CNC (computer numerical control) machining allows the production of custom precision parts for scale models. The author worked with a company called HLH Prototypes in China to CNC machine custom side frames for a scale helicopter gearbox. Within 10 days of submitting the 3D CAD file, the author received the finished parts, which fit perfectly and worked smoothly in the assembled gearbox. CNC machining enables hobbyists to design and produce precision custom assemblies for scale models that would otherwise be impractical or expensive to make.