FACTORS INVOLVING FORMATION OF HELICAL ROLLING MARKS ON INNER SURFACE OF SHELL PRODUCED WITH SMALL TWO-HIGH ROTARY PIERCER AND MEASURES TO REDUCE THE DEFECT

For the small two-high rotary piercer product, serious inner surface helical rolling marks might be caused due to improper operational tooling design and adjustment. Factors involving formation of the said defect are analyzed and the measures to reduce the defect and their actual effect introduced in this paper.