Rapid machining of hardened AISI H13 and D2 moulds, dies and press tools

Tools and dies for the forging, die casting and plastics moulding industries are commonly made from AISI H13, heat treated to 48–52 HRC, while the press tool sector predominantly uses AISI D2 at a significantly higher hardness of 60–62 HRC. Over the last 10 years, the introduction of high speed end milling has enabled the direct manufacture of prismatic components in the hardened state. The paper briefly outlines such techniques and details published machinability data. Following on from this, experimental work is presented on the drilling of hardened AISI H13 using carbide tooling, together with research on ancillary drilling and tapping operations on hardened AISI D2. When through drilling AISI H13, it was possible to produce up to 210 holes (16mm deep), with a cutting speed of 30m/min and a feed rate of 0.1mm/rev. Drilling data are also presented on the use of water-based electrical discharge machining (EDM) dielectric fluids as a replacement for a conventional soluble oil cutting fluid to allow hybrid HSM/EDM on one machine tool. When drilling and tapping D2, tool life was low with six and nine holes, respectively. Finally, case study work is detailed, relating to the production of AISI D2 automotive press tool parts, in which traditional manufacture is compared with high speed machining (HSM) techniques, using both indexable and solid coated carbide cutting tools. When producing accurate radii on one component, the manufacturing time was cut by 75% using the HSM approach, despite the relatively poor tool life performance detailed above.