DIY Powerful Lawn Trimmer From an Angle Grinder

The idea of creating a small lawn mower came from the need to get rid of weeds in his yard and garden. Due to the fact that I have a small area and do not need to mow the lawn often, I did not buy a new lawn mower from the store. I only do this two or three times a year. Also, I don't see the point in buying a cheap lawnmower that will probably fail quickly. And it makes no sense to buy a high-quality and expensive device because it will rarely be used anyway.

I had an old grinder lying around that I didn’t mind turning into a lawn mower. There were some more spare parts from non-working angle grinders from which you could also make something. Therefore, I left the idea of connecting an electric motor to a gearbox from an angle grinder for future experiments. I needed to quickly get rid of the weeds and grass in my yard. Therefore, the easiest and most affordable way is to use an electric grinder. I really didn't want to do it manually. Especially since I already had the experience of cutting grass by hand with a simple hand scythe.

Such an electric mower can always be disassembled and used as an angle grinder for its original purpose. I tested the lawnmower last season and was satisfied. By adjusting the engine speed, it is possible to adapt the lawn mower to the different vegetation on your site. For example, when you mow weeds, you need more power, so the electric motor runs at maximum speed. And for grass or other delicate plants, the power can be reduced. This is very convenient in practice because you can control the process! This lawn mower is also very light and can be held with one hand for a long time. With such a tool, it is easy to perform work in the yard and also have great fun!

Electric components:

• Angle grinder 1000 W/11000 rpm
• Dimmer, up to 800 Watts
• Electric switch
• Electric socket
• Electrical wires and connectors
• Thermotubes, electrical tape
• Differential circuit breaker 10mA/220V (optional)

Materials:

• Wooden bar: 1200 x 30 x 20 mm
• Furniture corner
• Metal corners
• Spacer fasteners with M12 thread
• M6 bolt – 3 pcs.
• Screws
• Trimmer line
• Plastic nylon straps (screeds)

Tools:

• Grinder machine
• Renovator saw Multi-Tool Kit
• Drill machine
• Electric wood burner (optional) 
• Quick-release vise
• Wood saw
• Roulette
• Calliper
• Drills of various diameters
• Blade knife
• Sand paper
• Marker
• Scotch tape
• Screwdrivers, pliers, cutting pliers, and other tools that can be found in any home workshop

In this diagram, I show the general arrangement and wiring diagram of the trimmer. Here are the approximate dimensions of the design elements of the device: Based on this diagram, you can get the idea of making a DIY trimmer.

The concept of creating a lawn mower was that it would be a simple device made from available materials. I began to look in my workshop for suitable materials for this project. The original goal was to make a tool from what I already had and not buy additional parts. At the same time, I wanted the design to be not only simple but also lightweight. The weight of the tool is of great importance when working with it. It will have to be held in your hands for a long time. I was thinking of using an aluminium profile or tube for the lawn mower frame. But such a material complicated the design, so I came to the conclusion that wood is better suited for this purpose. The wooden block is not only light but also easy to process.

An important point in the manufacture of lawn mowers is the fastening of the grinder. The tool must be well fixed due to the fact that it must work at high speeds. Therefore, a metal bolt from spacer fasteners with an M12 thread is just right for fixing the motor. I also used metal corners and plates, as well as ordinary self-tapping screws.

So, all structural elements can be easily found in your workshop, as well as in any hardware store.

I used a block of wood as the main mower holder. I chose the lightest of several wooden blocks. Furthermore, I decided the dimensions experimentally. The thickness of the beam is approximately 18 by 28 mm, and the total length is 1.17 m. You can use an aluminium profile, but in this case, you need to take care of additional fasteners. On a tree, it is very easy to change the location of the fasteners using self-tapping screws. And in general, it is very pleasant to work with a tree!)

First, I sanded the block with a grinder. Also, this can be done by hand using sandpaper or a jointer. During work, you need to monitor the location of the fibers on the tree and grind in their direction. In order to secure the beam to the surface before processing, I used a quick-release vice.

Also, do not forget about safety measures during wood processing! Protective equipment must be worn while working!

I remember a case when a colleague polished off part of his finger. Therefore, do not neglect the safety measures for working with power tools! After processing a wooden block, it must be cut to length. It is necessary to take into account the height of the person who will work with the tool. I am tall, so the length of the pole is about 1.2 m. It is also necessary to take into account that the wooden beam is dry and free of defects.

In addition to the main beam, I used another smaller wooden beam that will be attached to the main one. I will talk about it later.

In order to make it convenient to work with a lawn mower, a wooden beam must be fixed at a certain angle with respect to the angle grinder. This is an important point for the whole structure to be strong. To do this, I cut off one end of a wooden beam with a hacksaw. The cutting angle should be approximately 65°. I chose this criterion experimentally, so the cut angle can be varied. This step does not have to be repeated exactly. You can find another way to mount the tool. One way or another, you need to fix the grinder as rigidly as possible.

A protective cover is needed to protect a person when working with a lawn mower. The trimmer line rotates very quickly and can sometimes break. Also, during rotation, small pebbles can come across and fly off to the sides. Therefore, it is better when working with a trimmer to wear special equipment for protection. And even when the grinder is working, you need to ensure free air circulation to the device.

I used a simple plastic bucket lid to make the protective cover. The lid diameter is approximately 28 cm. First, you need to mark the middle of the lid with a marker. After that, determine where the grinder will be located. To make the hole, I used a pen bit because it made it easier to drill through the plastic. I also measured the length between the holes for attaching the grinder using a calliper. The length between the bolts is approximately 35 mm. After that, I drilled a hole for the bolts with a simple metal drill with a diameter of 7 mm. To level the plastic, I used an electric burner on wood. With such an apparatus, it is very easy to process plastic parts. The grinder must be fixed with M6 bolts to the base of the casing. I also used a plastic tie for additional fastening of the device. To do this, I made small longitudinal holes on both sides of the grinder.

Later, after testing the trimmer, I changed the shape of the plastic cover by cutting out a piece of plastic from the front of the device. You can use another material to make a protective cover, such as aluminium composite. The protective casing can also be made of iron, but it will make the design of the lawn mower heavier.

In order to easily operate the electric trimmer, you need to install some electrical components. First, you need to be able to conveniently turn the device on and off. To do this, I found in my workshop a very compact switch that can be installed on the trimmer handle.

The grinder that I use as a motor with a gearbox has very high speeds to rotate the fishing line. The angle grinder is used to work with discs with a diameter of 125 mm. The power of the device is 1000 W. The maximum spindle rotation is about 11000 rpm. At the same time, the device is designed to be connected to a 220 Volt / 50 Hz network.

In order to be able to control the speed of the grinder, I used a 220-volt AC dimmer, up to 800 Watts. This is a very simple current regulator based on the control of an electronic triac. In order for the triac to withstand power up to 1 kW, I added another aluminium radiator. Such a heat sink will prevent the electronic component from overheating and burning out. You can also change the triac in the electronic device of the dimmer to a more powerful one. You can also find such a power regulator in a power tool. In this case, there is a problem with the body's attachment to the trimmer handle.

Therefore, I left the usual trimmer, using a standard housing from household electrical outlets to install it. In order to connect the grinder, I used an additional outlet that will be attached to the lawn mower. Such a connection makes it possible to easily disassemble the trimmer and use the angle grinder for other purposes. Also, in case of any issues that may arise when working with the device, you can easily turn off the equipment by removing the plug from the socket.

One important item for protection against AC electrical current is the differential circuit breaker. The machine turns off the load at the slightest change in current in the circuit. This means that if the insulation of the conductors is poor or if moisture gets on the lawn mower, the machine will be de-energized from the electricity circuit.

If you prepare all the necessary components, the trimmer assembly takes very little time. I spent several hours assembling the device. I think it took more time to find the right parts.

So, in addition to the wooden beam, you need to make one more detail, to which the trimmer handle will be attached. I used a piece of round wooden handle from a mop (40–50 cm). On this bar, I fixed the furniture corner, which is usually used for attaching shelves. An additional plastic case will make it easier to grab such a handle. In addition, I made a ring out of a metal plate in order to put my hand through it and grab the trimmer handle. This part is actually very convenient to use! I came up with it originally for other purposes. Such a life hack turned out to be just the thing for a homemade trimmer. Wooden parts are fixed to each other with self-tapping screws. Additionally, we used adhesive tape for greater reliability in connections.

Now you need to attach the grinder to the wooden beam. To do this, I used a metal anchor that can be screwed into the base of the device. All this must be fixed to a wooden bar with self-tapping screws and metal corners, as can be seen in the photo.

For the electrical part of the trimmer, you need to attach a plastic box for the speed controller to its body. At the end of the trimmer handle, you need to install a socket for connecting the grinder cable. This step can be skipped if the grinder wire is extended with an extension cord. The cable from the grinder must be twisted around a wooden beam and secured with tape or nylon ties.

The trimmer device is connected in series with the outlet. All conductors are insulated and covered with a plastic case. The switch must be fixed with adhesive tape to the trimmer handle so that you can easily control the device. I installed the dimmer on the left side of the device. But after testing, it seems to me that it is better to attach it to the right.

In order to prevent the cut grass from getting inside the grinder's motor, you can use a plastic mesh. This mesh is sold at hardware stores. This additional filter will extend the life of the grinder. You can also add air intakes made of plastic. In order to protect the motor of the mower, several filters made of a finer mesh can be used.

So, it remains to check the reliability of fastening the grinder and other elements of the trimmer. To make a homemade trimmer, I used the simplest and most affordable materials. The main goal was to make such a device as quickly and easily as possible! During the operation of the trimmer, you can always add some additional elements to improve the design.

There are many types of lawn mower lines. Cord differs in shape and cross-section: round cord, square cord, reinforced, as well as a fishing line with a multi-angle section. From my own experience, I can say that a fishing line with a square section, as well as with corners, copes better with weeds such as deadwood, burdock, or hogweed. In order to mow the lawn, that is, simple grass, the simplest braided fishing line of a small section is suitable.

I have tried different cords and lines of different diameters. From shoelaces to nylon ties. I decided that for a trimmer made from a grinder, a plastic cord with a large cross-section is best suited. So I use about 5 mm of line for weeds and other thick plants.

In order to install a fishing line on a trimmer made from a grinder, you need to pass it through the hole in the head. First, I measure about 50–60 cm of the length of the fishing line and cut off a few pieces in reserve. After that, I fix the fishing line with the key from the grinder, but without twisting it too much. If it is strongly flattened, it will quickly tear! You can also use two pieces of fishing line so that four pieces come out of the trimmer. This will increase the efficiency of the lawn mower.

When working with my homemade trimmer, I noticed that due to the very high engine speeds, you can quickly break the line. Therefore, depending on the section, it is necessary to adjust the rotational speed of the apparatus accordingly. When using a plastic fishing line with a diameter of about 5 mm, one cord is enough for me to cover several acres of land. The cord wears out gradually, depending on the plants you are mowing.

Warning! Making and using a homemade trimmer can be dangerous! Therefore, everyone makes the decision to make a homemade trimmer from a grinder, which everyone takes for himself. I do not bear any responsibility for possible consequences when working with such a device.

For such a trimmer, you need to use only plastic fishing line! It is very dangerous to use a cable or other metal disc not intended for mowing grass! The metal pieces of a metal rope can be much more dangerous than plastic fishing line.

As a protective measure when working with a trimmer, I use special, durable shoes. Be sure to wear special clothing to protect your legs, as well as a protective mask or goggles.

To protect your hands, you can use special gloves that are sold at any hardware store. You can also use protective earplugs. These simple safety measures will save you in the case of a machine breakdown or other unpredictable incidents! It must be remembered that the trimmer is connected to an alternating mains voltage. Therefore, it is very important to use a quality waterproof cable or extension cord. The plug and socket, as well as the housing where the speed controller is installed, must comply with the moisture protection standard (for example, IP64 and higher).

All electrical equipment is best connected to the electrical network through a differential machine that will turn off the electricity in case of danger! These simple safety measures must be followed!

My homemade trimmer passed the test on my site. I've been using it for the second season now. The trimmer turned out to be much harder than I originally expected! I didn't think it would last this long. Unfortunately, the plastic protection did not pass the test. I changed its shape by cutting off the front part, but at the end only the part that is located below the angle grinder remained. I think it's best to use aluminium composite or another material as a protective casing.

When working with a trimmer, you need to ensure that the grass does not clog the axis of the grinder motor. It is advisable to disassemble the device at least once a season and clean it from the remnants of vegetation. At the same time, you can change the filters and monitor the commutator brushes of the electric motor rotor. Based on the technical instructions for operating the angle grinder, you can also change the lubricant in the gearbox of the device.

Anyway, the trimmer works great and keeps my yard and garden clean. Of course, a lot can be improved in the mower's design. But the task that I initially set was completed!

Thanks for your time and attention to this topic! 🌼

My friend kindly helped me and tested the trimmer.)