Pin Gate Extension Bushings
M2/P21 steel extension bushings that increase the effective gate bushing length for molds with thick plate stacks or non-standard runner-to-cavity distances.
Products — 1 Variant
Pin Gate Extension Bushing — M2/P21 Steel
SKH51 or P21 steel, configurable length
How Pin Gate Extension Bushings Work
Function
In three-plate molds with thick plate stacks, the distance from the runner plate to the cavity plate may exceed the maximum available length of standard pin-point gate bushings. A pin gate extension bushing bridges this gap by inserting between the gate bushing and the cavity plate.
Installation
The extension bushing sits in the same bore as the gate bushing, extending the resin channel from the gate bushing tip to the cavity entry point. The internal bore of the extension aligns with the gate bushing's tapered channel, maintaining uninterrupted flow.
Length Calculation
Required extension length = Total plate stack distance − Standard gate bushing length − Gate tip protrusion into cavity plate. Example: If your plate stack is 120 mm, standard gate bushing is 80 mm max, and tip protrusion is 5 mm, extension length = 120 − 80 − 5 = 35 mm.
Engineering note: Always verify that the combined gate bushing + extension length matches your actual plate stack within ±0.1 mm. For detailed sizing guidance, see our Pin Gate Extension Bushing Guide.
Extension Bushing vs. Longer Gate Bushing
✅ Use an extension bushing when:
- Plate stack exceeds the maximum standard gate bushing length
- You want to standardize on common gate bushing lengths and adjust only the extension per mold
- You need to mix and match different gate bushings (steel/carbide) with the same extension
- The mold design requires modular assembly for maintenance access
🔀 Use a longer gate bushing instead when:
- A configurable tip length gate bushing can reach the required distance in one piece
- Minimizing the number of bore joints is critical (fewer joints = better flow alignment)
- The total required length is within standard gate bushing range
Decision rule: If a configurable-length gate bushing can reach the cavity in one piece, use it. If not, add an extension. Extensions are also useful when you want to standardize gate bushings across multiple molds with different plate thicknesses.
About Pin Gate Extension Bushings
Pin gate extension bushings are available in two steel grades: SKH51 (AISI M2) for maximum hardness and wear resistance, and P21 (pre-hardened mold steel) for good toughness at a lower cost. Both grades are heat-treated to match the hardness range of standard gate bushings.
Application Scenarios
Extension bushings are needed in specific mold configurations:
Thick Plate Stack Molds
Three-plate molds with combined plate thickness exceeding standard gate bushing maximum length (typically 80–100 mm).
The extension bridges the gap between the gate bushing tip and the cavity plate without requiring a non-standard custom gate bushing.
Multi-Mold Standardization
Production facility running multiple molds with different plate thicknesses but the same gate geometry.
Standardize on one gate bushing length and vary only the extension length per mold. Reduces inventory SKUs and simplifies spare parts management.
Frequently Asked Questions
Why would I need a pin gate extension bushing instead of a longer gate bushing?+
What steel grades are available for pin gate extension bushings?+
How do I calculate the required extension length for my mold stack?+
Engineering Resources
Need a Custom Quote?
Specify your required extension length, bore diameter, and steel grade (M2 or P21). Custom lengths cut to your plate stack measurement.