Tolerances Tables

The following tables are presented as a guide in selecting tolerances. Normally, the lower the drawing designation number, the higher the product and tooling cost. 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 to be determined upon application to rubber manufacturers.
5. Care should be taken in applying standard tolerances to products having wide sectional variations.

Table 1

Standard Dimensional Tolerance Table - Molded Solid Rubber Parts

Drawing Designation "A-1" High Precision

Drawing Designation "A1" 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.

Table 2

Standard Dimensional Tolerance Table - Molded Solid Rubber Products

Drawing Designation "A-2" Precision

Drawing Designation "A2" tolerances indicate a precision product. Molds must be precision machined and kept in good repair. While measurement methods may be simpler than with Drawing Designation "A1", careful inspection will usually be required.

Table 3

Standard Dimensional Tolerance Table - Molded Solid Rubber Products

Drawing Designation "A3" Commercial

Drawing Designation "A3" tolerances indicate a "commercial" product and will normally be used for most products.

Table 4

Standard Dimensional Tolerance Table - Molded Solid Rubber Products

Drawing Designation "A4" Non-Critical

Drawing Designation "A4" tolerances apply to products where dimensional control is non-critical and secondary to cost.