How to Change a Disc on a Trimmer

If the disc on the trimmer is used regularly, it needs to be removed from time to time and sharpened or replaced with a new one. This part can be made of metal or plastic, have a different number of blades, but the replacement process remains the same. Moreover, this procedure is similar for technology from different manufacturers, whether it be Carver or Huter, but slight differences are possible. Changing the knife on the trimmer is quite simple if you follow the safety precautions and know the correct procedure, the description of which can be found in the user manual. The entire replacement process step by step, as well as the method of self-sharpening knives, will be described in this material.

When the use of knives is relevant

When using lawn mowers in suburban areas, the most popular nozzle is fishing line. It has a low price, suitable for different trimmer heads, safe to use. The disadvantage of using fishing line is that it is convenient only for mowing low growth. In other situations, the string immediately becomes clogged, regardless of whether a gasoline or electric trimmer model is used. In addition, vegetation is wound on the spindle, which creates significant resistance on the shaft and leads to its breakdown. It can also provoke a failure of the piston system in lawn mowers or a burnout of the motor in trimmers.

How to Change a Disc on a Trimmer

Therefore, for mowing tall or hard vegetation, various nozzles are used. So, for harvesting tall and rough grass, thin shoots of trees and shrubs, it is better to install and use a disk. This nozzle clogs much less often, which contributes to greater wear resistance of the equipment.

Features of lawn mowing discs

Knife disks are produced in plastic and metal, as well as in various shapes to perform diverse tasks.

  1. Two-, three- and four-blade Knives with pronounced blades are used for mowing grass and overgrown trees. However, they are not suitable for harvesting hay, as they chop the shoots by chopping them several times.
  2. Massive four-bladed discs are intended not only for clearing the ground from grass, but also for mowing hay. They prevent multiple cutting of the shoots, thereby making them suitable for harvesting for the winter.
  3. Perimeter Cutting Blades relevant for bevel reeds and reeds. Such knives are very heavy – this is a necessary quality to cut through thick stems.
  4. Professional saw tooth discs for brush cutters and lawn mowing, small trees and bushes can be cut.

As an alternative to metal discs, plastic knives are used. They do not need to be tightly mounted in the head, but they rotate as a result of centrifugal force. The durability of plastic knives is high, so the service life is quite long.

Order of installation of a disk on the trimmer

Installing the knife on the trimmer is very simple. To do this, use the complete key that disconnects the cutting nozzle and the pin blocking the gearbox. The procedure is as follows.

  1. First of all, you should disconnect the electric trimmer from the network, gasoline – just drown. Detach and remove to one side the protective cover.
  2. Next, you need to combine the holes on the gearbox and shaft to insert a pin into them and lock the drive.
  3. If a spool with fishing line was used, it must be unscrewed clockwise.
  4. Then you need to find a nut to tighten the knife.
  5. The next step is to install the knives. Trimmers often wonder which side to put the disc on. This should be done so that the markings with numbers and letters are on top.
  6. Then you need to put the boot on top, and above it – the fixing nut, which must be tightly tightened with a wrench.
  7. The last step is to install the protective cover.

As you can see, the procedure is very simple and the same for many brands, whether it is the equipment of the company "Stihl" or Husqvarna.

Disc Selection Criteria

You need to choose a plastic or metal knife, considering the area of ​​the plot to be processed, as well as the type of trimmer – electric or gasoline. The number of blades will depend on which shoots you need to remove with the tool. You can select the desired shape of the disk, the number of blades and the material of manufacture using the instruction manual of the device. Usually it prescribes which cutters it is recommended to use to solve certain problems.


It is not recommended to put metal knives on electric braids, since the design features make their use dangerous for the user. This is due to the curved shape of the rod, the lack of stops on the handles, as well as the high speed of rotation.

Flexible Trimmers in terms of safety, plastic knives should be used. Their purpose is mowing soft grass, dead wood. While metal discs do an excellent job with tall, dense, hard shoots, shrubs, and also shoots of trees.


The number of blades is important in solving diverse problems. So, for chopping grass, two or three pieces are enough. For haymaking, it is necessary that the disk had from four to eight blades. To destroy small shoots of trees and shrubs, instead of lobes, there should be a large number of small teeth on the disks.

Disc sharpening

Regardless of the quality of the disc, over time it becomes dull and begins to cut grass poorly. If the knives are still relatively new, and replacement is not practical, you can sharpen them with your own hands.

To sharpen disks, you must:

  • Disassemble the trimmer, remove the knives;
  • Carefully inspect the disk – if cracks are detected, it is better to replace the part with a new one, since its further operation is unsafe;
  • Bent blades can be gently bent with a hammer;
  • Given the size of the disk, you need to choose the right file for metal, this will provide more convenient work;
  • At an angle of 30 ° equally sharpen all the upper cutting edges of the disks;
  • Reassemble the trimmer in the reverse order.

For sharpening the disc, you can use the emery machine at low speeds, setting up a grinding wheel with medium grain. Through such a tool, the process will move much faster. For safety, you need to wear gloves on your hands, and a face mask or glasses on your face.

Video: How to Change a Disc on a Trimmer

So, for grass mowing on gasoline and trimmers, plastic and metal discs of various shapes and with a different set of blades are used. They are selected in accordance with the type of work performed and the size of the cultivated area. If the knives on the mower are dull, they are easy to sharpen or change yourself. Despite the simplicity of the procedure, you need to be careful and remember about safety so as not to be injured by negligence or damage the equipment. A more detailed description of the replacement of knives for a specific trimmer model can be found in the operating instructions or on the manufacturer’s official website. For clarity, the general process diagram is shown in the video.

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The trimmer, whether it is gasoline or electric, is the only right solution for mowing grass in hard-to-reach places that cannot be handled by a wheeled lawnmower. As a cutting tool, trimmers use metal knives or a special fishing line, which is tucked into the trimmer coil. But, unfortunately, the trimmer heads during operation over time become unusable. Some malfunctions can be eliminated with your own hands, and some require a complete replacement of the mowing head.

Trimmer Coil Device

Mowing heads for trimmers come in many designs – both simple and complex. The picture below shows semi-automatic trimmer head from the Husqvarna lawn mowers (Husqvarna) disassembled.

This type of head is present in the configuration of most lawnmowers and trimmers, such as Stihl (Stihl), Patriot (Patriot), Champion (Champion), Bosch (Bosch), Huter (Huter) and others. The mower head is quite simple. It consists of the following details:

  • Mowing head base;
  • Button for semi-automatic cord feeding;
  • A bobbin (reel) into which the fishing line is refueled;
  • Spring;
  • Eyes – through them the fishing line comes out;
  • Trimmer head cover;
  • Fishing line (cord).

There are also simpler trimmer heads shown in the following photo.

All these attachments do not allow changing the length of the fishing line in semi-automatic mode (after pressing the button). In the event of a break in the cord, you have to stop the mower and change it manually.

Basic coil faults

Trimmer users and lawn mowers often encounter a problem with a semi-automatic mowing head. Coil malfunctions can be as follows:

  • The fishing line does not automatically extend;
  • The cord spontaneously exits the coil.

The fishing line does not automatically extend

If the line does not lengthen with a light touch of the trimmer coil button on the ground, the reasons for this may be as follows.

Option 1 – a bite occurred, i.E. Clamping cord between turns. This problem usually occurs if the user wound the fishing line on the reel unevenly, with the intersection of turns, or wound it with insufficient tension. In the latter case, when the mowing head rotates at high speeds under the influence of centrifugal force, the cord begins to drag out, as a result of which it is possible to twist the fishing line. To fix the problem, you will have to disassemble the coil on the trimmer and rewind the cord correctly, that is, in even turns with good tension.

Option 2 – too short ends protrude from the head. The fishing line may not come out when it hits the ground, if its ends protruding from the head are of insufficient length (short). In this case, centrifugal force is not enough to stretch the line. Therefore, it is necessary to stop the unit (turn off the engine or disconnect the trimmer from the mains) and pull out the fishing line manually by first pressing the button.

Option 3 – fishing line soldered inside the mowing head. This causes the coil to stop and not spin when the button is pressed. Basically, this happens for several reasons: poor quality of the cord, overheating of the coil during continuous operation of the unit, impact of fishing line on solid objects.

  1. In the first case, the cord of third-party manufacturers can be made of low-quality and low-melting materials that do not withstand mechanical and thermal stress. Therefore, preference should be given to “branded” fishing lines.
  2. But, if you nevertheless acquired a fishing line of unknown quality, and it often gets soldered during operation, then you can follow the example of some users who, after refueling the cord into a coil, moisten it either silicone grease (from spray can), or mineral oil. This procedure greatly reduces the likelihood of soldering between each other turns of fishing line.
  3. Also, the fishing line can be soldered if during mowing it hits a solid object (stone, fence, dry branch, etc.). As a result of this, it stretches a little and is pulled back into the head at high speed. The cord heats up due to friction, and its coils stick together. The only thing that can be done to eliminate this malfunction is to open the trimmer coil and rewind the fishing line.

Cord spontaneously lengthens

There are situations when the trimmer user notices very fast consumption of fishing line. However, he never hit a button on the ground to lengthen the fishing line. The reason that the fishing line spontaneously lengthens, cutting off a special knife on the casing of the device, can serve lack of spring in the mowing head. Often, novice users of mowers, trying to charge the fishing line into a reel, forget to install the hold-down spring in the head, or even lose it when the lid is opened, and in the future, they are not even aware of its existence.

How to remove the reel and replace the fishing line

Owners of trimmers, mostly novices, are confused, bordering on panic when it becomes necessary to change the cutting tool or fishing line in the reel. Very often, when trying to unscrew the mowing head, users simply render it unusable, not suspecting that it is unscrewing in the opposite direction. To prevent this, if you need to replace the tool, it is recommended that you read the step-by-step instructions below.

  1. Before putting the fishing line into the reel, turn off the engine of the lawn mowers or de-energize the trimmer to avoid injuries that might occur if the cutting tool is accidentally started to rotate.
  2. Unscrew the nozzle attached to gear shaft. To do this, the shaft must be locked by aligning the holes on the washer and on the axis, and inserting a metal rod or screwdriver into them.
  3. Unscrew the nozzle. You should know that the thread on the shaft is left. Therefore, twist the trimmer coil to the right, that is, clockwise.
  4. Disassemble the mowing head. Most often, the head cover is attached on clips. To remove it, you will need to drown these clips into the body, squeezing the edges of the lid. If your trimmer has a semi-automatic mowing head with a button on the bottom, disassembling the nozzle should be done carefully, since you can lose the spring, which sometimes flies out when the cover is removed.
  5. Cut the required amount of fishing line. Usually its length is 5 meters. Use a cord of the diameter specified in the tool manual. It is not recommended to exceed the maximum diameter of the fishing line, as this will lead to increased engine load and higher gas mileage.
  6. Find the middle of the cord segment, folding it in half. You will get a loop.
  7. Cut through the coils special grooves (there may be holes). Insert a loop from the fishing line into this groove.
  8. Wind the line onto the reel by turning it counterclockwise. It is necessary to refuel the cord as evenly as possible, the turns should lie down without overlapping and with good tension. When the winding is finished, leave the free ends of the fishing line about 20 cm long and fix them in the grooves located on the sides of the reel.
  9. Assemble the mowing head. Before you finally assemble the nozzle, do not forget insert spring and washer (if available). Install the coil in the housing, and thread the ends of the cord through holes or eyes.
  10. Put on the cover and fix it with the latches.
  11. Screw the nozzle back onto the gearbox shaft, also locking it with a screwdriver. Spin the trimmer coil to the left (against the clockwise arrow).

Is it possible to make a coil on a trimmer with your own hands

  1. Take a piece of plywood or textolite and draw a circle on it with a diameter of about 14 cm.
  2. Cut the disc with a jigsaw or hacksaw for metal.
  3. Drill a hole in the center of the disk that matches the diameter of the gearbox shaft. Before installing the disk on the shaft, do not forget to put the washer on it.
  4. On the edges of the disk, you can screw small corners or make 1-2 holes on opposite sides. They will serve to refuel fishing lines in them.
  5. To fix the fishing line, several screws can be screwed into the plywood.

Such a homemade mowing nozzle is mounted on a shaft with a nut. Tighten or unscrew the nut without fixing the shaft will not work. To replace the cord, it will be enough to release the screws, insert a piece of fishing line of the required length and press it again.

Also, a mowing nozzle for attaching fishing line to it can be made from a metal sheet. How to do this, you can understand from the next video.