Common Fits and Tolerances in Injection Mold Assembly Drawings
1. What Are Fits and Tolerances?
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Tolerance refers to the allowable dimensional variation of a part.
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Fit describes how two mating parts relate in size:
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Clearance Fit: Always has space; allows movement.
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Transition Fit: Close fit; may allow easy assembly/disassembly.
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Interference Fit: Tightly joined; parts are pressed together.
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2. Common Fit Applications in Mold Assembly
| Mold Component | Fit Type | Recommended Fit | Purpose |
|---|---|---|---|
| Guide Pins & Bushes | Clearance Fit | H7/g6 or H7/f7 | Smooth sliding |
| Inserts & Mold Base | Interference Fit | H6/p6 or H7/n6 | Firm fixing |
| Core & Mold Plate | Transition Fit | H7/k6 | Accurate location, removable |
| Dowel Pins | Transition Fit | h6/H7 | Removable yet precise positioning |
3. Standards We Follow
We commonly follow:
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ISO 286 Fit System
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GB/T 1800 Chinese Standard
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Customer-specific standards (e.g., ANSI, JIS)
4. Why Tolerances Matter
✔️ Prevents flash, shrinkage, and mismatched cavities
✔️ Increases mold longevity and reduces wear
✔️ Improves CNC machining consistency
✔️ Saves time on assembly and maintenance
5. Our Expertise
We specialize in: ✅ Tight-tolerance machining
✅ Fit optimization based on structure and use
✅ Full technical support during mold design and assembly
Feel free to contact us for advice on selecting the right fit and tolerance for your custom projects.
