Angle Grinder to Cut Metal (How to Guide)

Cutting metal is an important part of metalworking. Without the ability to slice your steel into two most projects would simply not even begin let alone exist. In this article, we are going to discuss a popular and useful metal cutting tool, the Angle Grinder, and some basic steps and tips on how to utilize this useful tool efficiently.

Can You Use an Angle Grinder to Cut Metal?

You can cut both soft and hard metals with an angle grinder by using abrasive cut-off discs. You will need different types of cutting wheels for ferrous (steel) and nonferrous metals (aluminum, copper, brass, etc.). Due to its handheld design and disc size, angle grinders are usually limited to a maximum of 2 ¾ inches (70mm) deep cuts.

The above image shows an angle grinder cutting a large diameter, welded steel pipe.

Caution Do not use the metal cutting circular saw blades on angle grinders. Those blades are designed to work with power saws with base-shoe where the work will be pulled towards the base during cutting.

Selecting the Right Cutting Discs

With different types of discs available, it can be difficult to select the right cutting disc for the right job. To simplify the process, keep in mind the following.

What you need for cutting metal is the abrasive cut-off disc (also called  cut-off wheel).

However, you can also get all-purpose metal cutting wheels that can penetrate through a wide variety of metals. While they do not perform as efficiently as a dedicated disc, they are very versatile.

A General Purpose Cutting Disc from Dewalt – Click Here to Buy

What type of metal are you going to cut?

Cutting discs contain different abrasives which allow the disc to actually be able to cut steel but also, different abrasives are designed for specific metals. Take care with this step as if you select a disc designed for another metal, you could completely destroy your job by contaminating it.

For instance, you would never use a mild steel cutting disc for stainless steel as you would contaminate the stainless.

What is the material thickness?

The thickness of the material will determine which cutting wheel size to use and which size of angle grinder. A safe bet for most metal cutting jobs however is a 5-6 inch size grinder with a 1-1.6mm cutting wheel. A 9-inch grinder would be used for long deep cuts to be made on thick steel or welds.

How thick does the cut need to be?

It is uncommon to require a disc below 1 mm or over 1.6mm in thickness, as between this size range, most metal cutting jobs are doable.

However, you can use a 0.8mm disc for cutting very thin sheet metal. You should use metal cutting discs with 1.6 mm + thickness for cutting heavier materials. To note, cutting discs with a greater thickness will cut slower and produce excess heat and discoloration on the steel which may not be wanted. So, it’s best to stick to a 1.6 mm disc for most situations on heavy steel projects.

How long do you plan to be cutting for?

There is no practicality in using a 1 mm cutting disc when you have hundreds of cuts to make, it would simply wear away the disc too quickly. A 1.6 mm cutting disc would be more useful as it is long-lasting on repetitive work.  You could also get specially designed long-lasting discs available in the market.

Types of Cutting Discs

Type 1 Cutting Disc (Type 41)

The type 41 cutting disc is an abrasive cut-off wheel with a flat surface. It is usually called a Type 1 Cutting Disc. Technically Type-1 is the straight grinding wheels and type-1a or Type-41 is the cutting disc.

The type 41 discs have a completely flat surface center to the edge which allows for excellent efficiency when in use. This is because the maximum depth of the cut can be utilized from this disc.

One downside to Type 41 discs is that they mount tight against the guard, which minimizes visibility, but it is worth it for the perks. These discs are produced stiff and slightly flexible.

A word of warning, Type 41 discs are prone to exploding when over flexed whilst cutting. Take care of this to avoid injury.

Type 27 Cutting Disc (Type 42)

Also known as Type 27, the Type 42 cutting discs have a depressed or valley-like center. This center allows the locking flange nut to be below the surface of the disc, which proves to be a huge benefit of these discs. Use the type-42 disc with an open-face guard when you want to flash-cut a bolt or cut around corners.

They are safe to use as the grinder nut is unlikely to come loose as it sits snugly in the center space. On the downside type-42 discs are expensive and their cutting ability is limited.

Type 1 vs Type 27 Cut-Off Wheels

The difference between a Type-1 and a Type-27 wheel is that the type-1 has a fully flat surface across the thickness of the wheel whereas a type 27 wheel has a depressed center. Type-1 and Type-27 refer to grinding wheels; for cut-off discs, they used to be Type-1a and Type-27a. Today cut-off discs are denoted as Type-41 and Type-42 respectively.

Grinder Gaurds

You might have noticed that there are two types of angle grinder guards; type-1 and type-27. The main difference here is the depth of the guards. Usually, the type-1 is a closed face guard and the type-27 guard is an open guard allowing you to grind with the face of the type-27 grinding wheels.
It is best to use a closed-face safety guard while using a cut-off disc. I strongly encourage you to read the manual of your angle grinder since different manufacturers have their own safety guard designs.

Cutting Wheel Abrasive Material

When discussing ferrous and non-ferrous metals, the abrasive (or more specifically the grain within the abrasive) of a cutting disc is important to identify. Cutting discs made of Silicon Carbide and Aluminum Oxide abrasives are most commonly used for metal cutting.

Cutting Ferrous Metals

Aluminum Oxide is more suitable for cutting ferrous metals like Mild Steel, Stainless Steel, and Cast Iron.

When working on more specific project grains such as Ceramic alumina and Zirconia alumina can come into play.

Stainless Steel

Ceramic Alumina is excellent for stainless steel as it cools quickly and won’t overheat the material. The temperature generated during cutting is an important factor to consider with stainless steel since it can become heat distorted easily. Zirconia alumina is useful for heavier duty projects as it proves to be a highly durable disc with a long-lasting lifespan.

Non-Ferrous Metals

Silicon Carbide is the preferred grain for cutting non-ferrous metals such as Aluminum, Copper, and Titanium.

As I said earlier, by using the wrong disc for the wrong metal (ferrous disc on non-ferrous metal), your metal could potentially become contaminated. If you use an abrasive wheel designed for hard material to cut a soft material such as wood, the wheel will get loaded. This will affect the cutting ability and the disc could shatter. You can seriously get injured and damage the workpiece.

How to Use an Angle Grinder to Cut Metal?

An angle grinder with a cutting wheel is the most dangerous handheld tool on the market. Without the correct training, knowledge, and care one can seriously hurt themselves or others. Follow our step-by-step guide below on how to set up and use your Angle Grinder safely and efficiently for cutting metal.

1. Select the Right Disc and Angle

Pick the right cutting disc by considering the material to be cut (ferrous or non-ferrous), depth of cut (disc size), and type of cut.

2. Inspect Your Grinder and Cutting Disc for Wear and Age.

The grinder itself does not have to be in perfect condition to work efficiently, they are designed for a hard life. However, check the center nut and thread for serious damage, otherwise, you’re good to go. The cutting disc should be immaculate. Never use broken or corroded cutting discs as you will face the risk of the disc exploding while in use.

3. Fasten Your Cutting Wheel Onto Your Grinder.

If it’s Type 41 Disc (flat) that you are using, the nut should be on the flat side down. When using type 42 Disc (depressed), the protruding part of the nut should be face down and sitting snugly inside the disc.

Don’t over tighten the nut, just tight is fine as it will tighten further and further when in use.

4. Clamp the Workpiece

The workpiece you are cutting must be firmly clamped at one end. Make sure that the cut-off piece can fall off freely, or else it may close onto the cutting disc.

5. Put on Your PPE Gear (Personal Protection Equipment).

At a minimum, you should wear safety glasses and earplugs, but it is recommended a face shield and a leather apron. When working with larger grinders you can use wear leather or sturdy gloves for better grip.

Do not wear loose gloves since they can get caught in the grinder which can cause serious injuries. Do not compromise on safety when working with angle grinders.

6. Switch on the Grinder and Inspect Rotational Motion

Before beginning to cut, watch the disc as it spins to make sure you have fastened it correctly. It should be smooth with its rotation and without any inconsistency.

7. Begin Your Cut

Make sure that what you are cutting has no electrical materials, gas components, or other objects that you do not wish to cut below it. Have the guard of your grinder facing towards your body while holding it with two hands. Your arms should never be crossing over each other while cutting.

8. Cut at 90 Degrees

The cut-off wheel should touch the workpiece at 90°, preferably at the weakest cross-section. If you feed the rotating disc at an angle, any slight lateral force will result in the breakage of the abrasive disc.

9. Let the Blade Do the Cutting

Do not force the cut with excessive pressure or else you will end up with a shattered disc. While it is not necessary to apply a lot of pressure but do not expect the grinder to do all of the work for you.

Watch the material as you cut and do not try to cut too fast. If cutting a long length of metal you can follow two methods to cut your material efficiently.

1. Move the grinder and cutting wheel slowly across the desired cutting length while applying pressure, being careful to be aware that when you move the wheel back in your direction, that it can bite.
2. Start the cut at one end and finish at the other end of the desired line while cutting completely through the section as you go. Choose a method that suits your job and comfort.

10. Finish Your Cut.

As your cut is about to end, this is the moment in which the grinder could most likely kickback from pinching between the metal. Finish your cutting with a slightly lowered amount of pressure applied to prevent this.