The Rubber Manufacturers Association (RMA), now known as the US Tire Manufacturer’s Association has published the RMA handbook. The purpose of this handbook is to provide a method for standardizing design requirements for molded rubber products.

The information included in the RMA handbook will give an overview of what to expect with dimension tolerances and will let customers know more about the manufacturing process. Design engineers should find the handbook quite helpful in creating a product that works great for the intended application.

In designing rubber parts, engineers have always had the problem of specifying requirements in terms sufficiently clear to enable the manufacturers to determine with a reasonable degree of accuracy what is actually described in terms of performance, tolerance and service characteristics. At Vip Rubber & Plastic, we can make almost any custom product, but we need to understand exactly what you are trying to make and how that product should perform.

The use of this handbook will help us understand your manufacturing goals, production needs, quality requirements and gives us each a template to follow so everyone is on the same page. We have a long history of manufacturing molded parts, as well as hundreds of custom extruded rubber profiles , rubber sheet, plastic pipe and tubing, extruded plastic.

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RMA Handbook

Dimensional tolerances, or part tolerances, are acceptable variations in part size. These differences are caused by slight manufacturing variations and expressed as plus or minus (±) amounts in millimeters (mm) or inches (in). Precision parts such as aerospace components require tighter tolerances with less variation. Other types of components, such as consumer products, may allow for greater part-to-part differences.

The Rubber Handbook, a publication from the Association for Rubber Products Manufacturers (ARPM), provides part tolerances for molded and extruded rubber products. Often, this publication is called the RMA Handbook because the ARPM was originally known as the Rubber Manufacturers Association (RMA) before a name change to the U.S. Tire Manufacturers Association.

How to Use the RMA Handbook

VIP Rubber and Plastic uses the contents of the RMA Handbook contents to communicate with our customers in a standardized way. The Handbook contains separate chapters for molded and extruded parts, and each chapter contains numbered tables. These tolerance tables, as they’re known, contain allowable part tolerances. They also drawing designations that indicate the level of precision.

The RMA Handbook isn’t free to download, but VIP Rubber and Plastic can share some of its contents with you as we work together on your project. Because the drawings you send to us need to reference RMA information, you’ll find the most important tolerance tables listed below. If you’ve never worked with rubber products before, please note these tolerances are different than with metal products.

Molded Rubber Products      

There are four ARPM drawing designations for the dimensional tolerances of molded rubber products

  • A1 – High Precision
  • A2 – Precision
  • A3 – Commercial
  • A4 – Basic

You’ll find these tolerances below so that you can add them to the part drawings that you send to us.

A1 High Precision

Size (mm)FixedClosureSize (inches)FixedClosure
OverThroughOverThrough
010±0.10±0.100.0000.400±0.004±0.005
10160.130.160.4000.6300.0050.006
16250.160.200.6301.0000.0060.008
25400.200.251.0001.6000.0080.010
40630.250.321.6002.5000.0100.013
631000.320.402.5004.0000.0130.016
1001600.400.504.0006.3000.0160.020

 

A2 Precision

Size (mm)FixedClosureSize (inches)FixedClosure
OverThroughOverThrough
010±0.16±0.100.0000.400±0.006±0.008
10160.200.160.4000.6300.0080.010
16250.250.200.6301.0000.0100.013
25400.320.251.0001.6000.0130.016
40630.400.321.6002.5000.0160.020
631000.500.402.5004.0000.0200.025
1001600.630.504.0006.3000.0250.032
160& over multiply by0.0040.0056.300& over
multiply by
0.0040.005

 

A3 Commercial

Size (mm)FixedClosureSize (inches)FixedClosure
OverThroughOverThrough
010±0.20±0.320.0000.400±0.008±0.013
10160.250.400.4000.6300.0100.016
16250.320.500.6301.0000.0130.020
25400.400.631.0001.6000.0160.025
40630.500.801.6002.5000.0200.032
631000.631.002.5004.0000.0250.040
1001600.801.254.0006.3000.0320.050
160& over multiply by0.0050.0086.300& over
multiply by
0.0050.008

 

A4 Basic

Size (mm)FixedClosureSize (inches)FixedClosure
OverThroughOverThrough
010±0.32±0.800.0000.400±0.013±0.032
10160.400.900.4000.6300.0160.036
16250.501.000.6301.0000.0200.040
25400.631.121.0001.6000.0250.045
40630.801.251.6002.5000.0320.050
631001.001.402.5004.0000.0400.056
1001601.251.604.0006.3000.0500.063
160& over multiply by0.0080.0106.300& over
multiply by
0.0080.010

 

 

 

 

Extruded Rubber Products     

There are four ARPM drawing designations for the dimensional tolerances of extruded rubber products

  • E1 – High Precision
  • E2 – Precision
  • E3 – Commercial

You’ll find these tolerances below so that you can add them to the part drawings you send to us.

APRM ClassHigh PrecisionPrecisionCommercial
Drawing DesignationE1E2E3
Dimensions (millimeters)   
OverThrough
0.01.5±0.15±0.25±0.40
1.52.50.200.350.50
2.54.00.250.400.70
4.06.30.350.500.80
6.310.00.400.701.00
10.016.00.500.801.30
16.025.00.701.001.60
25.040.00.801.302.00
40.063.01.001.602.50
63.0100.01.302.003.20
APRM ClassHigh PrecisionPrecisionCommercial
Drawing DesignationE1E2E3
Dimensions (inches)   
OverThrough
0.0000.060±0.006±0.010±0.015
0.6000.1000.0080.0140.020
0.1000.1600.0100.0160.027
0.1600.2500.0140.0200.031
0.2500.3900.0160.0270.039
0.3900.6300.0200.0310.051
0.6300.9800.0270.0390.063
0.9801.5700.0310.0510.079
1.5702.4800.0390.0630.098
2.4803.9400.0510.0790.126

 

These aren’t the only tables in the RMA Handbook – and there are additional chapters besides molded and extruded rubber products. There are also notes, explanations, and other information that product designers may need to consider, so contact us if you have questions about rubber manufacturing. We work with a variety of rubber materials and all of our products are proudly Made in the USA.