Material Machining Views: 7

Notes for machining tool steel (T8, T10, Cr12, W18Cr4V), spring steel (65Mn, 60Si2Mn) and bearing steel (GCr15, GCr15SiMn) with countersinks: Common characteristics: 1) High carbon content - 0.6%-1.5% carbon: hard and wear-resistant after hardening; 2) Many alloying elements - chromium, silicon, manganese, vanadium, tungsten: abrasive, wears tools; 3) Hard after hardening - HRC55-65: standard HSS cannot cut it; 4) Soft when annealed - HB200-250: easy to machine. Which tool: 1) Annealed - cobalt HSS (HSS-E) + TiN or TiAlN: good life; 2) Hardened (HRC45-55) - carbide + AlCrN; 3) Hardened above HRC55 - CBN or ceramic. Parameters: 1) annealed - 600-1200rpm, feed 0.06-0.12mm/rev; 2) hardened - 150-400rpm, feed 0.02-0.05mm/rev. Notes: 1) these steels are very hard after hardening - confirm the state (annealed or hardened) before choosing a tool; 2) spring steel is elastic and springs back: sharp tools, small feed; 3) bearing steel is high in chromium and abrasive: wears faster than carbon steel; 4) tool steel contains hard tungsten/vanadium carbides: abrasive wear is severe - prefer carbide or coated tools.