Main Components of Grinding wheel

A grinding wheel is a self-sharpening tool composed of discrete abrasive grains held together by a bonding agent with composite structure of many clearance allowances for the cutting edges. The characteristic of a grinding wheel depends upon the combined elements of abrasive, grit size, grade, structure and bond.

GRINDING WHEEL MARKING

CHEIL GRINDING WHEEL MARKING

The main components of grinding wheel

workpiece

Element Character
Abrasive The abrasive grain is the element that actually performs the cutting activity in the grinding process. And the choice of abrasive grain depends on the material to be ground.
Bond The role of bond is to hold the individual grains together. The type of bond depends on the operating speed of wheel, the type of operation and the surface finish required.
Pore The exists between grains and bond. In order to provide chip clearance, air space(pore) must be existed between grains and bond. Dense spacing is denoted by low numbers and open spacing by high numbers.

ABRASIVE

abrasive

GRIT

The size of abrasive grain is indicated in terms of the mesh (Screen size), coarse grains by low numbers and finer grains by high numbers.

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Coarse grits are in use for soft, ductile, stringy materials for fast stock removal rough grinding, large contact area, and high grinding pressure. Finer grits in use for obtaining smooth finish, hard & brittle materials, small contact area and form holding of small & narrow corners.

grit size of grinding wheels

grid distribution graph

GRADE

The relative holding power of the bond which holds abrasive grains within a wheel-degree of “hardness” of strength is indicated softer grades in low alphabet and harder grades in high alphabet.

Abrasive grains of same size but with heavier bond coating and thicker, stronger bond posts as in a hard grade wheel.
Abrasive grains of same size but with heavier
bond coating and thicker, stronger bond
posts as in a hard grade wheel.
Abrasive grains with light bond coating and weak connecting bond posts as in a relatively soft grade wheel. (Bright areas are the pores, required for chip clearance).
Abrasive grains with light bond coating and weak connecting bond posts as in a relatively soft grade wheel. (Bright areas are  the pores, required for chip clearance).

grade table

Normal Grinding and Abnormal Grinding

STRUCTURE

The relative grain spacing in a wheel. Dense spacing is denoted by low numbers and open spacing by high numbers. Wheel structures are depending upon the material to be ground, rate of stock removal, accuracy and surface finish required.

Structure table

BOND

“Posts” holding abrasive grains in the wheel. The type of bond which depends on the wheel operating speed, the type of operation and the surface finishing required. K-PRIX grinding wheels are made with five types of bonds; (V)Vitrified, (B)Resinoid, (MgO) Oxychloride magnesium, (E)Epoxy, (R)Rubber.

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BOND MARK Manufacturing method Character
Vitrified Ceramic Bond V

Make up of feldspar and clays selected for their fusibility and carefully processed. The pressed blanks are dried in chambers with automatically controlled temperature and then baked in kilns at a temperature about 1300℃.

Porosity and strength of wheels made with this bond give high stock removal and their rigidity helps in the attainment of high precision grinding works. This bond is not affected by water, acid, oils or ordinary temperature variations.

Resinoid Synthetic Resin bond B

The mixture consist of abrasive, synthetic resin and a plasticizer. The blanks are placed in kilns without previously dried. The bonding agent is hardened at temperature between 160℃ and 200℃.

This bond is excellent for cut- off wheels, depressed center wheels, especially for ultra high speed work. Accuracy is not the first considering factor.

MgO Oxychloride Magnesium Bond O

The abrasive grains are added into a mixture of the magnesium oxide and magnesium chloride which is formed and hardened at ordinary temperature.

This bond is excellent for cool cutting even without a coolant and is very suitable for grinding springs, bearing house by double disc grinders. Also, it is widely used in dry grinding works.
Epoxy Epoxy Bond E It is madeup of the mixture of abrasives, Epoxy binder and then hardened at a normal temperature.

The epoxy wheel is not affected by water and acid, and more elastic than resinoid wheel. It is widely used in need of high stock removal works.

Rubber Rubber Bond R It is made with natural or synthetic rubber as a binder and cured at a low temperature.

The rubber wheel which has a good elasticity and strong hardness is used under the wet grinding condition for precision grinding works as the regulating wheels for centerless grinding works. The weakness of the rubber wheels is certainly to be used with the coolant because of a variation by heating at a high revolution  speed.

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