What method is used for finishing/shaping a machine part made of exceptionally hard materials?

The method for finishing or shaping machine parts made of exceptionally hard materials typically involves the use of abrasive grinding. This process is well-suited for hard materials because it utilizes abrasives that can effectively remove material from surfaces that are otherwise difficult to machine using conventional cutting methods.

Abrasive grinding employs a rotating wheel made from hard materials like corundum or carbide which can wear down even the toughest materials. The grinding process not only shapes the part but also provides a high-quality surface finish. Therefore, for particularly hard materials, abrasive grinding is often the preferred method as it accounts for the material's resistance to deformation and ensures precision.

In contrast, methods like oxygen lancing or using carbide inserts might not be as effective for extremely hard materials. While machining with carbide inserts can be effective in many applications, they may struggle with the highest hardness levels, leading to tool wear and diminished performance. Machining high-speed tool steel is a specialized process that can handle toughness but isn't necessarily tailored for ultra-hard materials in the same way abrasive grinding is.