Precision Straight Center Pins
Solid straight center pins designed to guide ejector sleeves. Options include tip processing for cosmetic surfaces and venting grooves for gas release.
Products in This Category
JIS Standard SKD61 Steel Straight Center Pins with Tip, Nitrided
Nitrided, precision tip-processed.
JIS Standard M2 Steel Straight Center Pins with Tip Processed
M2 high hardness core pin.
JIS Standard M2 Steel Straight Center Pins with Tip Processed
SKH51 head with M2 shaft construction.
JIS Standard SKD61 Steel Straight Center Pins with Tip Processed - Nitrided
Standard precision ground core pin.
JIS Standard SKD61 Steel Gas Release Straight Core Pins Flat-Sided
Venting slot positioning core pin.
Selection Matrix: Center Pin Tip Geometries
Compare tip-processing styles for straight center core pins:
| Tip Processing Style | Hardness/Tolerance | Flash Protection | Best For |
|---|---|---|---|
| Standard Ground Tip | 48-52 HRC, standard tolerance | Standard parting line seal | General purpose boss molding with regular tolerances. |
| Tip-Processed (Precision Ground) | High-hardness tip, tolerance ≤0.005mm | Extreme flash prevention (zero gap) | High-cosmetic surfaces, transparent components, lenses. |
| Gas Release (Venting Grooves) | Surface nitrided, micro venting grooves | Standard seal, allows gas exit | Deep boss holes with severe gas entrapment issues. |
Selection tip: Tip processing level should match your part's cosmetic requirements — standard ground for hidden features, lapped for optical or medical parts. For a full comparison, see our Tip Processing Comparison Guide.
Venting slot geometry in Gas Release Center Pins
How Gas Release channels safely exhaust trapped cavity air without causing polymer flash:
Vent Slot Micro-Dimensions
The gas release pin features micro-venting flats ground along the tip sides. These channels are engineered with a depth of 0.02mm to 0.03mm. Because standard molten polymer viscosity prevents it from entering gaps smaller than 0.03mm, gas escapes freely while plastic is blocked.
Venting Gas Flow Dynamics
As polymer fills the circular boss cavity, it displaces trapped air. The air flows down the side channels, passes through the sleeve guide bore clearance, and exhausts safely out of the mold base, avoiding high-pressure soot buildup.
Engineering note: Vent channel depth must be sized to your resin's viscosity — too shallow clogs, too deep creates flash. For detailed sizing guidelines, see our Gas Release Center Pins guide.
Application Scenarios: Straight Center Pins
Industrial cases where straight center pin options resolve specific injection molding defects:
Optical PMMA Lenses
Acrylic lenses are highly sensitive to ejector parting lines. Standard pins cause visible ejector ring flash or marks.
Why it fits: Tip-processed center pins feature a ground diameter step with tolerance ≤0.005mm, forming a seamless seal against the sleeve ID.
Gas Entrapment Screw Bosses
Circular screw bosses are blind holes that easily trap gas, leading to structural voiding or carbon burn marks.
Why it fits: Gas Release pins feature flat micro-slots that naturally exhaust trapped air out of the blind hole core.
Frequently Asked Questions
What are the advantages of tip-processed straight center pins (Tip Processed)?+
How does the venting slot geometry in Gas Release straight center pins function?+
What are the standard hardness values for straight center pins made of SKD61?+
About Straight Center Pins
Straight center pins are solid precision-ground rods that sit inside ejector sleeves to form the internal boss core. Available with standard tips, precision-ground tips (Tip Processed) for cosmetic-grade parting lines, and gas release variants with micro-venting slots that prevent burn marks in deep boss cavities. The stationary pin is anchored in the core backing plate while the surrounding sleeve moves.
Engineering Resources
Need a Custom Quote?
Specify pin diameter, length, tip type (standard/precision-ground/gas release), and material. Custom venting slot geometries available for challenging gas trapping applications.