A lawn mower is a useful tool in the household, but the blades of the machine are easily dull. A simple solution to the problem will be an expensive repair in a service center, but it is much more profitable to learn how to sharpen a knife for a lawn mower with your own hands.
The main stages of work
First you need to drill a through hole in the center of the plate, and cut a thread into it for the diameter of the stud. Next, bend four strips of metal at an angle of 90 degrees. We weld two of the blanks to the plate, and the remaining two to the previously welded strips, and additionally connect them using another strip.
We weld a metal rod to the end of the stud so that it is more convenient to unscrew and twist the fixture. We clean the resulting design with an angle grinder, after which we cover with 1-2 layers of spray paint. We cut the hairpin to size and screw it into the hole in the plate, putting on the nut first. The fixture is now ready for use.
Turn the lawn mower on its side, lock the cutting knife of the lawn mower and fix the frame of the homemade device to the body due to the rotation of the stud. See the video on the site for a step-by-step process of manufacturing and assembling this design.
Sharpening the knife rotary lawn mowers
Rotary devices include:
Gasoline mowers;
Electronic lawn mowers. wire and battery.
In their equipment, two-bladed knives are used mainly, less often a knife with 4 blades. The sharpening technique is the same for all types, and does not have any differences.
To do the job you need:
Work gloves;
Spanner or socket wrench of the corresponding size;
A set of rattles, an abrasive whetstone, or an electronic tool-grinding tool.
Before sharpening the knife of the mower, you need to perform several preparatory operations:
Prepare the lawnmower to remove the knife. In particular, owners of petrol models of lawn mowers need to take a close look at this step. It may be necessary to drain the fuel, oil;
Knife sharpening lawn mowers from Lenfilm studio
We tried our best. If you are not very happy, then check out our website. There we sorted out the “flights” detail.
Cleaning and editing
When the knife is removed, it must first be cleaned of adhering dirt and hardened herbal juice. The easiest way to do this is to use a metal trim. The strip of the knife should be clean from all sides: not to a metallic luster, but without the smallest adhering fragments.
Often, when hard objects such as stones and wood chips get into the work area, the blade is very noticeably deformed. Most blades themselves are not straight, but the cutting edge and strip 10-15 cm from it should be examined for the presence of local tubercles and curvatures. This is done with a short straight ruler.
You can straighten the blade with an ordinary hammer, whose edges of the striker are slightly rounded. The knife is laid on an even massive support (anvil), then, with weak strokes, the metal is given the correct shape. You need to edit the knife, starting from the edges of the curved section, gradually moving towards the center. The curved body of the blades is a small problem, but it is very important that the cutting parts are straightened into one straight fishing line. You also need to check the throwing blades, which often bend over from the impact. If the blades on different shoulders of the knife are bent at different angles, this will worsen the air flow and the mowed grass will not be properly mulched.
Adapter do-it-yourself mower knife
Lawn mower knife adapter MATRIX Turbo 50 do it yourself. After the destruction of the unusual knife adapter MATRIX.
Sharpening a lawn mower knife from the Lenfilm studio
Adapter lawn mower knife Matrix turbo
Unfortunately, Matrix-direct company has finished supporting this product. In the service centers located in the list.
Turn the mower over to access the cutting tool;
Fix the knife with a wooden block;
Using the right tool, usually with a socket or cap wrench, unscrew the attachment points of the knife;
Take off the knife itself.
After cleaning the knife from adhering weed, dirt, you can proceed directly to sharpening.
To sharpen the knife of the lawn mower, you will need a stable base. a table or a workbench, on the surface of which you can comfortably position and fix the knife for final sharpening. A balanced option. if you have the opportunity to fix the knife in a vice.
When performing work, note that the working part of the knife is hardened, you should try so that the impact on the blade is minimal and maintain the angle of sharpening lawn mower knife.
If the working parts of the knife have no damage. burrs, chipping, then you can limit yourself to editing the blade. Why you can use an abrasive bar or a file with a diamond coating. To remove a large amount of metal is not required, and you can do with a "thin" tool.
Video: How to Change Oil in a Lawn Mower
If the knife blades are damaged, before sharpening, they must be removed with a rough file, on an emery wheel or with an electric tool with an abrasive nozzle.
If you are doing the work with a file or an abrasive block, then sharpening is done from the center of the knife to the edge. The movement of the instrument is “away from you”. After completing the work, it is necessary to check whether the balancing of the knife of the mower has changed.
A sharpened knife can be installed on a lawn mower and begin mowing the lawn.
Bosch rotak 37 LI how to change a knife on a lawn mower
Bosch rotak 37 LI how to change knife on the lawn mower.
Sharpening the knife of a spindle lawn mower
Drum (spindle) lawn mowers are equipped with a knife block. a formed drum, in which several curved blades and a fixed straight knife are installed. It may seem that it is very difficult to sharpen such a knife, but it is not. You don’t even have to remove the spindle.
To sharpen the spindle knife you will need abrasive. sandpaper, preferably waterproof.
From a sheet of paper, it is necessary to cut a strip in width greater than the width of the fixed knife by 1-2 mm and stick it on the fixed knife of the lawn mower using double-sided tape, with the abrasive coated side up.
Then bring the knife drive into action. Hand-held lawn mower. ride on a flat hard surface several times, if you have an electric drum mower then connect it to the network, turn it on and let it run for a short time, just 1 minute is enough.
Before using the mower, be sure to remove the sandpaper from the fixed knife.
As you can see, sharpening a knife of any lawn mower is not so difficult and every owner of this type of garden equipment can do this job.
Bosch rotak 37 LI how to change a knife on a lawn mower
Bosch rotak 37 LI how to change knife on the lawn mower.
Tatyana65, I have a Honda mower, she was in her fourth year. A detailed annotation on sharpening a knife is attached to it. larix wrote everything right. Although it is safer and more convenient to remove the knife, which, by the way, is attached with 2 bolts. We check the balancing by “hanging” it on a screwdriver.
Naturally, one should not, on ability, run into pebbles and other objects. this very spoils the knife.
Editing Edges
When the blades are sharpened, they need to be fixed. This is done using a piece of moisture-resistant sandpaper with a grain size of about 600-800 grit. The paper should be moistened with water and rolled into a cylinder with a diameter of 100–150 mm.
Editing aims to remove the slightest burrs and flakes, due to which the thinnest edge of the blade can wrap. The emery paper rolled into the cylinder should be slightly pressed to the plane of descent and stretched in a smooth motion from the grain. It is also recommended to make a smooth shift from the center to the edges.
When removing descents and sharpening, all manipulations were carried out with only one side of the blade. In the process of dressing, the knife is also processed from the back. Here, the paper is pressed almost close to the body of the knife, but with a slight slope towards the edge. The effort of pressing the paper during editing is very small, but the movements need to be done quite a lot, trying to eliminate large scratches on the shiny descent that remained after sharpening.
For reference: You can also sharpen the lawnmower’s knife with a rivet, similar to a conventional manual scythe. True, this requires the presence of a special device. a headstock, as well as a specific skill. But then with this method of sharpening, it is not necessary to balance the knife.
Read the same
I always sharpen the knives myself. the service centers are far away, and the whetstone is nearby. The previous relatively low-power electronic mower had to be sharpened quite often; the edges of the grass were shagged differently. So far, we have sharpened a stronger gasoline 1 time per season. it can be seen that it takes it "pressure". The first time it was very difficult to remove the knife. it sticks to something or that, but the spouse only from the third call is special. unscrewed the key. And on the electronic, I was driven by pliers without troubles.
I took a spare knife in the Lawnmower Man, but my husband took off an old one and sharpened it, worked for a while, all the while hoping that the mower would be unbalanced and I would buy the latest one. nothing had come of it, so far I had been using the old one, and she had fed up with it for at least 4 years.
To some extent, the danger of a small imbalance is a myth. Look at the knife, it’s not so much news that it sticks to the film, but not moderately. And nothing harmful to happen.
But if you take it off and sharpen it on a grinder, then you’ll definitely get an imbalance, the grinder removes metal shamelessly.
Personally, I sharpen either with a diamond rattle (very good for tool steel and removes a minimum). How to remove a knife from sharpening a knife of a lawn mower can also be a riveting by analogy with the video. All. Or, if I launch in very other words a Dremel-type mini drill, it can also be sharpened very neatly. It is not necessary to sharpen a knife completely until the sharpness, the main thing is that there is an obvious angle, and not roundness.
What makes it difficult to check the balance by putting the knife over the central hole on the stick. if it hangs evenly. in equilibrium, if one side pulls down. it is unbalanced and needs a little take off. Naturally, with this method, the knives grind faster. but it seems to me that buying a couple of spare ones and replacing them as they are grinded is more economical than dragging the service to the other end of the town every time and paying for sharpening (the only time I did this, they took 300 rubles from me, it was about 5 years ago). How to install a 2-blade knife on a Stihl fs 55 lawn mower. Video instruction how to change the mowing heads of a brushcutter from a reel (fishing line) to a knife. You just need to calculate how much a knife costs and how much. a trip to the workshop.
I don’t like sharpening rattle or whetstone. it’s long and boring. it’s a real pity. You can also meditate on another work. weeding, for example. IMHO
Vaska, I don’t sharpen the knives either, but change them, but I’ll tell you about the imbalance. Putting a knife on a stick and aligning it you will get only a static balance, you can’t check the dynamic balance at home, and specifically it gives the most adverse consequences for the motor.
Rom165, I want to clarify. I just sharpen the knives. but myself, with an electric grinder. And the rest I agree. they used the electronic mower for 6 years, it already began to wear out the case (plastic). but it worked properly and was given “in good hands” after acquiring gasoline in working condition. how to wind a fishing line for testing a lawn mower with the function of a Yakut knife from. Over the years, 2 knives were used interchangeably, and did not have time grind off with a sharpener before discarding. And they mowed a lot. hundreds of grass stands. There was an imbalance. there was not. I do not know.
I’m reporting. at work, our craftsmen sharpened a knife, checked for imbalance, gave and pronounced it. use it. I watched closely how they sharpened, in order to sharpen later the knives myself. how to install a 2-blade knife on a Stihl fs 55 lawn mower. Video instruction, how to change the mowing heads of a brushcutter from a reel (fishing line) to a knife. I can use an electric sharpener. And it turned out to be so simple to sharpen knives that I and my wife will not even strain
Balancing check
Before installing the blade back, you need to make sure that its shoulders have at least about the same weight. Otherwise, vibration will occur during operation, which will not affect positively the spindle durability.
Balancing is carried out mainly for double-sided single and compound knives, four-blade is not so much prone to imbalance. To check the knife, you need to clamp a smooth bar in a vise in a horizontal position. A blade is put on it through the hole in the center, after which attempts are made to install it strictly horizontally. If one of the shoulders weighs significantly more than the other, the knife will steadily turn in one direction.
The equation for the weight of the shoulders is carried out by grinding a small amount of metal from the back of one of the shoulders of the knife. It is not necessary to achieve ultra-precise balancing, however, the knife must be held at least for a few seconds in a strictly horizontal position. When the balancing is done, you can put the knife in place and finally update the look of your lawn.