Engraving can be done on various types of materials like steel, brass, aluminum, copper, wood, plastic, acrylic etc. The right tool has to be used for different materials which will enhance the engraving quality. Wood engraving, plastic engraving and steel engraving requires seperate engraving tools. Carbide tip tools are most commonly used on harder materials like steel, aluminum, brass etc. Whereas HSS tools are most economical to cut soft material like wood, plastic, acrylic. And diamond tools are to be used to engrave on glass, ceramic tiles.

Tool Geometry

Two factors need to be considered - the tool shape and the tool angle.

Tools come in various shapes like conic tools, flat bottomed tools, round bottomed tools etc.
Fine engraving requires a conic tool  whereas removing a lot of material  is done efficiently with a flat bottomed tool. 

Deciding the tool tip and the tool angle takes a lot of practice.  The more the tool angle, the less depth it can achieve.