Specific cutting force is a frequently used parameter to classify and describe the
energetic environment of mechanical machining operations. It defines the ratio of
cutting forces and theoretical chip section during machining. This definition makes
it possible to create general technological models for precise process planning. Classical
models of cutting forces already indicate that specific cutting force cannot be modelled
using a single low-level analytical function due to the marked presence of size effect.
The problem is amplified in the case of micro-chip forming, where the relative scale
of elastic and plastic deformations in the machined material differ from those experienced
in conventional cutting conditions. Previous research proved that boundaries of specific
cutting forces can be defined by values of exact uncut chip thicknesses, in which
case the sections of specific cutting force may indicate different types of material
deforming processes. The aim of current research presented in this paper is to extend
the empirical model of specific cutting force for fine chip-removing cutting processes
by identifying a new boundary section of uncut chip thickness. Therefore, a new boundary
chip thickness was defined based on data obtained with reference to experimental cutting
force. New boundary chip thickness follows the so-far proven tendencies of already
known section borders and this enables the extension of the validity range of classical
approaches presented by specific cutting force models beyond macro-scaled chip forming
to micro-scaled chip forming processes. The extension of the model considers the effect
of cutting parameters, primarily that of feed rate.
