Rona 4 piece hss tin milling drill set 3 5 6 5 8mm rona 829027 these top quality drill bits from rona are made from hss steel with a titanium nitride coated surface giving a lifespan up to six times that of regular drill bits they are ideal for enlarging holes cleaning deburring and rounding off internal cut outs in metal wood and plastic rona 829027 hss tin milling drill set 3 5 6 5 8mm