Automotive parts maker GKN Hardy Spicer has halved costs on part of its drive-shaft production process by using one hard-turning machine rather than two grinders. Crucial to the development is the use of superhard cubic boron nitride (CBN) tooling.
The driveshaft, used in front and four-wheel drive applications, has a constant velocity joint whose outer race has some particularly tricky features to machine.
Grinding the shaft previously caused problems with overheating and cracking because it was hard to project sufficient coolant between the grinding wheel and the metal surface. Using CBN tools, the part can be machined by turning rather than grinding.
CBN is the second hardest known material after diamond. It retains its hardness at temperatures over 1,000 degrees C, so is ideal for cutting hardened steel.
The change allowed GKN Hardy Spicer to replace two grinders with a cycle time of 60 seconds each with one George Kingsbury MHP lathe with a cycle time of 26 seconds.