For the purpose of this subpart:

(a) The “core” of the forging subcategory shall include forging, artificial aging, annealing, degreasing, and sawing.

(b) The term “ancillary operation” shall mean any operation not previously included in the core, performed on-site, following or preceding the forging operation. The ancillary operations shall include forging air pollution scrubbers, solution heat treatment, and cleaning or etching.