Rigiva (Riva) "Handbook For Milling Operations" Comprehensive 100-page well-illustrated General Operator's Guide For Rigiva Millers. Contains detailed instructions concerning the operation of ordinary processes as well as how to use many of the more complex accessories: Dividing Heads, Bevel Gear Cutting, Universal Dividing Head, Plain and Differential Indexing, Milling Spiral cams, Hob