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RMA Tolerances

Standard Cross-Sectional Tolerances

For outside diameters, Inside Diameters, Wall, width, Height and general cross-sectional dimensions of extrusions

RMA Class 1 2 3
High Precision Precision Precision
RMA Drawing designation E1 E2 E3
Dimension (in mm)
Above – Up to +/- +/- +/-
0 – 1.5 0.15 0.25 0.4
1.5 – 2.5 0.2 0.35 0.5
2.5 – 4.0 0.25 0.4 0.7
4.0 – 6.3 0.35 0.5 0.8
6.3 – 10 0.4 0.7 1
10 – 16 0.5 0.8 1.3
16 – 25 0.7 1 1.6
25 – 40 0.8 1.3 2
40 – 63 1 1.6 2.5
63 – 100 1.3 2 3.2
RMA Class 1 2 3
High Precision Precision Precision
RMA Drawing designation E1 E2 E3
Dimension (in Inches)
Above – Up to +/- +/- +/-
0 – 06 0.006 0.01 0.015
06 – 10 0.008 0.014 0.02
10 – 16 0.01 0.016 0.027
16 – 25 0.014 0.02 0.031
25 – 39 0.016 0.027 0.039
39 – 63 0.02 0.031 0.051
63 – 98 0.027 0.039 0.063
98 – 1.57 0.031 0.051 0.079
1.57 – 2.48 0.039 0.063 0.098
2.48 – 3.94 0.051 0.079 0.126

Note: Tolerances on Dimensions above 100mm (3.94) should be agreed upon by the supplier and user. General cross-sectional dimensions below 1mm (0.04) are impractical. In general, softer materials and those requiring a post-cure need greater tolerance.

RMA Standard Dimensional Tolerance Table for Molded Rubber Products

The following tables are presented as a guide to 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 on its own
  2. The largest closure dimension determines closure dimension tolerances and this single tolerance is used for all other closure
  3. Fixed and closure dimensions for a given table do not necessarily go together and can be split between
  4. Tolerances not shown to be determined upon application to rubber
  5. Care should be taken in applying standard tolerances to products having wide sectional variations.
Table #1

Standard Dimensional Tolerance Table – Molded Solid Rubber Products

Drawing Designation “A-1” High Precision

Size (millimetres) Fixed Closure Size (Inches) Fixed Closure
Above – Incl. +/- .10 +/- .13 Above – Incl. +/- .004 +/- .005
0 – 10 0 – .40
10 – 16 0.13 0.16 .40 – .63 0.005 0.006
16 – 25 0.16 0.2 .63 – 1.00 0.006 0.008
25 – 40 0.2 0.25 1.00 – 1.60 0.008 0.01
40 – 63 0.25 0.32 1.60 – 2.50 0.01 0.013
63 – 100 0.32 0.4 2.50 – 4.00 0.013 0.016
100 – 160 0.4 0.5 4.00 – 6.30 0.016 0.02

Drawing Designation “A1” is the tightest tolerance classification and indicates a high-precision rubber product. Such products require expensive moulds, fewer cavities per mould, costly in-process controls and inspection procedures. It is desirable that the exact method of measurement be agreed upon between the 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”

Table #2

Standard Dimensional Tolerance Table – Molded Solid Rubber Products

Drawing Designation “A-2” Precision

Size (millimetres) Fixed Closure Size (inches) Fixed Closure
Above – Incl. +/-.16 +/- .20 Above – Incl. +/• .006 +/- .008
0 – 10 0.2 0.25 0 – .40 0.008 0.01
10 – 16 0.25 0.32 .40 – 63 0.01 0.013
16 – 25 0.32 0.4 .63 – 1.00 0.013 0.016
25 – 40 0.4 0.5 1.00 – 1.60 0.016 0.02
40 – 63 0.5 0.63 1.60 – 2.50 0.02 0.025
63 – 100 0.63 0.8 2.50 – 4.00 0.025 0.032
100 – 160 0.005 0.006 4.00 – 6.30 0.005 0.006
160 & over 6.30 & over
multiply by multiply by

Drawing Designation “A2” tolerances indicate a precision 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

Size (millimetres) Fixed Closure Size (inches) Fixed Closure
Above – Incl. +/- .20 +/- .32 Above – Incl. +/- .008 +/- .013
0 – 10 0.25 0.4 0 – .40 0.01 0.016
10 – 16 0.32 0.5 .40 – 63 0.013 0.02
16 – 25 0.4 0.63 .63 – 1.00 0.016 0.025
25 – 40 0.5 0.8 1.00 – 1.60 0.02 0.032
40 – 63 0.63 1 1.60 – 2.50 0.025 0.04
63 – 100 0.8 1.25 2.50 – 4.00 0.032 0.05
100 – 160 0.006 0.009 4.00 – 6.30 0.006 0.009
160 & over 6.30 & over
multiply by multiply by

Drawing Designation “A3” tolerances indicate a “commercial” product and will normally be used for most Produce

Table #4

Standard Dimensional Tolerance Table – Molded Solid Rubber Products

Drawing Designation “A4” Non-Critical

Size (millimetres) Fixed Closure Size (inches) Fixed Closure
Above – Incl. +/- .32 +/- .80 Above – Incl. +/- .013 +/- .032
0 – 10 0.4 0.9 0 – .40 0.016 0.036
10 – 16 0.5 1 .40 – 63 0.02 0.04
16 – 25 0.63 1.12 .63 – 1.00 0.025 0.045
25 – 40 0.8 1.25 1.00 – 1.60 0.032 0.05
40 – 63 1 1.4 1.60 – 2.50 0.04 0.056
63 – 100 1.25 1.6 2.50 – 4.00 0.05 0.063
100 – 160 0.008 0.01 4.00 – 6.30 0.008 0.01
160 & over 6.30 & over
multiply by multiply by
Drawing Designation “A4” tolerances apply to products where dimensional control is non-critical and secondary to cost.