A disk grinder is a tool used primarily for removing stock from a metal workpiece with a rotating abrasive disk. Portable, hand-held disk grinders are commonly found in auto repair shops and home workshops, as well as in industrial settings. Bench-mounted disk grinders are available for home shops, and larger floor model disk grinders and double disk grinders are part of a group of machines called surface grinding machines.
A portable disk grinder, also called an angle grinder, uses an abrasive disk generally no larger than seven inches (17.78 cm), although some can accommodate disks of up to 12 inches (30.38 cm). Many different types of disks are manufactured for disk grinders, making them extremely versatile. The same tool can be used for grinding, cutting, and polishing, making the tool useful not only in shop and industrial applications, but for rescue work as well. Another application for hand-held disk grinders is metal sculpture; most artists who make large metal sculptures routinely employ disk grinders.
One of the most popular applications for a portable disk grinder is smoothing out welds. When two pieces of metal are welded together, the joint is characterized by a raised and uneven section of dried molten metal, which must be smoothed over for aesthetic reasons. The operator presses the face of rotating disk against the metal surface and it grinds away excess metal and smooths it in the same way a disk sander operates. A welded joint that's been smoothed with a disk grinder is often painted.
A portable disk grinder can be used as a cutting tool when a cutoff disk is attached. These are relatively thin, very hard abrasive disks, often with diamond chips incorporated into the design. When a cut off disk is used, the edge of the disk, not the face, is pressed into the workpiece. When used for cutting, a disk grinder can quickly slice through sheet metal, hence its utility in rescue work.
Stationery, bench mounted disk grinders are manufactured for home shops and small industrial applications. A bench-mounted disk grinder is generally configured to accept a grinding or sanding disk up to 12 inches (30.48 cm). This disk rotates vertically, perpendicular to the floor, and the workpiece is pressed against the spinning disk. These tools aren't commonly found in home shops, though, because they're too specialized, and in most cases other tools can as easily do the work.
Disk grinders are also available in large, heavy freestanding designs for grinding and polishing larger workpieces, as well as for grinding and polishing tools and other metal parts. The workpieces are secured in a workholding device called a chuck, which secures workpieces either magnetically or by use of a vacuum, and feeds them into the grinding area. Another freestanding form is the double disk grinder, is capable of extremely high-tolerance work, employing twin grinding surfaces to grind opposite surfaces of a workpiece. Double disk grinders are used extensively in the production of automobile parts.