk with sharp serrated edges. The teeth can be shaped in different ways. For cutting down branches and bushes, use a knife nozzle or a cutter similar to a circular saw disc.

For your information! Some trimmer models can be supplemented with other attachments: a brush, a chain saw, a cultivator for the soil.

cover, grass, trimmer

Preparing the correct fuel mixture

Before you start running in a new lawn mower engine, you also have to correctly prepare the fuel mix. As is known for two-stroke engines, it is prepared from special two-stroke oil and gasoline taken in certain ratios. You can find out the proportions from the manual supplied with the tool or on the label of the lubricant. Check the manual for the recommended type of fuel and recommended type of engine oil.

Prepare only enough fuel for one pass of grass. Use special plastic canisters for fuel or separate glass or metal containers. It is best to use a medical syringe to fill the oil.

When getting ready to test drive a new lawnmower, many are faced with the problem of preparing the fuel mixture. And the reason for that is the discrepancy in the tool manufacturer’s instructions and in the engine oil manufacturer’s instructions. The first recommends a ratio of 1:25.

According to the experts’ opinion, if the manufacturers’ instructions to the brushcutter manufacturer write the proportion 1:25 or 1:30, it most probably is either a cheap tool with a bad coolant, or the manufacturer doesn’t know what kind of oil the consumer will add. But here it should be understood that an excess of lubricant does not affect the performance of the grass trimmer in the best way. Excess oil does not burn out completely when the engine is running. It corks and clogs the cylinder and piston.

What to do in this situation when running in a new tool? The ideal solution is to buy the oil that the mower manufacturer recommends. In the case of running-in engines, when you can’t buy the recommended oil, it’s best to buy a good Husqvarna two-stroke oil for the same name gasoline tools. It is not cheap, but it lasts a long time. You have to mix it as it is written in the instruction on the jar.

Remember, it is best to use the oil manufacturer’s recommended oil ratio. It is better to find out by experiment if the recommended oil ratio is correct. If with the proportion recommended by the manufacturer of the grass trimmer the engine is snotting oil and you can see leaks on it, then the proportion must be increased.

The procedure for installing the disc on the grass trimmer

Installing the blade on the grass trimmer is very easy. This is done with the wrench that disconnects the cutting head and the pin that locks the gearbox. The procedure is as follows.

  • First of all, you should unplug the electric grass trimmer, gasoline trimmer. just shut off. Detach and set aside the protective shroud.
  • Next, align the holes on the gearbox and the shaft in order to insert the pin and lock the drive.
  • If a bobbin with a fishing line was used, it must be unscrewed in a clockwise direction.
  • Then you need to find a nut to tighten the blade.
  • The next step is to install the knives. Owners of trimmers often wonder which side to put the disc. Do it in such a way that the marking with numbers and letters is on top.
  • Then you need to put the dust cover on top, and above it. a fixing nut, which must be tightened tightly with a wrench.
  • The last step is to install a protective cover.

As you can see, the procedure is very simple and the same for many brands, whether it is STIHL or Husqvarna.

For your information! If the owner of the device wishes to replace the disc back to the line for the trimmer, you can install the spool with it in a similar way.

Sharpening a disc

No matter how good or bad the blade may be, it becomes blunt and does not cut the grass properly over time. If the blades are still relatively new, and replacement is not feasible, you can sharpen them with your own hands.

Important! Only discs without hardfacing are suitable for sharpening. discs are to be discarded and new ones purchased instead.

  • Disassemble the grass trimmer, remove the blades;
  • Carefully check the disc. if you find any cracks, it is better to replace the part for a new one, because its further use is not safe;
  • bent blades can be carefully bent with a hammer;
  • Given the size of the disk, you need to choose the right file for metal, this will ensure a more comfortable work;
  • at an angle of 30° all upper cutting edges of the discs are sharpened equally;
  • Reassemble the grass trimmer in reverse order.

To sharpen the disc you can use an emery machine on a low rpm setting a medium grit emery wheel. With such a tool the process will move much faster. To be safe, you need to wear gloves on your hands and a face mask or goggles.

For example, gasoline and electric grass trimmers use plastic and metal blades of different shapes and a different assortment of blades. They are selected according to the type of work to be performed and the size of the area to be processed. If the blades of the mower become blunt it is easy to sharpen them or change them yourself. Despite the simplicity of the procedure, you need to be careful and remember about safety, so as not to injure yourself due to carelessness or not to damage the technique. For a more detailed description of blade replacement for a particular model of grass trimmer, please refer to the instruction manual or the manufacturer’s official website. For clarity, the general scheme of the process is shown in the video.