How to remove a knife from a trimmer

How to put the knife on the trimmer

With the arrival of summer, many owners of personal plots are worried about the question of how to put the knife on the trimmer. No less relevant are the questions of why and when it is advisable to replace the line on a lawn mower with a more durable cutting element. In our article we will try to disassemble all this and give useful recommendations to summer residents.

What knives to put on an electric and lawn mower

Before buying and putting a knife on a lawn mower, we will find out what they are and in what cases they are used. Today manufacturers offer the consumer 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;
  • By the shape of its cutting blades.

The main material for the manufacture of trimmer knives can be plastic or metal. The use of such consumables largely depends on two parameters:

  • Lawn mowers type;
  • Mowing areas.

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

remove, knife, trimmer

Straight bar for petrol trimmer and curved for electric

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To put a metal knife on an electric trimmer is not allowed by its design features.

  • The curved bar of the machine reduces the distance from its working part to the mower’s feet. In the event of a collision of the blades with a stone or other solid object, the scythe is thrown to the feet.
  • The high torque we mentioned above, in the event of a metal blade hitting a hard object, transfers a large load to the trimmer flex shaft and its motor. What causes them to fail prematurely.
  • The handle of the electric scythe most often does not have a limiting bar acting as a stop. Which does not exclude injury to the legs.

It is these features that make it possible to use exclusively plastic knives on trimmers with electric motors. When colliding with an obstacle, the blades are destroyed, thereby protecting the mower’s legs from possible injury.

Plastic knives do a good job on overgrown and dry grass. They can mow nettles and burdock stalks.

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

  • Straight bar design increases leg clearance for complete safety.
  • Comfortable U-shaped and J-shaped handles provide a firm grip. D-shaped handles of lawn mowers are equipped with a stopper that rests on the leg of the mower, which does not allow the head to come close to the feet when the cutting disc meets a solid obstacle.
  • The clutch of the gasoline engine allows for smooth acceleration to the optimum level. And when the blade hits a hard surface, it is able to absorb part of the impact.

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

The shape of the disc blades supplied to the trimmer in no way affects 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 on making hay, it is best to use knives with a large number of blades on the mower. Note the discs with eight teeth, or discs with four large blades and four additional blades. Two and three bladed knives will chop the grass hard.

Why you need to put the knife on the trimmer

A trimmer with a knife mounted on it is most convenient to use for more comfortable mowing of tall and coarse grass in the country. The line on the lawn mower in such cases does not cope. Thin tears very quickly. Using 2.3mm thick cord or homemade rods with cables causes the vegetation to wrap around 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.

If the weeds are mowed with an electric trimmer without a knife, only a fishing line, even a thick one with a curly section, will not solve the problem. There is always a risk of overheating the motor and damaging the flexible shaft. And it’s all about the large torque of the electric motor. Grass wrapped around the spindle creates strong resistance to the shaft, which resembles a speedometer cable, which does not withstand and twists.

In order to protect the equipment from premature wear, manufacturers have provided for the possibility of installing special knives on the trimmers. The design and shape of the existing cutting elements allows you to easily cope not only with coarse and overgrown grass, but also successfully deal with young shrub growth.

How to put a knife on the trimmer correctly

Putting the knife on the trimmer is not that difficult. The manufacturer completes its tools with a special pin that allows you to block the gearbox and a wrench with which the spool and fishing line are unscrewed. The most important thing is to observe safety precautions and the sequence of assembly and disassembly when changing cutting elements.

The algorithm for setting the knife to the trimmer is as follows:

  • Remove the protective cover;
  • We block the drive. To do this, it is necessary to align two holes. in the shaft hub and in the gearbox cup. After combining them, insert a pin into the holes;
  • We unscrew the spool with line or the fastening nut holding the boot (if the trimmer has not been used yet) from the hub clockwise;
  • Next, we install the cutting knife, so that the slots on the hub washer coincide with the recesses in the hole of the cutting disc;
  • Install the boot;
  • We tighten the fastening nut (counterclockwise) while holding the locking pin;
  • We tighten it using a tubular wrench;
  • Putting the protective cover back in place.
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As you can see, there is nothing complicated. Now you can safely start mowing weeds on the site.

Step by step process

  • Before removing the knife from the mower, fix it with a sturdy board or log resting on the ground. It is necessary that the knife does not move when it is removed. However, some neglect this safety measure and simply hold the insert with their hand.
  • An L-shaped socket wrench or box tool is taken, ideally suited to size. The use of pliers is not recommended. This fitting tool easily spoils the edges of the bolts.
  • Usually the cutting unit is secured with one large bolt located in the middle. Modern models have several fasteners. As a result, you will have to unscrew them all.
  • Bolts are most often right-handed. Therefore, to unscrew the bolt, turn the key counterclockwise. In order to screw it back, it is done the other way around, that is, tighten the bolt clockwise.
  • It happens that over time, the threaded pair sticks, rusts, and it becomes problematic to unscrew the bolt. In this case, special lubricants are used, called liquid keys.
  • If the removal was successful, and all fasteners are intact, then the bolts, nuts, washers are removed into the box for safety. These connections may have to be reused.

Additional Information. Before removing the knife, you need to remember its position. Most often, knives are placed with a tip counterclockwise, and the rotation of the element occurs in this way. However, this advice does not apply to all models. Therefore, attention should be paid to the position of the element. It is in the same position that you will have to put a new knife or screw the old one after sharpening.

Machine tool

The machine will help you get the job done quickly and without much effort. The main thing in this business is not to achieve too sharp edges. If you sharpen them as thin as a razor, then there is a great risk of chipping and breaking.

Sharpening on the machine

While working, it is important to keep the correct angle and remove the metal from the blades in the same amount. The machine does not eliminate the need to edit the edges with sandpaper.

Matrix Turbo lawn mower blade adapter

Unfortunately, Matrix-direct has ended support for this product. In service centers that are on the list.

Turn the mower over to access the cutting tool;
Fix the knife with a wooden block;
Using the right tool, usually a socket or box wrench, unscrew the knife attachment points;
Remove the knife itself.

After cleaning the knife from adhering grass, dirt, you can proceed specifically to sharpening.

To sharpen a lawn mower knife, you will need a stable base. a table or workbench, on the surface of which you can comfortably position and fix the knife for final sharpening. Balanced option. if you have the ability to secure the knife in a vice.

When doing the work, keep in mind that the working part of the knife is hardened, you should try to make the impact on the blade as small as possible and keep the angle of sharpening of the lawn mower knife.

If the working parts of the knife are not damaged. burrs, notches, then you can limit yourself to straightening the blade. For which you can use an abrasive bar or a diamond-coated file. It is not required to remove a large amount of metal, and you can get by with a “thin” tool.

If the knife blades are damaged, they must be removed before sharpening with a coarse file, on an emery wheel or using an electric tool with an abrasive attachment.

If you are doing the work with a file or abrasive bar, then sharpening is done from the center of the knife to the edge. The movement of the instrument is “away from oneself”. After completing the work, it is necessary to check whether the balancing of the lawn mower blade has changed.

The sharpened knife can be installed on the mower and start mowing the lawn.

DIY lawn mower blade adapter


A balance check is performed before installing the knife on the garden equipment. It aims to find out whether the blades of a knife have the same weight. To do this, a sharp strip is put on a pencil with a central hole. The shoulders should be balanced and equal in weight. If one of the sides pulls down, then grind it down a little again.


An independent process for partial disassembly of the vegetation shearing unit begins with preparatory work. It is necessary to observe safety measures and work with gloves. It is necessary to prepare a key in order to unscrew the mount, as well as a small board that will help fix the knife. The electrical appliance is disconnected from the network. At gasoline, the fuel is drained and the spark plug is turned off to exclude the possibility of a sudden contact. Regardless of the type of machine, the owner must unscrew the grass catcher.

Important! Before turning the mower on its side or upside down, inspect it to ensure that there is no gasoline or oil leakage. It is best to drain the oil in the crankcase as well. Otherwise, if a leak occurs, it will be problematic to start the unit.

You can also not turn the mower, but simply place it on a frame or two chairs that simulate a lift. After that, the person approaches the device from below.

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Preparing to remove the knife

The mower can be equipped with:

  • A single two-bladed knife of different shapes;
  • Two knives;
  • Blades with four blades;
  • Composite cutting structure.

In the first case, one knife is used in the form of a small strip. Its length will be the same as that indicated in the characteristics of the device under the heading width of cut. Usually it is 30-50 cm.

In the second case, two knives are used, which are attached at an angle of 180 degrees relative to each other.

On a note! Another option for the cutting system is the four-blade blades. They are connected to each other by a common base or not.

In the latter case, we are talking about several knives located at different heights. Such a nozzle in the form of an upper blade is equipped with modern models that have an additional function of mulching the lawn. Plants from the grass tank fall onto the upper blades. Sharp edges carefully crumble the greenery, which after the procedure covers the ground of the lawn and turns into mulch.

How to remove a knife from a lawn mower

Cleaning the knife before sharpening

Before sharpening the knife, clean it thoroughly. Plant sap and small particles of grass accumulate on the steel strips. In this case, the juice hardens over time and turns into a tough crust. It is not worth washing the blades, it is best to pick up a sharp metal scraper in the garage or use a brush.

It is not necessary to polish the cutting element of the machine to a shine, the main thing is to remove the adhering waste. After that, you need to improve the knife by straightening it and removing all the irregularities. Bumps arise from solid debris and stones hitting the blades. The correct option in this case is to work with a hammer. With the help of this tool and a flat working surface on which the knife is placed, all local distortions can be corrected.

Cleaning the knife before sharpening

Experts advise to start leveling the blade from the edge, gradually moving towards the middle part. As a result, the steel strip should become as flat as possible. Only in this case will it be able to fulfill its function, creating an air flow that transports the grass to the tank for collecting plant residues.

Popular manufacturers

Both lawn mowers and accessories for them, for example, knives, are produced by popular manufacturers, the best of which are the following:

  • Bosch;
  • Gardena;
  • Craftsman;
  • Champion;
  • Makita;
  • Hyundai;
  • Daewoo;
  • Honda;
  • “Bison”;
  • Interskol;
  • “Anchor”.

The mower does not cut the grass

There are two options here.

  • The knife is blunt or broken. Sharpen it with a file, an angle grinder, on a grinder (you need a flat-cylindrical sharpening stone) or on a machine (or drill) with emery wheels. Check torch balance.
  • The cutter itself is not set correctly. Set a gap in the cylindrical mower between the rotating cylinder and the blades of the knife equal to the thickness of the sheet of paper.

Varieties and sizes

Too large a knife will “plant” the engine speed, which will lead to more wear on the latter.

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Finally, the material of the cutter is critical in terms of safety. Most knives are made of stainless steel, but there are also plastic knives. The fact is that when the cutter hits a large stone, the fragments of steel can hurt you with a ricochet. A blow from a plastic debris is much more harmless. unless it hits the eye. The plastic knife is the choice of owners of mowers with a curved flexible shaft. The utility knife for lawn mowers not only cuts grass and bushes, but also crumbles them. due to the larger number of blades (up to 8). Finely chopped grass will do as a top dressing (mulch) for the lawn.

Echo Hedge Trimmer Blade Replacement #X411000271

Lawn mower knives: requirements, varieties, mounting features and selection

  • Purpose and requirements
  • Varieties and sizes
  • Blade and adapter shapes
  • What should be the sharpening angle?
  • How to fix and replace?
  • Popular manufacturers
  • Selection Tips
  • Common breakdowns
  • The mower does not cut the grass
  • The rotor with the knife does not spin in the mower

A knife is no less popular than a fishing line or cord, a working tool for a lawn mower. If in the trimmer you can do with fishing line or cord, then the knife is basically a cutter for lawn mowers, the power of which is noticeably more than that of trimmers.

Common breakdowns

Most often, the malfunctions are as follows: the mower does not cut the grass or does not turn on at all.

How to fix and replace?

The knife should be changed every quarter or during the growing season, although sometimes it should be changed sooner. Installing the knife is as follows:

  • if the mower is in operation, suspend it; for electric braids, it is enough to turn off the power (cord from the outlet, disconnect the battery); lawn mowers are disconnected from the key, unused fuel is drained back into the canister;
  • turn the mower to one side and remove the grass catcher;
  • clean off the ground and grass adhering to the working parts from the knife and the protective visor;
  • remove the visor (protective cover) of the knife; it holds back the grass scattered in all directions (when mowing);
  • unscrew the mounting bolt using a wrench or a head, the knife should not turn, it itself is attached to the adapter; it is recommended to wear work gloves before removing the knife so as not to cut yourself;
  • insert a new (preferably exactly the same) knife and tighten the bolt tighter, when it is loosened, the machine vibrates, or the blade itself may fly off.
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If vibrations appear, but there is no replacement knife, it is necessary to balance the old one. Remove the knife and check its balance by hanging it on a screwdriver or nail with a large head. For this, the working part of the screwdriver is threaded through the central hole of the cutter itself. If there is an imbalance. one particular point will tilt, in this case, grind off a little metal. With repeated sharpening, the mass of the point that outweighs the others will decrease, and the center of mass will shift to its place. After balancing is complete, reattach the adapter and tighten the modified torch. If the adapter has a key holding it on the motor (gearbox) shaft. do not forget to press it into place.

If you find a previously purchased replacement cutter, install it immediately. In some cases, the holder also wears out. it needs to be replaced.

What should be the sharpening angle?

Lawn mower cutters are always sharpened at a 30-degree angle. A smaller angle will make the blade too thin, like a razor rapier. it will quickly serrate, bend, it can only mow short grass. Weeds and bushes are guaranteed to “ruffle” the edge. Too large an angle will lead to the knife hitting and breaking bushes more, tearing off the stalks of grass. rather than cutting off both. In addition, the point should be sharpened on one side. and only slightly, barely noticeably sharpened from the opposite.

Purpose and requirements

The purpose of the mower cutter is to cut the grass evenly and neatly in large quantities. In one session, when mowing one hundred square meters of a plot, you can collect tens of kilograms of grass. If the lawn mower has the function of shredding (mulching), such a knife should also chop the grass. The mower’s cutter is designed so that its blades create upward thrust for the grass that has just been cut. She carries this herb into the collector.

The best alloy for a mowing knife is stainless steel. over, it must have a hardness of at least 55 units on the Rockwell scale. A lower hardness value will quickly dull the cutter. especially when cutting weeds and trimming bushes. Since the cut grass contains not only moisture, but also other active components, ordinary steel would quickly become covered with a brown coating after the very first mowing session. Stainless steel, creating on its surface a chromium oxide that resists corrosion (chromium is also included in the list of alloying additives), does not allow the knife to rust.

Important! In addition to being tough, the cutter must also be sturdy. If, during work, he stumbles upon a stone, then it should not fly apart.

Why does the line unwind on the trimmer?

How to put the knife on the trimmer (lawn mower)?

The algorithm for setting the knife to the trimmer is quite simple. The procedure is almost identical to the procedure for replacing the trimmer coil. So let’s get started:

Important! Make sure the trimmer is disconnected from the power supply during the preparatory phase. Unplug the electrical model. As for the lawn mowers, the engine switched off is enough to continue the procedure.

Remove the protective cover.

If a spool is installed, remove it. How to remove the coil read in our material with a photo.

Install the knife by centering the slots on the hub washer with the notches in the hole in the disc.

Install the thrust washer and mounting cup

Tighten the nut with a pipe wrench counterclockwise while holding the locking pin.

Blade installed. trimmer ready to work.

How to wind the line onto the trimmer spool?

The effective operation of the trimmer without recharging depends on whether the fishing line is correctly wound. For winding, you will need to do the following:

Fold the line in half so that the difference in length between the remaining ends is 10-15 centimeters.

Insert the formed loop into the groove of the coil.

In line with the indicated direction on the spool, carefully lay the line.

Fix the short end in the groove on the side and the long end in the opposite.

Place the inner spool with wound tape into the spool body. Pull the line out of the locking grooves and put on the cover.

If necessary, trim the ends of the line to 10-15 centimeters.

The line is wound, it remains only to install the spool on the trimmer.

You can familiarize yourself with the detailed instructions with the photo by following the link to the article. to How to properly wind the line around the trimmer spool.

How to remove the spool from the trimmer?

Frequently asked questions: Trimmers

Why does the line break on the trimmer?

How to install the bobbin on the trimmer?

The process is quite simple and its algorithm can be easily adapted to the trimmer of any manufacturer.

So let’s get started:

  • Align the hole in the washer with the hole in the gear cup
  • Secure the parts with a special locking rod
  • Carefully unscrew the retaining nut from the hub. In FUBAG models, this operation is performed clockwise. As for analogs, try not to rip the thread at this stage, correctly determining its direction.
  • Remove the cup from the shaft and the washer. There is one important nuance here: the flange washer must remain in place.
  • Twist the bobbin fully counterclockwise.