Grinders are versatile tools designed for cutting and shaping very hard materials, including metal and masonry.
At first glance, common grinder types seem to vary radically. But if you look closely, they're all built similarly: a motor and a shaft upon which a grinding wheel or other accessories are mounted.
Bench grinders are typically the largest tool in the group
. They're meant to be screwed or bolted to a workbench or work stand before use. Because they're stationary, they're ideal for sharpening everything from garden spades and shears to chisels and drill bits. You can also use them to dress up the blade of a worn screwdriver. With accessory wheels they can be used for other tasks, including rust removal and polishing.
Angle grinders are more specialized.
They allow you to bring aggressive grinding and cutting action to where you need it. If you're into welding, it's your busiest tool, as it's needed for cutting metal, cleaning up welds, and deburring. In addition, angle grinders can be used to shape and cut masonry, including brick, cement block, ceramic tile, and stone. While they can also be used for heavy-duty carving and sanding of wood.
Die grinders, sometimes called rotary tools, are small cylindrically shaped, hand-held grinders.
Juergen Effner, Corbis
They can be electric or pneumatic, light- or heavy-duty. The shaft is fitted with a chuck that can accept a multitude of small grinding wheels, grinding drums and cones, circular blades, and drill bits. Fitted with a cone-shaped grinding bit, you can quickly and easily deburr the inside of a pipe. Other accessories allow you to shape metal, wood and plastic, and to do engraving. Die grinders are a specialty tool, primarily useful to metal workers and to hobbyists, such as model makers.
Operation varies for each type of tool. With bench models, you can grind or sharpen with either the rim or the face of the grinding wheel. A tool rest gives you a steady surface upon which to rest small items, such as knifes, drill bits, and chisels, while you sharpen them. Angle grinders are easy to use. Just grasp it firmly with both hands and touch the wheel to anything you want to shape or cut. Die grinders are also easy to use and are meant for one-handed operation.
Homeowner-grade bench grinders come with 6" or 8"-diameter wheel sizes. The two-wheel, 6-in. models are fine for most homeowners. Be sure the model you choose comes with substantial, easy-to-adjust tool rests. A built-in work light is handy as well. A variable speed motor will add to the cost, but is probably worth it if you do a lot of sharpening. Being able to hone fine edges at lower speeds helps prevent overheating the metal and ruining the edge. As far as accessories go, you'll want two grinding wheels, one coarse for aggressive removal of material and one fine, for sharpening. The tool should also come with a wire wheel for rust removal and a polishing bonnet.
Hold off on buying an angle or die grinder until you have a task that demands one. When buying the former, opt for one with a 4.5-in. dia. wheel for general use as they're lighter in weight. Spend a little extra and buy from a top manufacturer as these tools you will eventually ask this tool do some tough work. DeWalt and Bosch make excellent low-vibration models with high-amp motors and convenient features, such as no-tool wheel changes and a key-less adjustable guard.
Bench grinders: $40 to $90
Angle grinders: $50 to $180
Die grinders: $50 to $350
Clean clogged abrasive grinding wheels with a dressing tool. A clean wheel will sharpen faster, with less heat. Blast grit from the tool with compressed air after each use. Change motor brushes per the manufacturer's recommendation.
Eye and hearing protection are essential when using bench and angle grinders. Respiratory protection is also advised when grinding materials the release dust or fumes. Wear gloves when using an angle grinder to counter vibration, but not when using a bench grinder. With some models it's possible for a gloved hand to be pulled between the wheel and tool rest.
The major caution for these tools have to do with the grinding wheels themselves. They must be securely fastened to the grinder shaft per the manufacturers directions-but not be overly tightened. In use, do not stress a grinding wheel by applying too much pressure and causing the wheel to heat up or by bumping it with the work piece. Wheels are breakable, and can shatter and throw off fragments at high speeds. Never use a grinding wheel that has been chipped or that shows signs of fractures. Review the manufacturer's safety guidelines for your grinder and grinding wheels carefully before mounting the wheel and operating the equipment.