Burnishing is the process of rubbing metal with a small hard tool, which can be either a ball type or roller type, to compact the surface. It is a very useful finishing technique that can increase the workpiece surface finish as well as add microhardness. Burnishing is also known by various other names such as:
The burnishing process is one of the more advanced finishing techniques in which no chips are produced and material is not removed from the surface of the workpiece.
It is dependent on pressing a rolling tool against the workpiece surface. Plastic deformation or physically changes of a surface, due to sliding contact with another object, is achieved using this technique.
The process of burnishing can be done using a sliding surface when the local contact stress exceeds the yield strength of the material.
Burnishing can be carried out in a number of different ways. It simply requires rubbing the burnishing tool with the workpiece with enough force to produce the plastic deformation. You can use a dedicated machine for this purpose or it can be done on a regular lathe or milling machine.
In dedicated machines, the tool is attached to a motor that rotates around the workpiece. The workpiece is attached to the machine using a wise or magnetic table. When the rotating burnishing tool touches the workpiece it applies a degree of force. As the workpiece is moving from left to right, the process of burnishing will take place.
There are two main ways to inspect and rate the burnishing process:
The direct measuring option is able to determine a numerical value to the surface finish allowing you to compare and contrast with other burnishing processes.
The most popular instruments used are stylus probes which operate on electrical principles. Moving the stylus generates a voltage signal, and there are pneumatic elements used to measure the actual surface finish.
There are two main ways in which burnishing is executed which are known as:
This is a cold working process technique, which produces a super finish/fine surface when hardened rollers are moved/turned on the surface of the material.
Ball burnishing creates a super finish often used when looking to produce a specific colour/luster on the surface of the workpiece. In this process, a hard ball is pressed against the workpiece surface.
The burnishing process is mostly carried out on soft metals such as aluminum, brass, zinc and plastics. It can also be performed on low carbon steel alloys.
The process of burnishing is regularly used with an array of different products such as:
 Engineering metrology by Er. R.K Jain Khanna publisher.
 Environmental engineering (McGraw hill series) by Howard S Peave