Grinding is a type of machining using an abrasive wheel as the cutting tool. Grinding is considered to be the most accurate (Marinescu 2006) of the existing machining processes.

 

A wide variety of machines are used for grinding. They include:

 

hand-cranked knife-sharpening stones; handheld power tools such as angle grinders and die grinders; various kinds of expensive industrial machine tools called grinding machines; and the bench grinders often found in residential garages and basements.

 

Grinding practice is a large and diverse area of manufacturing and toolmaking. It can produce very fine finishes and very accurate dimensions; yet in mass production contexts it can also rough out large volumes of metal quite rapidly. It is usually better suited to the machining of very hard materials than is "regular" machining (that is, cutting larger chips with cutting tools such as tool bits or milling cutters), and until recent decades it was the only practical way to machine such materials as hardened steels. Compared to "regular" machining, it is usually better suited to taking very shallow cuts, such as reducing a shaft's diameter by half a thou.

 

Technically, grinding is a subset of cutting, as grinding is a true metalcutting process. Each grain of abrasive functions as a microscopic single-point cutting edge (although of high negative rake angle), and shears a tiny chip that is analogous to what would conventionally be called a "cut" chip (turning, milling, drilling, tapping, etc.). However, among people who work in the machining fields, the term cutting is often understood to refer to the macroscopic cutting operations, and grinding is often mentally categorized as a "separate" process. This is why the terms are usually used in contradistinction in shop-floor practice, even though technically grinding is a subset of cutting.

 

Similar abrasive cutting processes are lapping and sanding.

 

Types of grinding processes

 

Selecting which of the following grinding operations to be used is determined by the size, shape, features and desired production rate.

 

Surface grinding is most common of the grinding operations. A rotating wheel is used in the grinding of flat surfaces. Types of surface grinding are vertical spindle and rotary tables.

 

Cylindrical grinding is also called center-type grinding and is used in the removing the cylindrical surfaces and shoulders of the workpiece. Both the tool and the workpiece are rotated by separate motors and at different speeds. The axes of rotation tool can be adjusted to produce a variety of shapes.

 

Internal grinding is used to grind the inside diameter of the workpiece. Tapered holes can be ground with the use of internal grinders that can swivel on the horizontal.

 

Centerless grinding is when the workpiece is supported by a blade instead of by centers or chucks. Two wheels are used. The larger one is used to grind the surface of the workpiece and the smaller wheel is used to regulate the axial movement of the workpiece. Types of centerless grinding include through-feed grinding, in-feed/plunge grinding, and internal centerless grinding.

 

Creep-feed grinding is used for high rates of material removal. Depths of cut of up to 6 mm (0.25) inches are used along with low workpiece speed. Surfaces with a softer-grade resin bond are used to keep workpiece temperature low and an improved surface finish. up to 1.6 microns Rmax Pre-grinding is when a new tool has been built and has been heat-treated then to be pre-ground before anymore welding or hardfacing commences, this usually involves grinding the OD slightly higher than the finish grind OD to ensure of the correct Finnish size.