The secondary relief land on an end mill is the additional relieved surface located behind the primary relief land, providing further clearance to minimize friction and extend tool life. It is typically ground at a shallower angle than the primary relief, creating a stepped transition that reduces the amount of tool material in contact with the workpiece.
This feature plays a crucial role in balancing cutting edge durability and heat dissipation. By gradually reducing material contact, the secondary relief helps prevent excessive rubbing, which can lead to heat buildup and premature tool wear. It also strengthens the cutting edge by supporting the primary relief land, making the tool more resistant to chipping or edge failure.
The presence and design of a secondary relief land depend on the end mill’s intended application. High-performance tools or those designed for harder materials often incorporate a well-defined secondary relief to enhance cutting efficiency while maintaining tool stability.
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