For finish turning hardened steel, the CBN content of the pcbn inserts is relatively low. Fine grained CBN is generally used for finishing. 

CBN is an extremely hard tool material second only to diamond. Generally, it works best when the material hardness is greater than HRC48 (CBN wears quickly when processing

soft materials). Grades with low CBN content are more brittle than those with high CBN content But they are better for hardened ferrous metal processing. Their lower thermal 

conductivity and relatively higher compressive strength to withstand the heat generated by high-speed cutting and negative rake angles. The higher temperature in the cutting zone

softens the workpiece material and helps chipbreaking, while the negative rake angle strengthens the tool, stabilizes the cutting edge, increases tool life, and allows cutting depths 

smaller than 0.25mm.

Because CBN cutting tools can achieve surface finishes better than 0.4µm and maintain coaxiality of ± 0.012mm, dry-turn hardened workpieces are often an attractive alternative 

to dirty, intensive cooling grinding solutions. Although CBN is a tool material that is particularly preferred for hard turning and high-speed milling, the application scope of ceramics 

and CBN has an amazing overlap.