Precision Machining and Surface Treatment Processes

What is a Machining Process?

A machining process is a term used to describe a variety of material removal processes in which a cutting tool removes unwanted material from a workpiece to produce the desired shape. The workpiece is typically cut from a larger piece of stock, which is available in a variety of standard shapes as shown below: flat sheet, I-beam, or rectangular bar.

Common Material Removal Techniques

Turning

Turning is a cutting operation in which the part is rotated as the tool is held on a machine called a lathe. The lathe spins the given product as the blades cut and scrape away the desired areas.

Boring

In boring, a boring tool goes into the workpiece axially and cuts along an internal surface to form different features. Boring is commonly performed after drilling a hole in order to enlarge the diameter.

Grooving and Facing

Grooving is a turning operation in which a single-point tool moves radially. Along the end of the workpiece, removing a thin layer of material to provide a smooth, flat surface is known as facing. The cutting tool moves from the outer diameter to the center or inner diameter of the workpiece, or it can move in the opposite direction. Facing can only be applied if the lathe features a fitted cross slide.

Broaching

Broaching is a machining process that uses a toothed tool called a broach to remove material. A broach is a collection of single-point cutting tools arrayed in sequence, cutting one after the other; each tooth is successively higher than the previous one.

Trepanning

Trepanning is a deep hole drilling process that leaves a core.

Planing and Shaping

Planing is performed on a planer and uses a single-point stationary cutting tool, and the workpiece reciprocates against it, producing a plane or sculpted surface.

Shaping is basically the same as planing, except the workpiece is usually smaller and it is the tool that moves (not the workpiece) horizontally in a reciprocating motion along a slide.

Surface Finishing and Coating Methods

Electroplating

In electroplating, a very thin layer is deposited on an existing object by means of the electrodeposition process. The materials used in the plating (coating) process depend on the composition of the plating bath and the deposition conditions.

Electroforming

Electroforming is the metal forming process where metal is grown by electrodeposition onto a substrate. The electrolytic bath is used to deposit metal like nickel or gold onto a conductive patterned surface.

Lapping

Lapping is a finishing operation where the tool is made of metal or cloth impregnated with very fine abrasive particles. The gap is filled with a slurry containing fine abrasive grains.

Anodizing

Anodizing is a method for changing the surface chemistry of metals.

Burnishing

Burnishing is a cold forming process without actual removal of metal, where a tool is rubbed on the metal surface of the part with enough force to cause plastic flowing of the metal.