Sumitomo introduces wiper edged CBN inserts for micron fine finishes in hardened steel

The Sumiboron inserts are available in WG for low feed cutting at less than 0.20 mm/rev and WH for higher feed applications, with both insert types developed to enable surface finishes between 1.6 and 3.2 microns to be created. The inserts are also available in three grades: BNC 160, BNC 200 and BN 2000. BNC 160, a 2 micron thickness layer TiAIN+TiCN coated CBN grade, has high wear resistance on a CBN substrate formulated for free chipping from the material being machined. BNC 200, a ceramic film coated CBN grade, has a high resistance to insert damage when turning interrupted surfaces and when removing the carburised layer on hardened steels. Meanwhile, BN 2000 is a non-coated insert grade that has a tough wear and damage resistant cutting edge that uses a high purity ceramic binder and is also suitable for interrupted cutting cycles. In recent trials turning 20 mm diameter shafts in 62 HRc carburised steel, Sumiitomo reports that the Sumiboron WG (BNC 160) insert doubled the number of parts produced per insert to 300. The insert was run at 180 m/min with a feed of 0.1 mm/rev and 0.1 mm depth of cut. A surface finish of 0.8 micron was achieved machining without coolant. Further trials producing stepped diameters, under wet cutting conditions on a hardened pinion gear 58 to 62 HRc, was turned to a surface finish of 3.2 micron using a WH (BNC 200) insert. The operation was run at 130 m/min with a 0.25 mm/rev feed and 0.3 mm depth of cut. The Sumiboron's wiper geometry extended in-cut insert life from 50 to 120 components compared to previous non-wiper operations.