Construction & Working Principles
Roller burnishing tools incorporate a planetary system of
hardened, tapered rolls which are evenly spaced by a retaining cage. When
a tool engages the workpiece a hardened mandrel is inversely to the taper
of the rolls forces them against the surface of the workpiece.
SELF FEED DESIGN
The rolls axes are set at a slight helix angles to the
axis of the mandrel and workpiece. This angular relationship causes the
rolls to move in a helical path around the workpiece surface thereby establishing
a self feeding characteristic in the tool.
NON - FEED DESIGN
In application where a non-feeding tool is required such
as in close approaches to shoulder or in full bottoming, the tool is conducted
with the rolls axes parallel to the axis of the mandrel. With this construction,
the tool depends on machine feed to advance along the workpiece.
The interaction of the helix angle and the inversely
tapered rolls and mandrel creates the pressure required for roller burnishing.
The pressure is generated because mandrel tends to  overtake
the rolls as the tools feeds along with workpiece. This tendency is restricted
by a stop on the mandrel which establishes a fixed axial relationship between
the rolls and mandrel. Since the rolls mandrel relationship is constant,
the tool maintains a uniform diameter during its complete pass.
AUTOMATIC TOOL RELEASE
The inverse tapers of the rolls and a mandrel provide
the tool with a self-releasing feature. When the advance of the tool in
to the workpiece is stopped, the rollers continue to feed in a helical
path. In so doing, they move forward on the mandrel to oa point where its
diameter is smaller, and the burnishing pressure is released. Only a small
movement is required for the tool to release at which point it can be easily
withdrawn from the workpiece.