Chip forms in Turning

Basic Chip Forms in Turning

Chips Forming while turning

Basically, there are three types of chips obtained while turning different materials on lathe. These are

Types of Chips

1.     Segmental Chips (Tear Chips)

This type of chips are produced while turning brittle materials like cast iron, Brass etc. with very small or zero rake angle on the tool. In this case, a smooth surface is produced on the work piece. Also, tool like is good and power consumption is low.

Tear Chips may also be produced while turning ductile materials like steel, copper, Aluminium etc. In this case, the effects are:-

         i.            Poor Surface Finish on the work piece

       ii.            High cutting force

      iii.            More power consumption

     iv.            Shorter tool Life

The reasons for tear chips on ductile materials are:

·         Small rake angle on the tool

·         Low cutting speed

·         High Depth of cut

These conditions must be corrected.

2.     Continuous chips with built up edge (Shear Chip)

This type of chip is sometimes produced on ductile materials under unfavorable conditions. This is bad because, its effects are

         i.            Poor Surface Finish on work piece

       ii.            High cutting force

      iii.            Shorter tool Life

The Causes for such chips are:-

·         Less Cutting Speed

·         High Depth of Cut

·         Small rake angle on the tool

·         High friction between chip and tool face due to lack of proper lubricated and very rough tool face.

3.     Flowing Chip

This type of chip is obtained while turning ductile materials under favorable conditions. These conditions are:-

         i.            Proper cutting speed

       ii.            Big rake angle

      iii.            Slow feed

     iv.            Reasonable Depth of cut

       v.            Keen Cutting edge

     vi.            Low Co efficient of Friction between chip and tool face brought by

·         Good Finish on the Work piece

·         Low cutting Force

·         Long tool life

Chip Breakers

It is necessary on lathes to break the long continuous chips into small pieces for easy disposal and to reduce danger to the operator and machine, For this Purpose, various types of chip breakers are Provided and turning tools. The common types of Chip Breakers are

Parallel step and Angular Step Chip Breakers.

1.       Parallel Step Type

2.       Angular Step Type

3.       Groove Type

4.       Clamp Type