Part Preparation for Burnishing

The “Boring Bar Style” roll burnishing tool consists of a carbide roll which rotates on a precision bearing and applies a pressure both axially and radially to the component surface. The roll will produce tens of thousands of bores in normal use and can be repaired so extending the working life of the roll.

Components are normally pre-turned before burnishing and provided the pre-finish is uniform and tear-free, with no deep gouges, a consistent burnished finish will be achieved. The tool can also be used on ground parts where a burnished texture is required with very tight geometric tolerances.

Three factors that affect the finish achieved by burnishing are the feed pattern, cutting tool geometry and stock allowance.

A smooth bore is NOT necessary as sufficient peak and valley height is required for successful burnishing. The better the pre-machined finish, and the lower the ductility of the material, the less material can be displaced. Any deep gouges and tear marks are likely to remain visible after burnishing.

Prepare the part so a 2µm to 3µm (80 – 120 CLA) uniform and tear free surface is generated. An insert with a 0.8mm (0.032”) radius is ideal for most materials although on less ductile materials a larger radius may be required.

Refer to the stock allowance chart for guidance on pre-sizing of the component.

Part Preparation
  • The amount of stock allowance varies with work conditions, material properties, wall thickness, nature of the pre-machined surface and the quality of surface finish required.
  • Low ductile materials with <18% elongation and maximum 45HRc hardness (i.e. nodular iron, alloy steels, magnesium alloys and copper alloys) should be burnished using the lower stock allowance figures and with a 1.5µm to 2µm (60 – 80 CLA) prepared surface finish.
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