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8 Angle grinder basics you should know – best beginner tips


An angle grinder is standard equipment in metalworking shops, woodworking shops and construction sites because of its versatility and time-saving.

However, working with a grinder is not without risk. That’s why knowing a few angle grinder basics will help you get to know this great tool better and use it more responsibly.

This article will teach you the most important angle grinder basics, so read them carefully before you turn on the switch.

Angle grinder basics – parts of an angle grinder

Before we get into the angle grinder basics, it’s important to understand how to identify the various parts of this power tool.

If you’re new to the disc grinder, knowing and naming all of the parts will help you understand everything.

Examine the image below, which depicts the most important parts.

Angle grinder basics - Angle grinder parts - DEWALT Angle Grinder Tool
Angle grinder basicsAngle grinder partsDEWALT Angle Grinder Tool

What is an angle grinder

An angle grinder, also sometimes referred to as a side grinder or disc grinder, is a fast rotating hand-held power tool used for cutting, polishing, or other uses.

The way in which a grinding tool cuts through the material is by using the grinding wheel at a high speed to cut the material away in an abrasive manner.

Angle grinder basics - Makita 9564CV 4-1:2-Inch
Angle grinder basicsMakita 9564CV 4-1:2-Inch

This power tool was originally developed as a hard sanding disc tool, but over the years, due to the high speed, a wide variety of cutters and attachments have been developed for applications other than cutting alone, later more about the uses of an angle grinder.

Disc grinders can be powered by either an electric (corded or cordless) motor or compressed air. This motor powers a bevel gearbox, which houses a grinding wheel. When these grinding wheels wear out, they are easily replaceable; more on that later in this article.

For safety reasons, disc grinders generally have an adjustable guard and side handle for safe two-handed operation.

The gearbox is usually made of cast iron so that a sturdy housing is obtained for a perfect transmission through the gears. The back system is usually made of hard plastic, phenolic resin or medium-hard rubber, depending on the desired degree of flexibility.

What is an angle grinder used for

Originally, disc grinders were made to cut through materials or to remove excess material from a piece.

Later, when people realized the capabilities of this high-speed power tool, many attachments have been developed that can handle various applications, next to cutting, such as sanding, polishing, milling, rust removal, etc.

Different types of wheels are available for all these tasks, such as cutting discs, diamond cutting discs, grinding discs, abrasive discs, wire brush discs and polishing pads.

Thanks to the large bearings that the angle grinder has, it is possible to absorb heavy lateral forces that arise during sawing. This is what makes this tool so powerful and versatile compared to other tools that couldn’t provide these benefits.

Angle grinders are common in metalworking, woodworking, and construction. They are frequently found in both professional and do-it-yourself workshops.

However, finding the right grinding tool for the job can be difficult. There are numerous brands and key factors to consider. To find the best angle grinder, consider the disc size, power source (corded, cordless, or pneumatic), and motor power. Keep an eye on my website for a future article with more information on finding the right disc grinder.

What is the rpm of an angle grinder

You might not expect it, but angle grinders with the capacity for small discs have a higher speed than larger models with larger discs.

The speed of disc grinders is expressed in rotations per minute (RPM). You should know that the angle grinder RPM is expressed in terms of no-load speed. This means that the RPM of your grinding tool is the fastest rotation it can generate without a disc installed.

A medium-sized angle can generate more than 8,500 RPM, whereas a larger angle grinder has an RPM of around 6,500. A smaller angle grinder will produce more speed, while a larger disc grinder will produce more power.

Medium-sized angle grinderLarge angle grinderPneumatic angle grinder
Disc size115 – 125 mm / 4-1/2″ – 5″180 – 230 mm / 7 – 9″115 op to 230mm / 4-1/2 up to 9″
RPM8500RPM6500RPM11000 – 23000RPM
Power700 – 1700W2000 – 2600W500W
Weight2 – 2,5kg / 4,4 – 5,5 lbs5 – 6kg / 11 – 13,2lbs1 – 1,5Kg / 2,2 -3,3lbs
Angle grinder basicsAngle grinder RPM chart

What is a paddle switch on an angle grinder

Many older machines, especially smaller disc grinders, are equipped with a lock switch. If you have watched my YouTube videos, you can see that I have one like this.
If you’ve ever operated a machine like this, you’ll be familiar with that hard-to-slide switch on top of the grinding tool that, once clicked, spins the disc grinder.

Keep in mind that this can create a very dangerous situation. In the event of a disc grinder accident, the switch will not turn off and this tool will continue to run, possibly causing even more damage.

Today, many of these tools have a paddle switch on the handle instead of a locking switch.
You should think of a paddle switch as a kind of lever that is mounted on the handle of the angle grinder. By pressing a small safety button you can depress the lever which causes the tool to rotate.

When you grab the handle, you also hold down the switch that turns the tool on. If you lose control of the tool and the paddle switch is no longer pressed, the grinder will turn itself off.

Holding down this paddle switch to use the angle grinder requires no extra effort as this paddle switch is located on the handle. In addition, this provides enormous safety benefits in the event of an emergency.

Angle grinder basics - paddle switch - Makita 9557PB 4-1_2_
Angle grinder basicspaddle switchMakita 9557PB 4-1_2_

How to switch on an angle grinder

Turning on an angle grinder depends on the model, but there is one big basic rule and that is to hold the machine firmly before turning on the switch.

To have a firm grip on your machine, it is therefore recommended to mount the handle so that you can hold the tool with both hands.

Once you have the tool in place you can either slide the switch to the on position or press the paddle switch.

Angle grinder safety tips

A grinding tool is a pretty dangerous piece of equipment to work with, but I don’t think I need to tell you this. That is why it is good to think about a few actions you can take to make this tool as safe as possible. Also, make sure you have a first aid kit in your workshop in case of an emergency.
Learn how to make your own first aid kit in this article.

That’s why I made a short list that you can think about before you get started with an angle grinder. Soon I will make a separate article about this where I will go into more detail on these points, so keep an eye on my website or subscribe to the newsletter.

  • Always wear the correct Personal Protective Equipment (PPE)
  • Match the RPMs to the compensation of your grinding wheel
  • Use the correct disc size
  • Always make sure that you tighten the discs properly.
  • Before starting, inspect the abrasives for loose or broken parts.
  • Let the tool run without cooperating first and see how the disk responds.
  • Use the safety caps as designed and do not remove them
  • Please leave the machine original and do not tinker with it or try to modify this tool.
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How to use an angle grinder

Use a wire brush for cleaning or rust removal.

Before you begin, secure the work securely with clamps or a vise.

The second thing to do before turning on the switch is to see which direction the brush is turning. Make sure the brush turns away from the edge and never towards the edge, otherwise the brush may catch on the edge and cause kickback.

Now switch on the tool and hold it firmly while pressing the wire brush lightly on the metal. Do this under light pressure and build up the pressure as you notice how the machine reacts.

Sharpening knives

To begin, ensure that the object to be sharpened is securely fastened to your workbench. Then, to sharpen, select an appropriate grinding wheel.

Before you begin, check the angle you will be sharpening with the tool turned off. Turn the grinder so that the blade is facing the edge.

Start the grinder, allow it to come to a stop, and then lower it gently against the blade. By grinding back and forth, move the sharpener over the work. Examine the blade after each length to ensure that the proper angle was used.

Keep making the same movements until you have an even edge that is sufficient when sharpened in each place.

Please note, due to the high speeds a grinding tool is capable of, it is easy to overheat a metal blade. You can see that when the metal turns blue-black. This will greatly weaken the metal and become blunt faster.

To prevent overheating, you can do two things: you can slightly reduce the pressure you exert, and don’t leave the grinding wheel in one place for too long, but keep it moving. Leave enough time between different actions, so that the heat does not build up too much.

Cut tiles, stone and concrete

To do this, it is best to mark the cut accurately on both the front and the back of the tile. Make a shallow cut at the top first with the diamond blade, then flip the tile over and complete the cut.

The grinding wheel is a much better choice for notching or cutting around electrical outlets than a tile cutter. If you are going to tile, it is therefore best to have a small angle grinder on hand for these tasks.

Cutting tiles involves creating a lot of fine dust, so make sure you have a suitable dust mask and protect yourself.

Cut bars, rods and bolts

To do this, you mount a metal cutting disc in your grinding tool. a cutting disc is a thinner disc that makes it possible to make quick cuts.

Clamp the metal firmly on your workbench or in the vise. Lower the cutting wheel through the metal so that the weight of the tool can do most of the work. Let the short end fall freely to prevent the blade from getting stuck.

Glowing spatters are produced when metals are ground. Check that there are no combustible materials near the area where you will be sharpening. Before I leave the workshop, I always wait a little longer and carefully observe it. Smoldering material can linger for a long time before it begins to burn.
Related article: how to use an angle grinder

How to change disk on an angle grinder

Before disassembling and assembling the new disk, make sure the tool is unplugged. You don’t want the switch to be accidentally turned on while your hands are against the cutting element.

Verify that the element purchased is properly sized and meets the requirements specified by the equipment manufacturer.
Never mount discs where the spindle hole does not match the spindle of the tool. Follow the manufacturer’s instructions in the device manufacturer’s instructions for efficient and safe mounting of the disc to the angle grinder.

There are two different systems for mounting discs: with a wrench or tool-less mounting. The mounting is done in a different way, which I will describe below.

Mounting a disk with a key

To begin, use a special double pin wrench to loosen the clamping nut. The wrench, which resembles a flat wrench with two small tabs on the end, is usually included with the tool.

A small button (the spindle lock) on the back of the grinding tool will lock the disc. It is critical at this point to determine the direction of rotation of the blade, which should be the same as the direction of rotation of the power tool. Now, while holding down the spindle lock, rotate the disc. It will eventually click in and jam the blade.

Now loosen the clamping nut with the wrench and remove the blade. After inserting a new disc, repeat all steps in reverse order. Make sure the drive is secure before plugging in and getting started. Also, check that the disc can move freely and does not catch on the spindle lock.

Toolless assembly

This is a more convenient method of changing the drive that does not require the use of a wrench or other tools. This is useful if you have to change or replace the drive several times per day.

For this, a special quick-release nut is used. Please keep in mind that this quick-release nut is only for cutting and grinding wheels.

The procedure for replacing the disc and mounting it with a self-locking nut differs slightly from that of using a double pin wrench.

First and foremost, ensure that the marked side of the quick-release nut points outwards (not towards the appliance!). To loosen the nut, grip it firmly with your fingers and turn it counterclockwise while the disc is held in place with the spindle lock. To tighten the nut, follow the procedure in the opposite direction as described.


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