Worm gears are not threads and not splines – they need a machine that understands the tooth form. SK6520 is a dedicated 4-axis CNC worm milling machine, not a VMC with threading macros.

Why a dedicated worm mill instead of a universal VMC?

A 5-axis VMC can interpolate a thread path, but it cannot handle the tool engagement and chip load of a form cutter cutting ZI or ZK tooth profiles. SK6520 synchronizes workpiece rotation (C-axis) with table traverse (Z-axis) specifically for worm geometry. The FAGOR 8055i control has worm milling cycles built in – no custom macro programming required.

What tooth forms can this machine actually cut?

ZA (axial straight-sided), ZN (normal straight-sided), ZI (involute) and ZK (K-type) – the four standard worm profiles used in power transmission. The software adjusts helix angle, swivel angle and tool offset for each form. This replaces hobbing machines that are limited to ZA and require a separate grinder for finishing.

What accuracy does a worm mill deliver over a hobber?

P7 grade per GB standard and Ra1.6μm surface finish directly from milling – no post-grinding required for many applications. The workpiece is held between chuck and tailstock with steady rest support, not indexed between passes. This replaces hobbing plus grinding with one machine, one setup, one toolpath.