Core Pins
Core pins form the holes and bosses in a moulded part — precision pins that live inside the cavity, cycling with every shot.
What are core pins?
A core pin is a hardened, ground pin mounted in the mould that forms an internal feature — a hole, boss bore or slot — in the moulded part. Where the feature must be ejected, the core pin runs inside an ejector sleeve. Like ejector pins, core pins are standardised consumables ordered by diameter, length and material.
Typical materials
SKD61 (nitrided) standard; SKH51 for fine diameters and abrasive resins.
Types of core pins
Standard straight core pins
Constant diameter with cylindrical head — the base form.
Stepped core pins
Reinforced shank stepped to the forming diameter.
Core pins for sleeves
Sized to run inside a matching ejector sleeve.
How to select core pins
- Forming diameter and tolerance for the part feature.
- Overall length through the stack to the head seat.
- Material/treatment for resin and cycle life.
- Matched ejector sleeve where the feature is sleeve-ejected.
Not sure? Send what you have — a part number, drawing or photo — and our engineering team will confirm the selection.
Frequently asked questions
- What is the difference between a core pin and an ejector pin?
- A core pin forms a feature in the part and normally does not move with ejection; an ejector pin moves forward to push the part off. Where a formed boss must be ejected, the stationary core pin is paired with a moving ejector sleeve.
Related components
Ejector Sleeves
Where a boss must be ejected around its core pin, only a sleeve can push evenly on the ring of plastic — the ejector sleeve is that part.
Ejector Pins
Ejector pins push the finished part off the core when a plastic mould or die opens. They cycle millions of times against heat and friction, so material, hardness and fit decide tool life.
Mould Cooling Components
Cooling decides cycle time. Baffles, plugs and nipples route water through the mould so every cavity region holds the right temperature.
Need core pins?
Tell us the specification, quantity and application — or just send the drawing.