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) Fixed Closure Size (inches) Fixed Closure
Over Through Over Through
0 10 ±0.10 ±0.10 0.000 0.400 ±0.004 ±0.005
10 16 0.13 0.16 0.400 0.630 0.005 0.006
16 25 0.16 0.20 0.630 1.000 0.006 0.008
25 40 0.20 0.25 1.000 1.600 0.008 0.010
40 63 0.25 0.32 1.600 2.500 0.010 0.013
63 100 0.32 0.40 2.500 4.000 0.013 0.016
100 160 0.40 0.50 4.000 6.300 0.016 0.020

 

A2 Precision

Size (mm) Fixed Closure Size (inches) Fixed Closure
Over Through Over Through
0 10 ±0.16 ±0.10 0.000 0.400 ±0.006 ±0.008
10 16 0.20 0.16 0.400 0.630 0.008 0.010
16 25 0.25 0.20 0.630 1.000 0.010 0.013
25 40 0.32 0.25 1.000 1.600 0.013 0.016
40 63 0.40 0.32 1.600 2.500 0.016 0.020
63 100 0.50 0.40 2.500 4.000 0.020 0.025
100 160 0.63 0.50 4.000 6.300 0.025 0.032
160 & over multiply by 0.004 0.005 6.300 & over
multiply by
0.004 0.005

 

A3 Commercial

Size (mm) Fixed Closure Size (inches) Fixed Closure
Over Through Over Through
0 10 ±0.20 ±0.32 0.000 0.400 ±0.008 ±0.013
10 16 0.25 0.40 0.400 0.630 0.010 0.016
16 25 0.32 0.50 0.630 1.000 0.013 0.020
25 40 0.40 0.63 1.000 1.600 0.016 0.025
40 63 0.50 0.80 1.600 2.500 0.020 0.032
63 100 0.63 1.00 2.500 4.000 0.025 0.040
100 160 0.80 1.25 4.000 6.300 0.032 0.050
160 & over multiply by 0.005 0.008 6.300 & over
multiply by
0.005 0.008

 

A4 Basic

Size (mm) Fixed Closure Size (inches) Fixed Closure
Over Through Over Through
0 10 ±0.32 ±0.80 0.000 0.400 ±0.013 ±0.032
10 16 0.40 0.90 0.400 0.630 0.016 0.036
16 25 0.50 1.00 0.630 1.000 0.020 0.040
25 40 0.63 1.12 1.000 1.600 0.025 0.045
40 63 0.80 1.25 1.600 2.500 0.032 0.050
63 100 1.00 1.40 2.500 4.000 0.040 0.056
100 160 1.25 1.60 4.000 6.300 0.050 0.063
160 & over multiply by 0.008 0.010 6.300 & over
multiply by
0.008 0.010

 

 

 

 

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 Class High Precision Precision Commercial
Drawing Designation E1 E2 E3
Dimensions (millimeters)      
Over Through
0.0 1.5 ±0.15 ±0.25 ±0.40
1.5 2.5 0.20 0.35 0.50
2.5 4.0 0.25 0.40 0.70
4.0 6.3 0.35 0.50 0.80
6.3 10.0 0.40 0.70 1.00
10.0 16.0 0.50 0.80 1.30
16.0 25.0 0.70 1.00 1.60
25.0 40.0 0.80 1.30 2.00
40.0 63.0 1.00 1.60 2.50
63.0 100.0 1.30 2.00 3.20
APRM Class High Precision Precision Commercial
Drawing Designation E1 E2 E3
Dimensions (inches)      
Over Through
0.000 0.060 ±0.006 ±0.010 ±0.015
0.600 0.100 0.008 0.014 0.020
0.100 0.160 0.010 0.016 0.027
0.160 0.250 0.014 0.020 0.031
0.250 0.390 0.016 0.027 0.039
0.390 0.630 0.020 0.031 0.051
0.630 0.980 0.027 0.039 0.063
0.980 1.570 0.031 0.051 0.079
1.570 2.480 0.039 0.063 0.098
2.480 3.940 0.051 0.079 0.126

 

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.