Characteristics of uncurled and reversely curled chip during orthogonal cutting

It has long been recognized that initially continuous chips are born curled. In this paper a new pattern of chip curl—reverse chip curl, named as chip down-curl, is observed during manufacturing of staggered integral high-finned tube using orthogonal planing with tools with flat rake face when rake angle is large enough and cutting thickness is small. With the increase of cutting thickness or decrease of rake angle, chips become uncurled and further increase of cutting thickness or decrease of rake angle leads to chip up-curl. The variations of chip curvature and conditions under which chips do not curl are obtained by experiments. The mechanisms of uncurled and reversely curled chip formation are investigated by analyzing microstructure of chip root. It is found that the uneven deformation that occurs on cross-section of chip results in reversely curled chip formation and no visible shear deformation that occurs on the primary shear zone of chip leads to uncurled chip formation.