How to Put a Knife on a Trimmer

With the advent of summer, many owners of household plots are concerned about the issue of how to put a knife on a trimmer. No less relevant are the questions of why and when it is advisable to replace the fishing line on the Lawn Mower with a more durable cutting element. In our article we will try to make out all this and give useful recommendations to summer residents.

Why you need to put a knife on a trimmer

The trimmer with a knife mounted on it is most convenient to use for more comfortable mowing of tall and coarsened grass in the country. The scythe line does not cope in such cases. Thin breaks very quickly. Using a thick 2.3 mm cord or homemade rods with cables causes the vegetation to wind up on the spool. This increases the load on the engine. As a result, the piston group and other moving parts of the unit wear out very quickly.

How to Put a Knife on a Trimmer

If the mowing of the weeds is carried out with an electric trimmer without a knife, only fishing line, even if it is thick with a curly section, the problem cannot be solved. There is always a risk of overheating the motor and damage the flexible shaft. And it’s all about the big torque of the electric motor. The grass wound on the spindle creates strong resistance to the shaft, resembling a speedometer cable, which does not withstand and twists.

In order to protect the equipment from premature wear, manufacturers have provided the ability to install special knives on trimmers. The design and shape of existing cutting elements makes it easy to cope not only with coarsened and overgrown grass, but also successfully deal with young shrubbery.

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What kind of knives to put on electric and benzokosa

Before buying and putting a knife on a Lawn Mower, we will find out what they are and in which cases they are used. Today, manufacturers offer consumers a large number of types of these consumables. In general, all cutting tools designed for mowing grass can be classified:

  • By the type of material from which it is made;
  • In the shape of its cutting blades.

The main material for making trimmer knives can be plastic or metal. The use of such consumables is largely dependent on two parameters:

For safety reasons, manufacturers do not recommend placing steel knives on electric trimmers. Almost all motor-scythes powered by an electric network and a battery are equipped with plastic blades. Depending on the manufacturer, they can be of a single disc-shaped design with several blades or in the form of a special mowing head for the installation of removable plastic blades.

Straight bar at gas trimmer and curved at electric

Video: How to Put a Knife on a Trimmer


To put a metal knife on an electric trimmer does not allow its design features.

  1. The curved rod of the unit reduces the distance from its working part to the legs of the mower. If the blades collide with a stone or other solid object, the braid is thrown to the feet.
  2. The high torque that we mentioned above, in the event of a collision of a metal knife with a solid object, transfers a large load to the flexible shaft of the trimmer and its motor. What causes their premature failure.
  3. The handle of an electric braid most often does not have a restrictive bar acting as a stop. Which does not exclude injury to the legs.
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It is these features that allow the use of exclusively plastic knives on trimmers with electric motors. In a collision with an obstacle, the blades are destroyed, thereby protecting the legs of the mower from possible injuries.

Plastic knives cope well with overgrown and dry grass. They can mow nettles and stalks of burdocks.

The use of metal knives only on gas trimmers is also due to design features.

  1. The direct design of the bar increases the distance to the legs, which ensures complete safety.
  2. Convenient U-shaped and J-shaped handles allow to hold the tool firmly. Lawn Mower’s D-shaped handles are equipped with a limiter resting on the leg of the pigtail, which does not allow the head to be allowed to close when the cutting disc meets a solid obstacle.
  3. The clutch of the gasoline engine allows you to smoothly gain speed to the optimum level. And when the blade collides with a hard surface, it can absorb part of the impact.

Thus, gas trimmers with an installed metal knife are best used in large areas. They will successfully cope not only with tall coarse grass, weeds, burdocks and nettles, but also shrubs, as well as young trees.

The shape of the blade blades placed on the trimmer does not affect the quality of the work performed. Speed ​​does not depend on them either. Triangular, trapezoidal, rectangular shapes are all the marketing ploy of manufacturers.

If you plan to prepare hay, then it is best to put knives with a large number of blades on the brushcutter. Look for discs with eight teeth or discs with four large blades and four additional ones. Two and three blade knives will greatly chop the grass.

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How to put the knife on the trimmer

Putting a knife on the trimmer is not so difficult. The manufacturer supplies his tools with a special pin that allows you to lock the gearbox and a key with which you can unscrew the spool with fishing line. The most important thing to observe when changing the cutting elements is the safety precautions and the assembly sequence of disassembly.

The algorithm for installing the knife on the trimmer is as follows:

  1. Remove the protective cover;
  2. We block the drive. To do this, combine two holes. in the shaft hub and in the gear cup. After combining them, insert the pin into the holes;
  3. We turn off the spool with fishing line or the fastening nut holding the boot (clockwise, if the trimmer has not been used) clockwise from the hub;
  4. Next, install the cutting knife, so that the slots on the hub washer coincide with the recesses in the hole of the cutting disc;
  5. Install the boot;
  6. We twist the fastening nut (counterclockwise) while holding the locking pin;
  7. Tighten it using a pipe wrench;
  8. Return the protective cover to its place.

As you can see, there is nothing complicated. Now you can safely proceed to mow the weeds on the site.