How to Choose Ejector Pin Material for Plastic Molds

**SKD61 (JIS hot work tool steel)** is the default for most plastic mold ejector pins. It balances hardness (HRC 58–62 after heat treat) with toughness. Use SKD61 when the pin tip is not continuously exposed to melt temperatures above ~600°C and cycle times are normal. **SKH51 / SKH-9 (high-speed steel)** gives higher hardness (HRC 62–65) and better wear resistance on small diameters. Choose SKH51 when pins are thin (under Ø3 mm), high-cycle, or when you see early wear or breakage on SKD61. **Surface treatment:** Nitriding on the head and bearing length extends life without changing core properties. For release problems, polish to Ra 0.2–0.4 μm rather than changing material. **What to put on your drawing:** Material callout, hardness range, nitriding depth if required, and diameter/length tolerances. YZX Precision manufactures to your spec — send CAD or sample for quote.