Standard Rubber Dimensional Tolerances | Molded Rubber Products 

When applying tolerances the following rules should be kept in mind.

1. Fixed dimension tolerances apply individually to each fixed dimension by its own size.
2. Closure dimension tolerances are determined by the largest closure dimension and this single tolerance is used for all other closure dimensions.
3. Fixed and closure dimensions for a given table do not necessarily go together, and can be split between tables.
4. Tolerances not shown should be determined in consultation with the rubber manufacturer.
5. Care should be taken in applying standard tolerances to products having wide sectional variations.

There are four levels of dimensional tolerances that are used for molded rubber products.

The level selected should be based upon the need with the following guidelines.

“A1” | High Precision - This is the tightest tolerance classification and indicates a high precision rubber product. Such products require expensive molds, fewer cavities per mold, costly in-process controls and inspection procedures. It is desirable that the exact method of measurement be agreed upon between rubber manufacturer and customer, as errors in measurement may be large in relation to the tolerance. Some materials, particularly those requiring post curing, do not lend themselves to Drawing Designation “A1” tolerances.

“A2” |​ Precision - These tolerances indicate a precision product. Molds must be precision machined and kept in good repair. While measurement methods may be simpler than the Drawing Designation “A1”, careful inspection will usually be required.

“A3” |​ Commercial (table) - These tolerances indicate a “commercial” product and will normally be used for most products.

“A4” |​ Basic - These tolerances apply to products where some dimensional control is required but is secondary to cost.