Pin Specs Matter More Than Most Shops Realize
An ejector pin is a precision wear part, and its heat treatment determines how it behaves in the mold. The DMS Components ejector pin line — the catalog Tooling Components references and stocks — offers two fundamental options: nitrided pins and through-hardened nitrided pins. Choosing between them is a matter of matching the hardness profile to the ejection job.
Nitrided Ejector Pins: Hard Surface, Tough Core
Nitrided pins (the EP series in the DMS catalog) are made from AISI H13 (1.2344) tool steel, hardened and then nitride-treated on the surface. The result is a distinct two-zone hardness profile: a surface hardness of 65–75 Rc for wear resistance against the mold and the plastic, and a core hardness of 39–43 Rc for toughness and resistance to bending. The head is annealed to 30–35 Rc so it can flex slightly under load without cracking, and the working finish is held to 8–10 RMS with a maximum 1/32 in. radius on the tip.
Nitrided pins are the standard choice for general ejection duty: clean wear resistance, good dimensional stability, and a cost profile that makes them the default for most mold builds.
Through-Hardened Nitrided Pins: For Slender, High-Load Pins
Through-hardened pins (the RHX series) take a different approach: the entire pin is hardened through, then nitrided on the surface. The catalog shows a surface hardness of 65–74 Rc with a core hardness of 50–55 Rc — a significantly harder core than the standard nitrided pin. That extra core hardness resists bending and peening in slender pins, thin ejectors, and pins that take heavy ejection loads on a small diameter.
The trade-off is toughness: a harder core is stiffer and less forgiving under side loading or misalignment. Through-hard pins belong where the pin is the weakest link in the ejection system — long, small-diameter pins and pins ejecting stiff, high-shrinkage materials.
Reading the DMS Ordering Code
DMS pins order by catalog number plus overall length. A nitrided parallel pin example is EP04 with a 6-inch length ordered as EP04L06P; a through-hard pin uses the RHX prefix, such as RHX-03L06. Shoulder versions add the shoulder diameter to the code (for example, EP04L06-1/2). Sizes marked in blue print in the catalog are available but generally not stocked — check before scheduling a build around them.
A Practical Rule of Thumb
Start with nitrided EP pins for standard cores and cavities. Step up to through-hardened RHX pins when the pin is long relative to its diameter, when ejection loads are high, or when you are seeing bending and peening rather than surface wear. When you see surface wear only, the fix is usually better ejection geometry or a harder surface — not a harder core.
Tooling Components stocks both DMS nitrided and through-hardened ejector pins in inch and metric sizes. Call (800) 992-4766 or visit www.toolingcomponent.com.