Understanding the Metal Burnishing Process

While polishing metal creates a shiny, gleaming surface, burnishing does that and more. Taking advantage of the inherent traits of metal, burnishing reduces surface roughness and increases hardness. Understanding the metal burnishing process will help explain why burnishing is an important step in metal finishing.

Burnishing Tools

While vibratory and rotary deburring machines can perform both polishing and burnishing, using the correct device for the burnishing process is important.

In the metal burnishing process, a hard roller or balls rub against or press on the softer workpiece. This puts stress on the metal being burnished and initiates a process called “cold flow.”

Cold flow happens when malleable metals are put under stress. At some point, the metal begins to yield, causing the metal to smooth itself out. Sometimes the surface is uneven and features tiny peaks and valleys. The “flowing” subsurface evens things out, causing peaks to flatten and valleys to fill. The result is a smooth surface. The process takes advantage of the material’s inherent plasticity to force it to fill in tiny gaps, notches, or dents.

Benefits of Burnishing

In addition to creating a smoother surface, burnishing hardens metal. In fact, burnished metal can be twice as hard as unfinished metal of the same type. The process condenses the metal’s structure, increasing its resistance to fatigue.

Burnishing also reduces the risk of corrosion. The metal burnishing process decreases roughness and removes tiny burrs and dents which can attract rust.

Burnishing lowers manufacturing time by eliminating the extra steps of honing or grinding. Workers can burnish metal parts of different shapes inside and out to refine surfaces and improve performance. And while machines that perform metal burnishing can be expensive, in the long run, they save money by increasing productivity with faster cycles.

AccuBrass supplies a variety of vibratory and rotary deburring machines, including the Mr. Deburr finishing machine. These can remove imperfections like burrs and shards left by cutting machines or lasers. They can also burnish metal to a high degree of smoothness and shine.