Rubber Products: All About Tolerances

Unlike parts produced from solid materials such as steel or hard plastics, rubber products that are cut from sheet are not capable of supporting the same level of dimensional tolerances in production. As a material, rubber compounds are subject to many variables that can affect the final dimensions of the finished part.

For rubber products cut from rubber sheet or strip, dimensional tolerances are a primary consideration in the manufacturing process. The Rubber Manufacturers Association (RMA) has developed and published in the RMA Rubber Handbook tolerance tables with ranges to facilitate communication between suppliers and customers across a wide range of industries. These tolerance designations relate to the variability inherent in processing rubber products and parts.

RMA Commercial Gauge Tolerances

Determining tolerances for flexible rubber products such as gaskets and seals can be tricky because these products are designed to flex, and expand and contract. In manufacturing cut rubber products and parts, Canada Rubber Group Inc. (CRGI) uses RMA commercial gauge tolerances in our production process. These tolerances apply to products and parts cut from rubber sheet and diaphragm sheet, as well as closed and open cell foams and sponges.

An excerpt of the RMA commercial gauge tolerances that CRGI uses in part production is shown in the table below. The table is separated by nominal thickness because rubber materials are often deformed (or “dished) when cutting.

As noted above, in producing cut rubber products and parts, many factors can cause variation in the finished part size. Material age and cure time, storage and processing temperature, and pressure imposed on the material as it is being cut can all affect the final dimensions. When ordering cut rubber products, it is therefore unrealistic to expect the same precision of tolerances that are achievable when machining solid metals such as steel or aluminum. When specifying desired tolerances, design engineers and buyers should take care to refer to the published RMA gauge tolerances which are followed by most manufacturers in the industry.

In addition to commercial gauge tolerances, the RMA also publishes tolerances for molded and extruded rubber products. These tables should be consulted when ordering parts that require either molding or extrusion in their manufacture.

For further information on tolerances for rubber products which we supply, please contact our sales department at