Angle Grinder for Welding

For the modern metalworker, an angle grinder is one of the most essential tools of the trade. Welding is discussed so much more regularly that the Angle Grinder is often forgotten while in reality, most welding procedures would not be as straightforward or aesthetical without its assistance.

In this article, we are going to remind metalworking beginners and pros alike just how useful the angle grinder is for welding.

What Is an Angle Grinder Used for in Welding?

If you’re a welder, chances are you have a few angle grinders lying around. There’s a good reason for that: angle grinders are extremely versatile tools. They can be used to cut, shape, weld, and polish metal.

Here are some of the common ways an angle grinder is used in welding.

1. To Cut Metal

One of the most useful applications for the angle grinder in welding is for the cutting of steel to size.

Angle grinders are produced in sizes ranging from 4.5 inches (115mm) to a whopping 9 inches (230mm). This allows the machine to cut a variety of metals at different thicknesses. There is no minimum thickness at which a large angle grinder can cut; however, 3 ½ inches is the maximum depth of cut for a 9 ″ angle grinder.

An angle grinder with the right cutting disc allows a welder to trim steel down to the required length, width and thickness, and shape, something which is highly essential to the welding/fabrication process.

 View our guide on Cutting Steel with Angle Grinders if you are interested in more detailed information surrounding the topic.

2. Preparing the Base Metal

Often with welding preparations, it is a requirement to remove material from the base metal (surface of the metal) before welding commences. We do this because the surface of the metal can have nasty contaminants such as paint, rust, plastic, soot, and chemical treatments which can affect the weldability of the metal.

You can improve the weldability of your metal joint by cleaning it with an angle grinder and a flap disc. Usually, a flap disc with a grade coarser than an 80 grit is not necessary, as all that you need to do is lightly sand the metal surface to remove these contaminants and to reveal the pure steel beneath.

Imagine sanding 1meter or more long material manually with sandpaper and a wire brush. An angle grinder will always be more practical here.

3. Preparing Welding Joints

A uniformed and consistent joint shape is essential to the welding process. A joint with an inconsistent edge will produce an equally inconsistent weld.  An angle grinder with a grinding disk or flap wheel (coarse grit) is commonly utilized for its efficiency in these preparations.

Grinding discs and flap wheels are used as they are flat, easy to control, and consistent in speed, and with a little skill and practice, joint preparation is easy. The operator needs to adjust the flat face of the disc to the required angle (depending on the type of flap discs) and run the disc horizontally along the edge of the material in a back and forth motion.

4. Finishing the Weld

To add to the growing list, angle grinders are excellent tools for weld finishing and tidying up.

Stick and MIG welding by nature produces splatter (molten metal spots which stick to the area around the weld. Spatter can be removed with a hammer and chisel or wire brush but usually not all of it. This is where the angle grinder comes into play once again; you should use a fine-grit flap wheel to lightly remove all splatter with speed and tidiness.

Welds will often have very minor but noticeable deformities such as the start and stop location of the joint. Here the weld will look slightly more raised than the rest of the bead and it is necessary, for aesthetic purposes, to remove this raised bump. A grinding disc is used to sand away this proud spot and the result: a weld bead looking much more uniform. 

5. Removing the Weld

Welds are generally removed when there is an error with the design, the quality of the weld is low, you are repairing an old project, or it could be for aesthetic purposes.

There are two methods to remove and repair a weld and they both require the assistance of an angle grinder.

1. You use a sanding disc to remove the top of a weld and make it flush with the material, then you would use a grinding disk to make a groove into the flattened weld. Into this groove, you can reweld the joint once more. We would generally use this method for minor repairs of low-quality welds.
2. You cut through the weld completely with a cutting wheel, then you prepare the joint once more to the requirements of the job, tack it back together, and reweld it once more. This method is more commonly used as it guarantees a strong new weld.

When removing welds for aesthetic purposes, processes to be used will vary depending on the situation.

Despite this, a sanding disc is nearly always used as the first step to make the weld flush with the surrounding material, from here one would select the finishing process more suitable to the project at hand. For example, if the objective is to create a piece of steel that looks like it has never been welded, one would use very fine-grit sanding discs to achieve this.

Best Angle Grinder for Welding

The choice of the best angle grinder for welders depends on the task (cutting or grinding) and the work location (outdoor or indoor). A cordless angle grinder is very convenient when working on outdoor construction sites, while a corded version offers more power and is ideal for garages and workshops.

What Size Angle Grinder for Welding?

You need a 6 ″ grinder or larger for cutting metal rods, beams, angle irons, round and square bars, etc. The compact 4 ½ ″ is recommended for most other welding-related tasks including prepping, cutting notches, grinding weld beads, and finishing.