Grinding wheels contains

abrasive An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away by friction. While finishing a material often means polishing it to gain a smooth, reflec ...

compounds for

grinding Grind is the cross-sectional shape of a blade. Grind, grinds, or grinding may also refer to: Grinding action * Grinding (abrasive cutting), a method of crafting * Grinding (dance), suggestive club dancing * Grinding (video gaming), repetitive and ...

and

abrasive machining Abrasive machining is a machining process where material is removed from a workpiece using a multitude of small abrasive particles. Common examples include grinding, honing, and polishing. Abrasive processes are usually expensive, but capable of ti ...

operations. Such wheels are also used in

grinding machine A grinding machine, often shortened to grinder, is a power tool (or machine tool) used for grinding. It is a type of machining using an abrasive wheel as the cutting tool. Each grain of abrasive on the wheel's surface cuts a small chip from the ...

s. The wheels are generally made with

composite material A composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or ...

. This consists of coarse-particle aggregate pressed and bonded together by a cementing matrix (called the ''bond'' in grinding wheel terminology) to form a solid, circular shape. Various profiles and cross sections are available depending on the intended usage for the wheel. They may also be made from a solid steel or aluminium disc with particles bonded to the surface. Today most grinding wheels are artificial composites made with artificial aggregates, but the history of grinding wheels began with natural composite

stones In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition, and the way in which it is formed. Rocks form the Earth's o ...

, such as those used for

millstone Millstones or mill stones are stones used in gristmills, for grinding wheat or other grains. They are sometimes referred to as grindstones or grinding stones. Millstones come in pairs: a convex stationary base known as the ''bedstone'' and ...

s. The manufacture of these wheels is a precise and tightly controlled process, due not only to the inherent safety risks of a spinning disc, but also the composition and uniformity required to prevent that disc from exploding due to the high stresses produced on rotation. Grinding wheels are

consumables Consumables (also known as consumable goods, non-durable goods, or soft goods) are goods that are intended to be consumed. People have, for example, always consumed food and water. Consumables are in contrast to durable goods. Disposable produc ...

, although the life span can vary widely depending on the use case, from less than a day to many years. As the wheel cuts, it periodically releases individual grains of abrasive, typically because they grow dull and the increased drag pulls them out of the bond. Fresh grains are exposed in this wear process, which begin the next cycle. The rate of wear in this process is usually very predictable for a given application, and is necessary for good performance.

Characteristics

There are five characteristics of a cutting wheel: abrasive material, grain size, wheel grade, grain spacing, and bond type. They are indicated by codes on the wheel's label.

Abrasive Material

The abrasive aggregate is selected primarily according to the hardness of the material being cut. Chemical compatibility is also a concern. For example because carbon alloys with iron, silicon carbide is not suitable for use with iron-based metals like steel. * Aluminum oxide (A) *

Silicon carbide Silicon carbide (SiC), also known as carborundum (), is a hard chemical compound containing silicon and carbon. A semiconductor, it occurs in nature as the extremely rare mineral moissanite, but has been mass-produced as a powder and crystal sin ...

(S) *

Ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...

Diamond Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the Chemical stability, chemically stable form of car ...

(D, MD, SD) *

Cubic boron nitride Boron nitride is a thermally and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal ...

(CBN) Grinding wheels with diamond or CBN grains are called superabrasives. Grinding wheels with aluminum oxide (corundum), silicon carbide, or ceramic grains are called conventional abrasives.

Grain size

From 10 (coarsest) to 600 (finest), determines the average physical size of the abrasive grains in the wheel. A larger grain will cut freely, allowing fast cutting but poor surface finish. Ultra-fine grain sizes are for precision finish work. generally grain size of grinding wheel are 10-24(coarse),30-60(medium),80-200(fine) and 220-600(very fine).

Wheel grade

From A (soft) to Z (hard), determines how tightly the bond holds the abrasive. A to H for softer structure, I to P for moderately hard structure and Q to Z for hard structure. Grade affects almost all considerations of grinding, such as wheel speed, coolant flow, maximum and minimum feed rates, and grinding depth.

Grain spacing

Spacing or structure, from 1 (densest) to 17 (least dense). Density is the ratio of bond and abrasive to air space. A less-dense wheel will cut freely, and has a large effect on surface finish. It is also able to take a deeper or wider cut with less coolant, as the chip clearance on the wheel is greater.

Wheel bond

How the wheel holds the abrasives; affects finish, coolant, and minimum/maximum wheel speed.

Types

Straight wheel

To the right is an image of a straight wheel. These are by far the most common style of wheel and can be found on bench or pedestal grinders. They are used on the periphery only and therefore produce a slightly concave surface (''hollow ground'') on the part. This can be used to advantage on many tools such as chisels. Straight Wheels are generally used for cylindrical, centreless, and surface grinding operations. Wheels of this form vary greatly in size, the diameter and width of face naturally depending upon the class of work for which is used and the size and power of the grinding machine.

Cylinder or wheel ring

Cylinder wheels provide a large, wide surface with no center mounting support (hollow). They can be very large, up to 12" in width. They are used only in vertical or horizontal spindle grinders. Cylinder or wheel ring is used for producing flat surfaces, the grinding being done with the end face of the wheel.

Tapered wheel

A straight wheel that tapers outward towards the center of the wheel. This arrangement is stronger than straight wheels and can accept higher lateral loads. Tapered face straight wheel is primarily used for grinding thread, gear teeth ...

Straight cup

Straight cup wheels are an alternative to cup wheels in tool and cutter grinders, where having an additional radial grinding surface is beneficial.

Dish cup

A very shallow cup-style grinding wheel. The thinness allows grinding in slots and crevices. It is used primarily in cutter grinding and jig grinding.

Saucer wheel

A special grinding profile that is used to grind milling cutters and twist drills. It is most common in non-machining areas, as sawfilers use saucer wheels in the maintenance of saw blades.

Diamond wheels

''Diamond wheels'' are grinding wheels with industrial diamonds bonded to the periphery. They are used for grinding extremely hard materials such as carbide cutting tips, gemstones or concrete. The saw pictured to the right is a slitting saw and is designed for slicing hard materials, typically gemstones.

Mounted points

''Mounted points'' are small grinding wheels bonded onto a mandrel. Diamond mounted points are tiny diamond rasps for use in a

jig grinder A jig grinder is a machine tool used for grinding complex shapes and holes where the highest degrees of accuracy and finish are required. The jig grinder is very similar to a jig borer, in that the table positioning and spindles are very accu ...

doing profiling work in hard material. Resin and vitrified bonded mounted points with conventional grains are used for deburring applications, especially in the foundry industry. Mounted points is a small handle with a general name, used in electric mill, hanging mill, hand drill. Many of the main types of ceramic mounted points, rubber mounted points, diamond mounted points, emery cloth and so on. Ceramic mounted points: granular sand (usually corundum, white jade, chrome corundum, silicon carbide) made of ceramic binder sintering, the central supplemented by metal handle. Mainly grinding all kinds of metal, for the diameter of the inner wall of the grinding, mold correction. Rubber mounted points: finer particle size sand combined by rubber binder Into, for the polishing of the mold. sandpaper mounted points: Multi-piece rectangular sand cloth, bonding around the metal handle. Granularity is generally in the 60 # -320 #, for the diameter of the inner wall of the polishing. Diamond mounted points: A grinding tool for non-metallic materials such as stone, porcelain and the like, and more particularly to a grinding tool using a diamond alloy as a grinding body comprising a substrate and a plurality of grinding bodies, And the substrate is preferably made of an adhesive material having a certain toughness, and the grinding body is preferably made of a diamond alloy material, and the substrate is preferably made of a diamond alloy material, The utility model has the characteristics of high grinding performance, simple manufacture and low cost, high grinding quality and can be applied to large-scale grinding.

Cut off wheels

''Cut off wheels'', also known as ''parting wheels'', are self-sharpening wheels that are thin in width and often have radial fibres reinforcing them. They are often used in the construction industry for cutting

reinforcement bar Rebar (short for reinforcing bar), known when massed as reinforcing steel or reinforcement steel, is a steel bar used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension ...

s (rebar), protruding bolts or anything that needs quick removal or trimming. Most handymen would recognise an

angle grinder An angle grinder, also known as a side grinder or disc grinder, is a handheld power tool used for grinding (abrasive cutting) and polishing. Although developed originally as tools for rigid abrasive discs, the availability of an interchangeable ...

and the discs they use.

Use

To use the grinding wheel it must first be clamped to the grinding machine. The wheel type (''e.g.'' cup or plain wheel below) fit freely on their supporting arbors, the necessary clamping force to transfer the rotary motion being applied to the wheels side by identically sized flanges (metal discs). The paper blotter shown in the images is intended to distribute this clamping force evenly across the wheels surface.

Dressing

Grinding wheels are self-sharpening to a small degree; for optimal use they may be dressed and trued by the use of wheel or grinding dressers. ''Dressing'' the wheel refers to removing the current layer of abrasive, so that a fresh and sharp surface is exposed to the work surface. ''Trueing'' the wheel makes the grinding surface parallel to the grinding table or other reference plane, so that the entire grinding wheel is even and produces an accurate surface.

Testing for grinding tools

Grinding wheels and grinding tools are used extensively in industry and manual trades for treating surfaces and for separating and cutting objects and have to withstand massive mechanical stress. Mostly centrifugal forces can cause a break, but also flexural and shear forces. Since a break or failure of the grinding tool can present a severe hazard to people and machinery due to the high levels of energy released, high standards are placed on the mechanical and breaking strength of grinding tools in the European safety standards. The

Institute for Occupational Safety and Health of the German Social Accident Insurance The Institute for Occupational Safety and Health of the German Social Accident Insurance (German: ''Institut für Arbeitsschutz der Deutschen Gesetzlichen Unfallversicherung'', ''IFA'') is a German institute located in Sankt Augustin near Bonn and ...

conducts tests based on the "Rules of Procedure for Testing and Certification carried out by the Testing and Certification Bodies in DGUV Test".

References

{{DEFAULTSORT:Grinding Wheel Grinding and lapping Metalworking tools