This system is the first to be introduced here from the point of view of chip formation. Z′ is parallel to z and z′, still in the cutting direction, but X′ is normal to, and Y′ is in, the plane containing the cutting and chip velocities. In terms of the chip flow direction projected in
the x′–y′ plane, defined by h′ (different from but related to h ) the transformation from (X′,
c c
Y′, Z′) to (x′, y′, z′) is