Finish milling of ductile iron with PCBN 03:59

Grey cast iron and ductile (nodular) cast iron are the two main types of cast iron used in today’s industry. The main difference is how the graphite appears. In grey cast iron, the graphite is in the form of flakes, while in ductile iron, the graphite is in the form of nodules. The composition is basically the same, but the demand for purity requires the Sulphur content to be very low in nodular iron.      


Both grey cast iron and ductile cast iron are very abrasive materials, but ductile iron is regarded as the more difficult one to machine. Ductile iron components can be various housings, shafts and other components mainly for the automotive segment.


Generally ductile iron is machined with carbide inserts, both roughing and finishing. When there are high requirements on dimensional tolerances and surface finish, PCBN can be an alternative for the finishing tool. The higher wear resistance of PCBN allows for longer tool life with maintained edge quality, resulting in superior tolerances and surface finish.


Rough milling is best done with wear resistant carbide grade. Seco’s range of milling grades for ductile cast iron include MP1500 and MK2050.



For finish milling, Seco’s CBN200C is the preferred grade. Grade CBN200C combines the optimum balance between substrate, coating and edge preparation for successful finish machining of high quality ductile iron components.

Depth of cut should be kept as low as possible, 0.1-0.3 mm. Cutting data is similar for carbide and PCBN, about 500 m/min, and feed rates will in finishing depend on surface finish requirement, but is in the range of 0.1 – 0.2 mm/tooth. Wiper technology will allow for higher feed rates while maintaining surface finish.

For more information, please contact your local Seco representative, or our PCBN team.

Author: Henrik Sandqvist Product Specialist SECOMAX PCBN/PCD SECO TOOLS Shanghai CO., Ltd. Level 2, Building 8, 456 HongCao Rd., Shanghai 200233, China Office: +86 21 5426 5849 Mobile: +86 186 167 90063 e-mail: henrik.sandqvist@secotools.com