Reading the Fine Print on Base Tolerances
What standards cover
Base standards typically define plate thickness tolerances, parallelism between faces, locating dimensions, guide hole positions and fit classes for pillars and bushings. A conforming base gives you a geometrically sound skeleton — plates that sit flat and align predictably.
This is why standard bases interchange between machines and mold makers: everyone builds on the same geometry.
What they don't cover
Cavity pocket positions and depths, cooling circuit geometry, surface finish on machined pockets, special ejector patterns and any features the molder adds — these fall outside the base standard and are the mold maker's responsibility to specify and execute.
Confusing the two leads to disputes: the base supplier meets the standard while the finished mold still needs the maker's precision on custom features.
Where to tighten deliberately
Most applications are served by standard tolerance classes. Tighten only where it matters: high-cavitation family molds with shared inserts, thin-wall tools needing exceptional parallelism, or molds with interchangeable units — and accept the price of that tightening consciously.
FAQ
Do mold base standards guarantee parallel plates?
Within the stated tolerance class, yes — parallelism is a defined property; check the class against your mold's needs.
Are standard bases interchangeable?
Within the same standard and size series, largely yes — a major benefit for repairs and plate replacement.
Who is responsible for pocket accuracy?
The mold maker machining the pockets — base standards cover the base, not added features.
When do I need a tighter tolerance class?
High-cavitation, thin-wall or interchangeable-unit molds justify tighter parallelism and locating tolerances; standard classes suit most other work.
All figures above refer to standard product data sheets; final confirmation is subject to written quotation.