The hard-whirling ball screw can be machined to finished dimensions and tolerance without further machining. On screws that demand thread grinding, the hard whirling process can still save on machining time and operation elimination.
By machining the thread profile to nearly ground accuracy, hard whirling reduces the amount of material to be ground, thus reducing grinding time to less than two hours. This allows ball screw manufacturers to stock pre-hardened bars, eliminating a very lengthy heat treating process. This greatly reduces the total ball screw manufacturing time.
The combination of today’s latest CBN material with the smooth tangential cutting action of whirling results in a revolutionary process for cutting threads in hard materials.
Hard whirling is done dry, without coolant. The chips carry away nearly all of the heat during cutting, leaving the workpiece cool and minimizing any thermal geometry variations. The surface finish and profile accuracy are close to grinding quality.
Many ball screw manufacturers are discovering that hard whirling can eliminate a number of previous mandatory operations in their process. For example, a ball screw would be rough- machined in the soft state, case hardened, straightened and then finish ground.