Question

Name and briefly describe the four types of chips that occur in metal cutting.

Answer 1

Types of chips

The three common types of chip from a single point tool are.

1;:Discontinuous or segmental chip:                         

Discontinuous chips is formed by a series of rupture occurring approximately perpendicular to the tool place face’ each chip element passing off along the tool face the chip  element’ in the form of small segment may adhere loosely to each other and becomes slightly longer.

2: Continuous Chips:

Continuous chips are formed by the continuous plastic deformation of metal without fracture in front of the cutting edge of the tool and is formed by the smooth flow of the chip  up the tool face. Mild steel and copper are considered to be most desirable materials for obtaining continuous chips. The chips obtained have same thickness throughout. This type of chip is the most desirable. Since it is stable cutting, resulting in generally good surface finish.

3: Continuous Chip with Built up Edge:

This type of chip is very similar to the continuous chip. With the difference that it has a built up edge adjacent to tool face and also it is not so smooth. It is obtained by  machining on ductile material, in this condition of high local temperature and extreme pressure in the cutting and high friction in the tool chip interference, may cause the work material to adhere or weld to the cutting edge of the tool. Successive layers of work material are then added to the built up edge. When this edge becomes larger and unstable , it breaks up and part of it is carried up the face of the tool along with the chip while the remaining is left over the surface being machined, which contributes to the roughness of the surface. The built up edge changes its size during the cutting operation. It first increases , then decreases, then again increases etc.

4:Serrated Chips:

These are semi-continuous . They posses a saw tooth profile. The main reason reason for this appearance is the alternating high shear strain followed by a low shear strain. These chips are seen metals like titanium alloys, austenitic stainless steel and nickel based super alloyswhich are very difficult to machine. When materials are cut at very high speed these chips are likely to be formed.