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.
What are ejector pins?
An ejector pin is a hardened, precision-ground pin mounted in the ejector plate of a mould or die. When the tool opens, the ejector system drives the pins forward to release the moulded part cleanly. Pins run in fitted holes, so diameter tolerance and surface finish directly affect flash, galling and maintenance intervals.
Typical materials
Common grades are SKD61 (H13 equivalent hot-work tool steel, typically nitrided for wear) and SKH51 (M2 high-speed steel) for higher temperature and abrasive resins. Surface treatments such as nitriding improve wear and galling resistance.
Types of ejector pins
Straight ejector pins
The standard form — constant diameter with a cylindrical head. The workhorse for most plastic moulds.
Precision ejector pins
Tighter diameter tolerance and finer surface finish for close-fitting holes and low-flash moulding.
Shouldered / stepped pins
A larger-diameter body stepped to a thin working end — stiffer than a thin straight pin of the same working diameter.
Rectangular (blade) ejector pins
Flat working section for ejecting thin ribs and slots where a round pin will not fit.
Ejector sleeves
Hollow pins that eject around a core pin, used for bosses and circular features.
How to select ejector pins
- Diameter and overall length — matched to the ejector hole with the correct fit.
- Material and hardness — SKD61 for general moulding, SKH51 for demanding or abrasive applications.
- Head type — cylindrical head standard; stepped or blade forms for special geometry.
- Surface treatment — nitrided pins for longer life in high-cycle tools.
- Quantity and repeatability — production tools consume pins as maintenance items.
Not sure? Send what you have — a part number, drawing or photo — and our engineering team will confirm the selection.
Frequently asked questions
- What material are ejector pins made of?
- Most ejector pins are SKD61 hot-work tool steel (H13 equivalent), usually nitrided for wear resistance. SKH51 (M2 high-speed steel) pins are used for higher temperatures and abrasive, glass-filled resins.
- What is the difference between straight and precision ejector pins?
- Both are constant-diameter pins; precision ejector pins are ground to a tighter diameter tolerance with a finer finish, for close-fitting holes where flash and gas venting must be controlled.
- When should I use a rectangular (blade) ejector pin?
- When the part has thin ribs or narrow slots that a round pin cannot reach — the flat blade section ejects along the rib without marking the part face.
- How do I order ejector pins from JIDOKA?
- Send the diameter, length, material and quantity — or simply your existing part number or a drawing — through the Request a Quote form and our engineering team responds with a quotation.
Related components
Punches
Punches do the cutting and forming in press tools. Edge life, shank accuracy and coating decide how many strokes a tool runs between regrinds.
Button Dies
Button dies are the hardened female counterparts to punches — the slug passes through them each stroke. Correct clearance and land geometry control burr height and edge life.
Leader Pins
Leader pins keep the two halves of a die set or mould base aligned through every stroke. Alignment accuracy here protects punches, cavities and product quality.
Die Springs
Die springs pack maximum force into a standard hole — rectangular wire and controlled stress make them the force standard in press tools.
Need ejector pins?
Tell us the specification, quantity and application — or just send the drawing.