A new angle on angle grinders

The M18 Fuel 18V cordless angle grinder from Milwaukee has a brake for added safety that stops wheels and accessories in less than two seconds.

Angle grinders are a very useful and inexpensive choice for chopping off seized bolts, cutting chain or padlocks, cutting bricks and a host of other tasks that are otherwise baffling, awkward and always time-consuming when done another way.

Angle grinders are hand-held and can be powered by air, electric current by wire or – increasingly – by higher-powered battery. When battery-powered, the tool is a little heavy but this is more than made up for by the convenience. And if you already have 18-volt batteries, the cost of the tool is small in comparison to the work it can do.

It’s an angle grinder, or cut-off tool, as it’s sometimes known for its most frequently used mode, because the grinding wheel is on a shaft at right angles to the axis of the motor. Another differentiator of the angle grinder is that it comes with heavy bearings that can contain side loads on the various wheels available, in addition to the axial loads when it’s used as a regular grinder or cut-off tool.

Angle grinders come in a wide range of sizes, though most users will opt for the 4½- to 5-inch grinder because it’s small, light and easily stuffed in a tool bin on a truck or a toolbag on the jobsite.

The RIDGID X4 18V Lithium-ion cordless 41⁄2 inch angle grinder features a tool-less guard design to easily rotate the guard for optimal grinding. A load level LED light protects the grinder by preventing overload. Auto tool lock-off prevents accidental start. If the battery is installed while the tool trigger is locked on, the tool will not operate.

For brick cutting, concrete smoothing and more general work a 7-inch grinder may be preferable but it’s more expensive and harder to use for delicate tasks such as cutting curved lines in tile.

The tool will come with a side-mounted handle and most have a grinder head that accommodates the extra gripping point for right- or left-hand use. It may also allow for central mounting of the handle, which can prove useful, especially when using the angle grinder vertically.

Angle grinders come with a guard that encompasses half the wheel. This is important, because the angle driver is among the more dangerous power tools. The guard is adjustable to any position you need and you should ALWAYS have the guard in place when using the tool.

Guards come in different configurations to allow you to use the tool more accurately and some provide dust collection for a cleaner environment. Some accessories are configured such that the guard either cannot be used or it makes no sense to use it. But again, if there is a guard for a particular wheel, it’s there for a reason.

Because it’s dangerous and noisy, there are a bunch of personal safety items you should wear and use. For one, never even think of switching the grinder on without putting on safety glasses − a full face shield is an even better idea. Heavy gloves, ear protection and, depending on how much dust you’re generating, respirators and dust masks are also recommended.

The reason for all this caution is that one of the major uses of the angle grinder is with a cut-off wheel. This is a 1/16-inch-thick wheel pressed as a composite cutting wheel and bonded together.

The Ryobi 18V One+ 41⁄2 inch angle grinder offers cordless convenience and a speed of 6500 rpm for fast, precise work. Features include onboard wrench storage, a comfortable overmolded grip and a three-position side handle to help reduce fatigue. The tool-free guard allows quick repositioning.

There are many opportunities to misuse the tool, to drop a cutting wheel on the floor, to get it wet and so on that compromise the strength of the bonding of the slim wheel. When it flies apart, extremely fast-flying, sharp and dangerous pieces of wheel slice through the air and anything they come into contact with. There are myriad stories of people being seriously injured by burst cutting wheels.

Never operate an angle grinder without the guard so you can use a larger wheel to get a greater depth of cut. This is a huge no-no. For one, you shouldn’t operate without the guard in the first place, but using a larger wheel places additional centripetal stress on the wheel, meaning it’s more likely to fly apart anyway.

Angle grinder wheels

Angle grinders are extremely simple. It’s the various grinding, cutting and sanding wheels that make it ideal for so many tasks. And grinders are available in different amperage ratings and spindle speeds. Generally, the higher the better.

The on-off switch may have a lock but in the opinion of many tool experts, an angle grinder should never be used with the switch locked on especially when using composite grinding wheels. It’s just too dangerous if things start to go wrong. Similarly, a brake for the wheel once the trigger is released is a nice feature. That being said, it may be okay to lock the trigger and even use the tool without the guard if you’re using it for sanding.

The new Makita XAG03M features Automatic Speed Change technology engineered to adjust speed and torque during grinding or cutting applications for top performance, even under heavy load. In addition, the efficient brushless motor is electronically controlled to optimize battery energy use for up to 50 percent longer run time per charge.

When the angle grinder is switched off, let the wheel come to rest before setting it down. Set it down on its back so there is less chance of banging the wheel on the bench or floor, and potentially cracking it with disastrous results.

Most angle grinders come with a cutoff wheel and a grinding wheel. But there are many different wheels that can be attached to the spindle of the grinder. How they attach varies, as does the flange nut that clamps the disc to the spindle.

For thinner cutoff or other wheels ⅛ inch or less, the wheel is located by the inner flange and the flange nut is used with its flat face toward the disc. For thicker wheels – or according to the manufacturer’s instructions – the nut is reversed so the nut’s pilot flange goes into the disc center.

Never change a wheel with the angle grinder plugged in, and if it’s cordless, remove the battery. Never store the grinder with a composite wheel installed. It’s just too easy to damage the brittle wheels.

The grinder should have a lock button on the housing. Use this and the two-pronged spanner to tighten the flange nut. You don’t need to over-tighten, but snug it up. Some wheels come assembled with their own threaded center. These are mounted to the spindle and locked using the palm of the hand to snug up the wheel.

Blades, discs and wheels are often marked with a direction of rotation. There will be an arrow on the angle grinder to indicate the direction the spindle will turn. Obviously, look for these and make sure they correspond and are correctly mounted.

There are a host of different wheels for different tasks from the 1/16-inch cutoff wheel or blade, to the regular grinding wheel, to wire cup and regular wire wheels for cleaning surfaces to remove rust.

The wheels may be aluminum oxide for cutting metal; silicone carbide or diamond edge for stone, ceramics and concrete; or cotton-reinforced for working on non-ferrous materials. You can also get a sanding accessory pack.

This wide diversity of wheels is what makes the angle grinder so useful. However, make sure you use the correct accessory for the work piece. It will say on the disc what it can be used on. And while you’ll use the grinder at an angle of 5 to 15 degrees when surface grinding, wood removal or sanding, never put any side load on a thin cutoff disc. This is a sure-fire way to have a wheel disintegrate.

If you’re using any type of wire brush on the angle grinder, make sure that all other workers in the vicinity are wearing eye protection as the wires will be coming off the tool with considerable force.

Angle grinder accessories

While the popular angle grinder accessories can be found at The Home Depot, there are also some unique blades available, such as one that turns angle grinders into a mini chain saw for fast removal of wood.  According to the manufacturer it can, in a pinch, be used to attack a wooden stump left after felling a tree. It won’t get it done as fast as a stump grinder, of course, but it won’t cost you $300 a stump, either.

Another wheel has large holes so you can see your work through the spinning wheel. These discs are primarily intended for woodworking, but could come in handy on the jobsite, too.

Another woodworking wheel has three cutting edges on the surface to remove material quickly. It could be quite useful when repairing wooden floors or for tasks like trimming a sticking door. Because the cutting edges are on the surface, the smooth edge of the disc can follow a template.

–By Steve Sturgess, stevesturgess.com