One Step Ejector Pins

The minimum practical head-to-shaft diameter ratio is 1.5:1 — for example, a ø6mm head with a ø4mm shaft. Below this ratio, the stress concentration at the step transition becomes excessive, leading to premature breakage. The standard catalog offers ratios from 1.5:1 up to 5:1 (e.g., ø10mm head with ø2mm shaft). For ratios above 3:1, MISUMI recommends specifying a fillet radius of R0.3–R0.5mm at the step transition to reduce stress concentration. The most common ratio in production molds is 2:1 to 2.5:1, which balances ejection area coverage with shaft rigidity.

One-step ejector pins are available in four material grades: (1) M2 steel (SKH51) — HRC 60–62, the standard choice for general-purpose molding at temperatures up to 200°C. (2) H13 nitrided (SKD61) — HV 900+ surface hardness, recommended for glass-fiber-filled resins and mold temperatures above 200°C. (3) M2 chrome-plated — HV 800+ surface, provides improved release for sticky resins like PVC, POM, and TPE. (4) Extra-precision M2 — h5 tolerance (±0.005mm), for molds requiring minimal bore clearance. 17 product series cover these material/tolerance combinations in JIS head standard.

Yes — taperless stepped ejector pins with built-in gas vent channels are available as a separate product category (12 series). These combine the stepped geometry with precision-machined vent grooves along the shaft for simultaneous gas release during ejection. If you need a standard one-step pin with gas venting, the alternative is to pair a standard one-step pin with a separate gas vent sleeve, or to switch to the taperless gas vent series which offers both features in a single component. See the Taperless with Gas Vent category for the combined product.