Grinders are used to grind, shape, sharpen, finish, and cut any number of materials, even your other Workshop Power Equipment! You might think your workshop is fine without a grinder, but if you're using any kind of tools that require sharpening high-speed or hardened steel, you're going to want a grinder to do the job. If you're a woodworker, gardener or boilermaker, grinders are the right tool for sharpening blades, rounding edges, polishing metal surfaces to mirror-like quality and filing out cylinders and ports.
Essentially your basic bench grinder is an induction motor with abrasive wheels mounted at 90-degree angles at the ends of the motor shaft. These are not made for precision work; they're designed more for preliminary shaping and require a careful touch and coordinated eye. A good grinder should be solid with fully adjustable tool rests and smooth running, quiet motor with enough power to drive both wheels.
* Most home and small-shop bench grinders will use 6"-8" wheels.
** 6-inch grinders should be fine for most household applications, and a smaller diameter wheel can let you make deeper hollow grinds.
* Usually have two gray aluminum-oxide wheels: a coarse 36-grit wheel and a finer 60-grit wheel.
** '''Coarse''': for shaping and fast stock removal.
** '''Fine''': for smoothing surfaces and touching up edges.
* Some grinders feature white wheels, which are made with a special grit adhesive that allows the wheel to shed grit and renew its edge while in use.
** Don't last as long as gray wheels, but run cooler and resist clogging better, thereby reducing the chance of overheating.
* Popular Mechanics favors the Dewalt DW756 bench grinder with its quiet and powerful 4-amp motor, and solid construction.
These grinders are handheld, portable power tools that are good for projects that are too big or cumbersome to fit on the bench. They're also known as '''straight grinders'''. The grinding surface is positioned 90-degrees to the motor. Angle grinders usually come in 4-inch and 9-inch versions.
* Look for power: greater wattage equals more power, which is important since there's a tendency to lean in on them while in use. This stresses the motor even more than usual.
** Look for a 600 watt minimum for small household angle grinders and 1800 watts for a large grinder.
* '''No-Load Speed''': This is generally a non-issue, since almost all work will be done under load.
** More important is how reliably the grinder can maintain its speed while under load.
** Look for '''RPM rating''': this should be greater than or equal to the grinder's maximum no-load speed.
* All grinders should have a multi-position side handle -- consider ones that work for both left and right-hand use.
* '''Safety Gear''': unlike bench grinders, angle grinders don't come with spark deflectors or eye shields. You'll want to have goggles, hearing protection and possibly even flame resistant gloves.
* For a nice side-by-side comparison chart of angle grinders, click here.
These grinders are more specialized than the other types of grinders. They're also handheld and portable, but use a long spindle to reach the insides of cylinders or ports. They're most common in machine and metal-working operations to port and polish the insides of piping, plumbing systems and joints.