... , thank you! (*^_^*) center drill spot drilling center drill set Row socket drillSuper-hard processing of professional, special, non-standard ... we can process according to drawings or samples.Machining case: φ8.50 mill diameter (emulsified liquid), SKD11(HRC62°),rotation speed 1600r ... hole≤2.5*φD(mill Dia.), Precision of processed work piece ≥h9, surface finish more than Ra1.6Extra hard small diameter ...