Two of the latest technology, five axis wire cutting machines are employed. Both are fully submersible, with auto filtration, water cooling, auto-wire cutting and threading and one micron linear scales.
Photographs:

Cutting a straight sided six spline in a case hardened gear. Inset is the VDU on the CNC control panel.

WIRE CUTTING
An example of an internal, class 5 involute spline, wire cut after case hardening to avoid distortion.