Core Pins Do More Than Form a Hole
Core pins create internal geometry in molded parts — holes, bosses, and undercuts. They also take the brunt of injection pressure and mold temperature. Selecting the right hardness grade is the difference between a pin that runs for years and one that needs replacing every few months.
DMS Core Pin Hardness Grades
The DMS catalog organizes core pins by hardness class:
- Standard hardness (soft) core pins — for general-purpose molding where wear is moderate. Easier to machine and modify in-house.
- High-hardness (hard) core pins — specified for abrasive resins (glass-filled nylon, PBT, PC/ABS blends) and high-cavity pressures. The harder surface resists erosion and scoring at the pin tip and along the body.
- Copper alloy core pins — the heat-transfer specialists. Copper alloy pins pull heat out of hot spots at the core tip, reducing cycle time and preventing localized shrinkage or sink. They are the go-to for thin-wall parts and hot-runner molds where cooling is the bottleneck.
Ejector Sleeves: The Thin-Wall Solution
An ejector sleeve is a tubular pin that ejects around a core — perfect for thin-wall bosses, standoffs, and parts with small-diameter cores. DMS offers nitrided parallel ejector sleeves in both inch and metric, with through-hard versions for extreme cycles.
The sleeve slides over the core pin, so the molded material is pushed off the core without drag marks. Matching the sleeve ID to the core OD and the sleeve OD to the mold plate hole is the critical fit — DMS publishes the exact tolerances for both.
Practical Selection Rules
- Glass-filled or abrasive resin? → high-hardness core pins.
- Thin-wall part with a hot core? → copper alloy core pin to move heat fast.
- Boss or standoff ejection? → ejector sleeve around the core.
- High cycle count on a demanding mold? → through-hard sleeve.
Stock Availability Matters
When a core pin or sleeve fails mid-production, the lead time for a custom grind is measured in weeks. Standard DMS sizes — including the newer diameters and lengths in the catalog — are stocked by Tooling Components, which means replacement in days, not weeks.
Related catalog item: Tooling Components stocks DMS core pins (standard, high-hardness, and copper alloy), ejector sleeves (nitrided and through-hard, inch and metric), and oversize sleeves for hole repair.
Tell us your resin, cycle count, and core geometry — we will recommend the right grade and size.