One of the most common grinding machines in the average shop is the surface grinder. It is comparable to a multi-toothed milling cutter, except it has a grinding wheel as its abrasive cutting tool. This wheel removes much smaller chips of metal. The deposit of such tiny chips, called swarf, occurs because the grinding wheel is composed of thousands of cutting edges.
Two types of abrasive material are used in the grinding wheel. Aluminum oxide is used when machining materials with a high ductility, or ability to deform permanently. Silicon oxide is used for materials with a low ductility.
The abrasive grains in a grinding wheel allow for a smooth finished product, regardless of the material being worked on. These abrasive particles are usually coated with a diamond dressing. Steel, aluminum, and glass are examples of the many materials that can be ground. The surface grinder is commonly used as a finishing operation.
There are two basic types of surface grinder. Both types grind flat surfaces only. Planer-type grinders keep the grinding wheel stationary while moving the worktable. This reciprocating back-and-forth motion can be controlled manually or by means of a mechanical or hydraulic drive mechanism. The spindle used to rotate the grinding wheel can be vertically or horizontally placed.
A rotary-type grinder has a revolving, circular worktable. The grinding wheel also rotates. Spindle-assisted rotation can be either vertical or horizontal.
There are several reasons for using a surface grinder. The obvious one is for removal of excess material. A surface grinder is good for machining very hard materials such as steel and diamond. It produces a high quality finished surface. Very small tolerances can be maintained.
The surface grinder has evolved over time. Ergonomic and portability concerns have created a market of user-friendly machines. Computer Numerically Controlled (CNC) grinders are available. PC-based control systems make user interface easy.