Abrasives

Abrasives

Definition
Abrasive are hard substances used for polishing shaping operations. They are characterized by high melting point high hardness chemically inactive.

Properties of abrasives

1. Hardness
It is the ability of an abrasive to grind or scratch away other materials. The harder the abrasive quicker will be its abrading action. Hardness of the abrasive is measured on Moh’s scale or Vicker’s scale.

Measurement of hardness using Moh’s scale.
Moh’s scale is a scale, in which common abrasives (natural or artificial) are arranged in the order of their increasing hardness.

Soft abrasives
Abrasives having their hardness 1-4 in Moh’s scale are know as abrasives.

2. Toughness
Abrasive are generally hard and brittle, which is otherwise known as toughness.

3. Abrasive power
It is the strength of an abrasive to grind away another materials. It depends on hardness, toughness and refractoriness.

Characteristics of abrasives
The following are the important characteristics of an abrasive.

(a) It should be very hard.
(b) It should resist the abrading action.
(c) It should be chemically inactive.
(d) It should possess high refractoriness.
(e) It should have high melting point.
(f) It should not be affected by frictional heat.

Classification of abrasives
Abrasive are classified into two types
1. Natural abrasive
(a) Nonsiliceous abrasive (d) Siliceous abrasives
2. Artificial or synthetic abrasive