How to use an angle grinder | To cut metal & grind concrete

Angle grinders are among the most versatile metal cutting power tools you can own. They can be used to grind, smoothen, and even cut a wider variety of materials like plastic and concrete. Like any tool, you can get the best results from your angle grinder by knowing what you are doing and following the fundamentals of proper use.

Using angle grinders properly will prevent damage to your tools and workpieces and prevent injury.

Some of the more important factors to consider when working with angle grinders are:

• Kickback. This is when the grinding or cutting wheel gets caught in the material, causing the tool to jerk back or fly out of your hands. Managing kickback is essential for avoiding injury and damage to the tool or your workpiece.
• Safety glasses. Use the required personal protective equipment (PPE) when working with angle grinders, but safety glasses are possibly the most important. These will protect your eyes from flying debris like sparks and concrete dust.
• Using the right tool for the job. Choosing the right sized grinder and the proper cutting or grinding wheel will help ensure good results and prevent injury.
• Sparks. Sparks are a part of the grinding process and are often unavoidable. Knowing the risks that sparks pose and how to deal with them will ensure a safer and more productive experience when using a grinder.

Setting up an angle grinder

Setting up an angle grinder is pretty straightforward, but you do have to keep some basics in mind. The first and most important factor to consider is the work area. You need to assess the potential risk of your workspace to ensure that any possible hazards are minimized. 

Clear out anything that could be slipped on or trip over. Make sure that there are no flammable materials nearby and have adequate ventilation. This reduces the risk of fire caused by sparks and breathing in harmful vapors. 

Secure the workpiece at about waist height or below and make sure that it is supported properly with your foot or a small metal clamp . This reduces the chances of you or the grinder slipping. 

Always use the right-sized disc according to the grinder’s specifications and the task at hand. Pairing an excessively large disc with a small, powerful grinder will increase the likelihood of shattering the disc. Larger discs will also have a larger hole that will fit loosely on the spindle flange, which could cause it to go out of alignment. 

While you’re at it, make sure that the disc is in good shape and isn’t too small or worn out from use. And check the condition of the handle, the guard, and the power cord before starting.

How to Cut Steel with a grinder

Angle grinders are quick and efficient for cutting steel if you have the right cutting disc to match with your tool. Although there are a few options and other tools that can cut metal.

With a powerful grinder and a good cut-off metal-cutting disc, you can cut through sheet metal, iron bars, and even steel bolts.

When to cut metal with a cordless angle grinder

Traditionally, cutting steel meant that you had to use a corded grinder, as most cordless models were too underpowered to do the job efficiently. Nowadays, however, many cordless grinders can cut steel very effectively, with a performance that rivals even corded models. 

There are many advantages to going for a cordless grinder instead of a corded model. You can use them pretty much anywhere, even in remote worksites or areas of your property where there is no power outlet handy. If you have to work outside to avoid disturbing the rest of the household, a cordless grinder is a convenient solution. 

Cordless tools don’t have power leads that can get in your way while working or that may stray onto the path of the cutting blade. This makes them a lot safer than corded grinders, especially if you don’t have a lot of experience working with power tools.

Most cordless angle grinders are smaller and lighter than their corded counterparts. They will fit neatly into a tool bag so you can carry them to remote locations and work in tight spaces. Of course, you do need to make sure they are carrying a full charge and have a spare battery handy.

When to cut metal with a corded angle grinder

As impressive as newer cordless grinders can be, many pros and even DIYers still swear by a corded model. In terms of power and performance, many mid-range corded grinders still out deliver cordless grinders.

If you have to do a lot of heavy-duty cutting and grinding and you need a lot of power for the job, few cordless grinders are as capable and as reliable as a corded model.

And even if you find a cordless that can deliver comparable performance and capabilities, you will probably end up paying a lot more than if you had just opted for a mid-priced corded grinder. 

Of course, all this power comes with some caveats. Operating a corded grinder requires more care and precaution than using a cordless grinder, simply because they are so powerful.

You also need to have a power outlet nearby and make sure that the cord doesn’t get in the way of the cutting blade. 

On the other hand, going corded means that you never have to worry about batteries running out of juice. And if you have to cut through several sheets of steel, you can pretty much work with a Dewalt corded grinder for hours at a time without having to stop to charge your grinder’s battery. 

When to use a chop saw instead

For cutting steel, you could use a chop saw instead of an angle grinder. Also known as cut-off or abrasive saw, chop saws have stationary bases and abrasive cutting discs called cutoff wheels. These wheels are attached to hinged arms that swing downward to make cuts in the material. 

The cutoff wheels in chop saws take the place of the saw blades typically used in other cutting tools.

That being said, there are cold-cut chop saws that can be effective for cutting steel. Instead of the abrasive discs used in standard chop saws, cold-cut saws have metal blades with tungsten carbide tips.

These saws prevent excessive heat build-up on the blade and the workpiece. They also produce fewer sparks and dust during cutting and reduce discoloration of the workpiece’s surface. 

There are also industrial-sized chop saws that are even larger and more powerful than standard chop saws. These have large bases that extend off the ground, and heavy casters that reduce vibration.

Industrial chop saws are pretty powerful, and most DIYers probably won’t have much use for them unless they frequently have to cut large sheets of steel.

Find out more about metal cutting chop saws here. 

How to cut concrete

Grinders are actually quite effective at cutting concrete, provided you have enough speed and power, and you use the right cutting disc, preferably one with a diamond blade.

Although there are tools that are better suited for heavy-duty concrete cutting work, a good angle grinder can be very useful for small to medium tasks.

1. With a 9-inch angle grinder

Although 9-inch grinders may seem like a good choice for cutting concrete, they are often too big and heavy for most uses. They also tend to vibrate a lot, which could be very difficult and even unmanageable for those that don’t have a lot of experience with angle grinders.

In some cases, the vibrations produced by 9-inch grinders can even loosen the screws from the grinder, if it’s not a good brand, and can leave your arms numb after use. 

If you have to cut concrete or do a heavy amount of grinding, however, a 9 Inch grinder is a lot faster and more suitable for the job compared to a smaller handheld grinder.

2. Using a 4.5-inch angle grinder

Many 4.5-inch grinders are quite effective for cutting concrete. Some professionals actually prefer using 4.5 or 5-inch grinders instead of a 9-inch model for small concrete cutting work, pairing the tool with a suitable cutting disc. In particular, “Super-Turbo” discs can cut concrete very efficiently, greatly adding to the versatility of a smaller grinder. 

Of course, the same theory applies when you need to make large cuts into huge concrete slabs. A semi-stationary cut-off machine would be better suited to heavy-duty work. But if you only work with smaller concrete pieces, a good 4.5 or 5-inch grinder paired with the right cutting disc will do just fine if it can reach the depth.

3. With a concrete cutting saw instead

If you need to cut a lot of concrete, you might want to consider getting a concrete cutting saw for your workshop. These saws have blades specially designed for cutting concrete, which may be made of corundum or some other metal fitted with a diamond edge. 

Corundum blades are much cheaper than diamond-tipped blades, but they wear out pretty quickly and are only useful for ¼” to ½” cuts and. They’ll get the job done, but be prepared to put in a lot of work and change blades frequently. Diamond-tipped blades are pretty expensive, but they will last a lot longer than most abrasive blades.

How to grind concrete

When using a grinder to smoothen out concrete, consider factors such as the speed and power of the tool, as well as the floor space you need to cover. In general, you will want to use a grinder that is capable of high speeds when working on concrete.

1. 9-inch angle grinder with a cup stone

A  9-inch angle grinder with a cup stone attachment will do nicely for grinding concrete and leveling bumps in concrete floors. If you don’t have to grind too deeply or if you are simply smoothing, you could even use a sanding disc or a coarse buffing pad. 

Don’t try to take off too much concrete at once. Keep in mind that a 9-inch disc can take off a lot of material quickly, so go slowly if you don’t want to risk damaging your floor from over grinding. If it’s your first time grinding concrete, try practicing on a high spot first.

2. 4.5-Inch Angle Grinder With A Cup Stone

If you only need to remove small bumps in the concrete or smoothen out a rough edge, a 4.5-inch grinder might be a better choice than a 9-inch model. These will remove a smaller amount of material at a time, so there is less risk of damaging the concrete.

You will also find it much easier to control a 4.5-inch grinder, so it is possible to get pretty good results even if you don’t have a lot of experience using a grinder.

3. A dedicated floor grinder

If you need to do a lot of refinishing work on a floor, you might be better off using a dedicated floor grinder instead. These tools will grind concrete much more quickly than by hand. A floor grinder is much easier to use as well to get an even level finish over large concrete areas compared to by hand.

Floor grinders can also be used to roughen up concrete surfaces for aesthetic design purposes, and are a much quicker alternative to angle grinders if you have to cover a large floor area.

How to grind steel

Grinders can be used to restore the edge of dulled blades and even reshape worn tools. You can use either bench grinders or angle grinders, depending on the tools you need to work on, and how you want to work.

1. With a handheld angle grinder

 Hand-held angle grinders are often better options for sharpening or grinding larger tools that would be awkward or difficult to hold against a bench grinder. In this case, the tool or workpiece remains stationary while you apply the grinding disc to the edge.

This will give a lot more control over the grinding motion, allowing you to shape and sharpen tools more precisely like shovels and axes.

2. Using a benchtop grinder

Conversely, for sharpening handheld tools, the best variable speed bench grinder might be a better option than a handheld angle grinder. Instead of applying the grinding disc to the workpiece as you would with an angle grinder, bench grinders remain stationary while you press the workpiece to the grinding disc. These workpieces may be blades or tools with edges that you need to sharpen.

You can also use bench grinders to smoothen out burrs in metal or to reshape tools like your fiskars axe when it has become worn from repeated use.

What PPE to wear when using a grinder?

Apart from safe practices and common sense, one of the best ways to ensure the safe operation of an angle grinder is to use personal protective equipment (PPE). These come in many forms, each intended to protect a specific body part or area of your body. The PPEs you should use are:

• Safety goggles or a face shield.
• A dust mask.
• Earplugs or earmuffs (preferably both).
• Cut-resistant leather gloves.
• Flame-resistant clothing.
• Safety boots.

These pieces of equipment will provide the best protection from sparks, debris, fine particles, and sharp materials.

Make sure the safety glasses seal to your face like the blue or green pair, otherwise sparks can bounce into your eye.

Do sparks from a grinder hurt

When using an angle grinder to grind, smoothen, or cut metal, you are probably going to have a good amount of sparks flying out. Make no mistake: those sparks are very hot because they are, after all, made of heated metal dust. But the thing about those metal particles is they don’t have a lot of mass. They will, therefore, burn out pretty quickly, so they aren’t likely to burn you.

Of course, a larger particle might sting a bit, so you generally want to keep clear of the sparks or wear protective clothing. In most cases, however, you don’t have to worry about the occasional sparks coming your way, they won’t hurt or do any damage if they hit your skin, but definitely never let a spark anywhere near your eyes, as a hot spark can embed.

How to safely use angle grinders

Don’t be fooled by the relative simplicity of angle grinders. These are serious tools for serious users, and they will hurt if you aren’t careful. That said, you can use angle grinders safely, provided you keep a few simple tips in mind.

1. Get the set-up and positioning right

Make sure that your work area is clean and free of obstructions. You want to be able to move freely without anything getting in your way or anything coming into contact with the grinding or cutting wheel. 

Keep the grinder below waist height, cutting and grinding with your work on the ground is the safest. If the tool was to catch and kick back, the lower the tool is the easier it is to control, and the further away it is from vital organs, making the job pretty safe with a firm hand.

A good way to position metal for cutting is to use your foot with leather steel cap boots to put weight on the metal rods you are cutting, with a block of wood underneath while keeping 2 hands on the tool.

The best way would be to use heavy duty c clamps to hold your workpieces sturdy so you can have the best foot balance. While having 2 hands firmly on your angle grinder.

2. Understand the dangers of kickback

Kickback is a major concern when working with all bladed power tools.  Kickback is when a blade or
wheel gets jammed up while cutting, causing the tool to suddenly kickback, this can cause the operator to lose control of the tool if not prepared for it.

If this happens, the angle grinder can jerk away from the workpiece towards you or fly out of your hands. In either scenario, there is a risk of damaging your workpiece or causing injury to you or people nearby. 

Avoid kickback by using the right-sized tool and wheel on a grinder. You should also keep a firm grip on the tool with both hands and ease it to the workpiece you are cutting slowly.

Most importantly kickback is caused by the material you are cutting folding and jamming on the blade. To stop this always allows one piece to fall away freely when you are cutting metal. When cutting concrete kickback generally occurs because the blade has started to twist inside the channel you are cutting, make sure to keep the blade inline and straight when cutting deep concrete cuts and never let the tool struggle.

When an angle grinder tool starts to struggle this is a warning of pre-kickback, there is some resistance on the blade properly because you might be twisting the blade of the tool in the cut. If you notice a tool struggling immediately release the trigger and remove the grinder from the cut, start the motor up again, and re-enter the cut nice and slowly making sure to keep the blade straight.

Refer to my guide on how to use a circular saw for beginners for more tips on how to avoid kickback when using a grinder as it is the same with a circular saw.

3. Wear quality eye protection

Eye protection is a must when using an angle grinder. These tools can produce sparks and debris, any of which can enter your eyes. Make sure to wear high-impact-rated wraparound goggles or, better yet, a full face shield.

4. Wear hearing protection

Don’t neglect protection for your ears. Angle grinders make a lot of noise, especially if you are working with steel or concrete. Earplugs will do in a pinch, but it would be best to go for reusable earplugs rather than disposable ones.

For maximum protection, use professional ear caps or ear muffs that block out noise more effectively.

5. Take lung protection measures

Finally, it’s important to wear a dust mask to prevent breathing in fine particles like concrete dust. Make sure that your dust mask provides a snug fit without hampering your breathing.

Conclusion

A Cordless Angle Grinder is a quick portable way to cut metal, A corded  9-Inch Grinder is best for grinding and cutting concrete, and a bench grinder is best for grinding jobs that require accuracy. You can do all jobs pretty much with a corded Hand-held angle grinder.

If you have never used an angle grinder before it can be intimidating because of the sparks, but it really isn’t that hard to use, and its a relatively safe if use, especially if you are using a cordless cutoff tool following you take the right precautions.