radius with coefficient of static friction between the roller and the metal surface is given by This is the case when the frictional force on the metal from inlet contact matches the negative force from the exit contact. Surface defect types There are six types of surface defects: Lap This type of defect occurs when a corner or fin is folded over and rolled but not welded into the metal. They appear as seams across the surface of the metal. Mill-shearing These defects occur as a feather-like lap. Rolled-in scale This occurs when mill scale is rolled into metal. Scabs These are long patches of loose metal that have been rolled into the surface of the metal. Seams They are open, broken lines that run along the length of the metal and caused by the presence of scale as well as due to pass roughness of Roughing mill. Slivers Prominent surface ruptures. Surface defect remediation Many surface defects can be scarfed off the surface of semi-finished rolled products before further rolling. Methods of scarfing have included hand-chipping with chisels (18th and 19th centuries); powered chipping and grinding with air chisels and grinders; burning with an oxy-fuel torch, whose gas pressure blows away the metal or slag melted by the flame; and laser scarfing. See also Bernard Lauth, invented and patented the process for cold rolling of iron John B. Tytus, inventor of the first practical wide-strip continuous rolling process for manufacturing steel Tadeusz Sendzimir, whose name has been given to revolutionary methods of processing steel and metals Electron beam texturing, used to apply roughness to the surface of rolling mill cylinders Drawer slides roll forming machine Calender Roll bender Notes Bibliography Doege, E.; Behrens, B.-A.: Handbuch Umformtechnik: Grundlagen, Technologien, Maschinen (in German), 2nd Edition, Springer Verlag, 2010, Further reading Reed-Hill, Robert, et al. Physical Metallurgy Principles, 3rd Edition, PWS publishing, Boston, 1991. . Callister Jr., William D., Materials Science and Engineering - an Introduction, 6th Edition, John Wiley & Sons, New York, NY, 2003. Suhel khan pathan,IJSRDV5I70206 "Three Roller Rolling Machine"(IJSRD/Vol 5/Issue 07/2017/270). External links Metal forming