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RMA Tolerances

Helpful guides for designing a part

Rubber Manufacturers Association (RMA) tolerances are based on industry standards for various types of manufacturing processes.

RMA Table 3 – Molded A2 Precision

Standard Dimensional Tolerance Table–Molded Rubber Products
Drawing Designation “A2” Precision




RMA Table 13 – Dense Cross-Section Organic/Silicone Class 2 Precision

Standards For Cross-Sectional Tolerance Table

Note: Tolerances On Dimensions To The Left 100mm (3.94 In.) Should Be Agreed Upon By Supplier And User. General Cross-Sectional Dimensions Below 1mm (0.04 In.) Are Impractical. In General, Softer Materials And Those Requiring A Post-Cure Need Greater Tolerances.

RMA Table 16 – Dense Cut Length L2 Commercial

Cut Length Tolerance Tables For Unspliced Extrusion

Note: Special Consideration Of Tolerances Will Have To Be Given To Both Extremely Soft And High Tensile Stocks.





RMA Table 35 – Length and Width Die Cut Sponge #2,

Tolerances On Left And Width Dimensions Of Die-Cut Sheet Or Strip, Expanded, Closed-Cellular Rubber.

* Separate schedules of length and width tolerances are listed for different thickness of these materials because of the “dish” effect in die-cutting. This is more noticeable as the thickness increases. As shown in the drawing below, the “dish” effect is a concavity of die-cut edges (due to the squeezing of the material by the pressure of the cutting die).

The width “W” (or length) at the top and bottom surface are slightly greater than the width “W-X” at the center.

Note: Class 1 tolerances should not be applied to the softer grades of material, below 63 kPa (9 psi)

RMA Table 36 – Sponge Cross Section Organic/Silicone #1, BEC 1

Tolerances On Cross-Sectional Dimensions Of Irregular And Cored Shapes Of Extruded, Expanded, Closed-Cellular Rubber. Class 1 Tolerances In The Table To The Right Are Recommended Only For High Volume, Tight Products Automotive Applications.

*Class 1 Tolerances Should Not Be Applied To Softer Grades Of Material – Below 63 KPa (9 Psi) Compression Deflection.





RMA Table 38 – Cut Length #1, BEL 1

Tolerances On Cut Lengths Of All Extruded, Expanded, Closed-Cellular Rubber Products.

* Class 1 tolerances should not be applied to the softer grades of materials–below 63 kPa (9psi) compression deflection.

** Accurate measurement of long lengths is difficult because these materials stretch or compress easily. Where close tolerances are required on long lengths, a specific technique of measurement should be agreed upon between purchaser and manufacturer.

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