This photo shows the hardened pattern of a ball screw.

For large diamater ball screw hardening:
　◆ Traditional method: only harden the screw teeth, not the groove
　◆ Fuji Denshi method: achieves casing on both teeth and grooves

Fuji Denshi ball screw hardening:
　◆ Using our original line coil, current flows alonf the workpiece axis,
　 achieving hardening in the ball grooves.
　◆ With our original quenching method, uneven casing and cracking
are prevented.
　◆ The support roller minimizes runout during the entire process.