Leader Pins
Guide pins that align mold halves during close — available in straight, stepped, oil-free, and guiding assist configurations for every mold design.
Leader Pins Categories
Straight Leader Pins
Standard cylindrical guide pins for general-purpose mold alignment. The most widely used type, available in JIS and DIN standards.
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Stepped Leader Pins
Guide pins with diameter transitions for multi-plate molds and three-plate designs where different plate thicknesses require stepped engagement.
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Guiding Assist Pins
Secondary guide pins positioned at the outer edges of large mold plates to provide additional alignment support and reduce plate deflection.
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Oil-Free Leader Pins
Self-lubricating guide pins with embedded solid lubricant. Eliminate oil contamination for cleanroom, food-grade, and medical mold applications.
View ProductsHow to Choose the Right Leader Pin Type
Leader pin selection depends on your mold structure, plate count, and operating environment. Follow this two-step process to identify the right type.
Step 1: Match Your Mold Structure
| Selection Criteria | Straight | Stepped | Guiding Assist | Oil-Free |
|---|---|---|---|---|
| Mold Type | Two-plate standard molds | Three-plate molds, multi-plate stacks | Large molds (>500mm), high-precision molds | Cleanroom, food, medical molds |
| Pin Geometry | Uniform diameter throughout | 1-2 step diameter transitions | Uniform, smaller diameter than main leaders | Uniform, with solid lubricant pockets |
| Typical Diameter | 16 – 40 mm | 20 – 50 mm | 12 – 25 mm | 16 – 40 mm |
| Material | SUJ2 (HRC 58-62) | SUJ2 (HRC 58-62) | SUJ2 or S45C | Bronze + PTFE composite |
| Lubrication | Requires grease | Requires grease | Requires grease | None (maintenance-free) |
| Cost Level | $ | $$ | $ | $$$ |
Step 2: Decision Tree — Do You Need Guiding Assist Pins?
Leader Pin & Bushing Pairing Guide
Every leader pin must be matched with a compatible bushing. The pairing determines alignment precision and service life.
| Leader Pin Type | Recommended Bushing | Fit Class | Notes |
|---|---|---|---|
| Straight (SUJ2) | Plain or Oil-Groove Bronze Bushing | H7/g6 | Standard pairing for 80% of molds |
| Stepped (SUJ2) | Stepped Plain Bushing | H7/g6 per step | Each step requires matched bore diameter |
| Oil-Free | Oil-Free Bushing (self-lubricating) | H7/g6 | Pair only with matching oil-free bushing |
| Guiding Assist | Ball Cage Bushing (optional) | H7/g6 | Ball cage gives max precision for assist position |
How Leader Pin Tolerance Affects Mold Alignment
Leader pin alignment precision is governed by the shaft-bore fit class. The industry standard is H7/g6 (ISO 286-1), which provides a clearance fit of 0.006 – 0.034 mm for a Ø25 mm pin. This translates to a maximum mold-half misalignment of approximately ±0.017 mm at the parting line — sufficient for most injection mold applications.
For high-precision molds (optical lenses, micro-connectors), tighter fits such as H6/g5 reduce clearance to 0.004 – 0.020 mm. However, tighter fits increase insertion force and wear rate, requiring higher-grade bushings (ball cage type) and shorter maintenance intervals.
The critical relationship is: parting line mismatch ≤ (diametral clearance / 2) + (pin straightness error) + (bore concentricity error). This means that even perfect tolerance pins will produce misalignment if the bushing bores are not concentric with the plate reference surfaces.
Selection guide: For a step-by-step approach to this decision, see our guide How to Choose the Right Leader Pin Type — Straight, Stepped, or Oil-Free.
About Leader Pins
Leader pins — also known as guide pins or mold guide pillars — are precision-hardened steel cylinders that align the mold halves during every open-close cycle. Pressed into the moving half (B-side), they slide into matched leader bushings in the fixed half (A-side), ensuring core-to-cavity alignment within 0.01 mm. We manufacture leader pins from SUJ2 bearing steel (HRC 58-62) to JIS B 5140 and DIN 9825 standards.
Frequently Asked Questions
What is the difference between straight, stepped, and oil-free leader pins?+
When should I use guiding assist pins in addition to main leader pins?+
Which leader bushing type should I pair with my leader pin?+
What tolerance grades are available for leader pins?+
What is the minimum order quantity for leader pins?+
Engineering Resources
How to Choose the Right Leader Pin Type — Straight, Stepped, or Oil-Free
Complete guide to matching leader pin geometry, material, and tolerance to your mold design requirements.
Why Mold Alignment Depends on Leader Pin Tolerance — Engineering Fundamentals
Engineering analysis of how shaft-bore fit class, straightness, and concentricity affect parting line precision.
Need Custom Leader Pins?
We manufacture precision leader pins to JIS and DIN standards. Custom dimensions available with MOQ 1 piece.