Whirling & CBN Simplify Hard Part Operations
Hard part machining is the manufacturing process that many industries are turning to. The
Aerospace segment uses CBN cutting tools to make landing gear struts, also Automotive manufacturers
use it for steering worms and worm gears, the Medical field for implants and the Machine Tool industry
for ball screw manufacturing. All rely on Cubic Boron Nitride (CBN) inserts to machine hardened
Today’s CBN grades are far more versatile than they were a few years ago. Manufacturers used to
avoid using CBN even on mildly interrupted parts because of its fragile nature, but now CBN grades
can cut through even severely interrupted parts without a problem.
Using a Cubic Boron Nitride cutting tool material, steels as hard as 65 HRc can be machined.
CBN has a uniform high hardness and excellent abrasion resistance in all directions. Edge retention
permits more effective cutting with less tool wear, which helps maintain part geometry of greater
precision and consistency.
An innovative break-through has been the introduction of CBN cutting tools into the whirling process.
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.
A hard-whirled 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.
Finish thread grinding is one of the most time-consuming operations on long screws,
taking up to 16 hours per work-piece. 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.