Angle grinders are one of the few handheld power tools designed primarily for metalworking. However, they’ve since been found to be useful for a variety of other purposes. Replacing the grinding wheel with different mediums allows it to be used tasks ranging from concrete finishing to removing decals from vehicles.
The angle grinder is a fairly simple tool with an electric motor run through a right-angle gearbox. The output of the gearbox then becomes the arbor for attaching the grinding wheel or other medium. By using a right-angle gearbox, the tool becomes much more ergonomic to hold onto, making it both more comfortable to use and much easier to control.
Typically, they’re held two-handed, providing excellent control. The other thing the gearbox does is reduce the chance of the tool binding up from too much of a load being placed on it.
While simple, the angle grinder is a very effective tool. When used for metalworking, it’s used predominantly used for smoothing and grinding welds, removing weld splatter, slag, and excessive weld. The high tool speed and rough grinding medium allows it to work quickly.
A variety of grinding wheels and other attachments can be connected to a grinder, each of which is designed for working with particular materials and performing particular tasks. These include grinding wheels for different materials, metal cutting wheels, wire brushes, polishing bonnets and Scotchbrite pads for cleaning and paint stripping.
Of all the handheld power tools on the market, angle grinders provide the least protection for the user. The guards on these tools are minimal and only cover the back side of the attachment, the side facing the user. It’s typical to produce a large amount of sparks when using a grinder so protective goggles and gloves should be used. It’s also important to ensure the tool has come to a complete stop before setting it down.
Selecting a Grinder Size
While there are several sizes that angle grinders are made in, they basically fall into two categories, small and large. The small ones range from 4” to 5” and the large from 7” to 9”. Smaller grinding disks can always be attached to a grinder, but larger ones can’t. It’s also important to take into consideration the maximum speed of any particular attachment.
Grinders rotate at high speed and the attachment must be able to withstand the rotational force without coming apart. These attachments typically have the max RPM stated on them to provide the user the ability to properly selecting their attachments.
While two angle grinders may have the same rotational speed, that doesn't mean they’ll provide the same amount of cutting action. A larger grinder will be moving faster at the edge, as measured in feet per second than a smaller grinder moving at the same RPM. This makes the larger grinders cut faster, giving them preference for commercial use.
This increase in cutting size means that you should pick the largest grinder that you can reasonably fit within your tool budget. That will ultimately save you time and have the tool pay for itself.
What to Look For in an Angle Grinder
Power
When selecting a grinder, power and size are the two major considerations. The higher power allows you to put more pressure on the grinder, making a bolder cut. While speed and wheel size are important factors in grinding capability, the amount of pressure placed on the point of contact with the workpiece is important as well.
Comfort
Operator comfort is also an important factor when selecting a grinder. Tool weight, adjustable handle positions and over-molded rubber handles all play a part in operator fatigue. While not usually the number one factor when selecting tools, these factors shouldn’t be ignored.
Gear Greasing
When buying inexpensive angle grinders, one of the best things you can do is to open up the gearhead and fill it with grease. The gears themselves will probably be greased, but by adding more grease you will help to cool the gears and allow them to last longer.
Brushes
Of all power tools, angle grinders go through motor brushes faster than any other. This probably has to do with the fact that when these tools are used, they’re typically on for extended periods of time. Ease of brush replacement and availability of replacement brushes are both important factors for cases where the grinder will be used a lot.
Cordless Grinders
Besides the two different size ranges of angle grinders that are available on the market, there are also cordlessgrinders. These are only available in the smaller size range, as the larger grinding wheel requires more power to operate.
Cordless grinders are great if you are working on a remote site, but can be a bit of a hassle in a workshop. Generally speaking, when angle grinders are in use, they are on for an extended period of time. Even though cordless angle grinders use Lithium-Ion batteries, the batteries can only power the grinder for a certain amount of time. If you’re using the grinder continually, you will probably need a total of three batteries and two chargers to keep the unit operating constantly.