Nodular cast iron
Material classification: K3.x
The machinability of ferritic and ferritic/perlitic nodular cast iron is very similar to that of low alloyed steel. Therefore, the milling recommendations provided for steel materials should be used regarding the selection of tools, insert geometries and grades.
Perlitic nodular cast iron is more abrasive; therefore, cast iron grades are recommended.
Use PVD coated grades and wet machining for best machining capabilities.
Compact graphite iron (CGI)
Material classification: K4.x
Perlitic content less than 90%
This type of CGI, which often has a perlitic structure of around 80%, is the most common being milled. Typical components are engine blocks, cylinder heads and exhaust manifolds.
Cutter recommendations are the same as for gray cast iron; however, sharper, more positive insert geometries should be selected to minimize burr formation on the component.
Circular milling can be a very good alternative method to conventional cylinder boring in CGI.
Austempered ductile iron (ADI)
Material classification: K5.x
Roughing is normally carried out in the non-hardened condition and can be compared to milling a high alloyed steel.
The finishing operation, however, is performed in the hardened material, which is very abrasive. This can be compared to milling hardened steels, ISO H. Grades with high resistance against abrasive wear are preferred.
Compared to NCI, the tool life in ADI is reduced to approx. 40%, and cutting forces are approx. 40% higher. Read more about cast iron materials
Milling non-ferrous materials
Non-ferrous materials include not only aluminum, but also magnesium-, copper- and zinc-based alloys. The machinability differs primarily depending on the Si-content. Hypo-euthectic aluminum is the most common type, with a Si-content below 13%.
Aluminum with a Si-content below 13%
Material classification: N1.1-3
The dominant wear criteria is built-up edges/smearing on the edges, leading to burr formation and surface finish problems. Good chip formation and chip evacuation are crucial for avoiding scratch marks on the component surface.
- Use PCD-tipped inserts with sharp and polished edges for good chip-breaking capabilities and built-up edge resistance
- Choose positive insert geometries with sharp edges
- Unlike most other milling applications, cutting fluid should always be used in aluminum to avoid smearing on the insert edges and to improve surface finish
- Si-content < 8%: Use cutting fluid with 5% concentration
- Si-content 8–12%: Use cutting fluid with 10% concentration
- Si-content > 12%: Use cutting fluid with 15% concentration
- A higher cutting speed generally improves the performance and does not negatively affect tool life
- An hex value of 0.10–0.20 mm (0.0039–0.0079 inch) is recommended. Values that are too low can lead to burr formation
Warning: Make sure that the maximum rpm for the cutter is not exceeded
Read more about non-ferrous materials
- Due to high table feeds, a machine with a "look-ahead" function should be used to avoid dimensional errors
- Tool life is always limited by the burr formation or surface finish on the component. Wear on the insert is difficult to use as a tool life criteria