RMA Tolerances

Helpful guides for designing a part

Selecting the right seal or gasket for a specific application involves knowing the answers to many questions about what your requirements might be. To help you in this process, the following tables are available for you.

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RMA tolerance tables

RMA Table 3 - Molded A2 Precision

standard dimensional tolerance table--molded rubber products
drawing designation "a2" precision

Size (Millimeters) Fixed Closure Size (Inches) Fixed Closure
Above - Including     Above - Including    
0 - 10 ±0.16 ±0.20 0 - 0.40 ±0.0006 ±0.0008
10 - 16 0.20 0.25 0.40 - 0.63 0.008 0.010
16 - 25 0.25 0.32 0.63 -1.00 0.010 0.013
25 - 40 0.32 0.40 1.00 - 1.60 0.013 0.016
40 - 63 0.40 0.50 1.60 - 2.50 0.016 0.020
63-100 0.50 0.63 2.50 - 4.00 0.020 0.025
100 - 160 0.63 0.80 4.00 - 6.30 0.025 0.032
160 - & over     6.30 - & over    
multiply by 0.004 0.005 multiply by 0.004 0.005

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

standards for cross-sectional tolerance table
note: tolerances on dimensions above 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 Class 1
High Precision 		2
Precision 		3
Commercial
Drawing Designation E1 E2 E3
Dimensions (mm)
Above Up To
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 0.40 0.70 1.00
10 16 0.50 0.80 1.30
16 25 0.70 1.00 1.60
25 40 0.80 1.30 2.00
40 63 1.00 1.60 2.50
63 100 1.30 2.00 3.20

RMA Class RMA Class
1
High Precision
2
Precision 		3
Commercial
Drawing Designation
 E1 E2 E3
Dimensions (in)
  
Above
Up to
0
0.06
+/- 0.006
+/- 0.010
+/- 0.015
0.06
0.10
0.008
0.014
0.020
0.10
0.16
0.010
0.016
0.027
0.16
0.25
0.014
0.020
0.031
0.25
0.39
0.016
0.027
0.039
0.39
0.63
0.020
0.031
0.051
0.63
0.98
0.027
0.039
0.063
0.98
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

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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 Class
1
Precision
2
Commercial
3
Non-Critical
Drawing Designation L1 L2 L3
Length (mm)
Above Up to
0
40
+/- 0.7
+/- 1.0
+/- 1.6
40
63
0.8
1.3
2.0
63
100
1.0
1.6
2.5
100
160
1.3
2.0
3.2
160
250
1.6
2.5
4.0
250
400
2.0
3.2
5.0
400
630
2.5
4.0
6.3
630
1000
3.2
5.0
10.0
1000
1600
4.0
6.3
12.5
1600
2500
5.0
10.0
16.0
2500
4000
6.3
12.5
20.0
4000
0.16%
0.32%
0.50%

Drawing Designation      
Length (in)  
Above
Up to
0
1.6
 +/- 0.03
+/- 0.04
+/- 0.06
1.6
2.5
 0.03
0.05
0.08
2.5
4.0
0.04
0.06
0.10
4.0
6.3
0.05
0.08
0.13
6.3
10.0
0.06
0.10
0.16
10.0
16.0
0.08
0.13
0.20
16.0
25.0
0.10
0.16
0.25
25.0
40.0
0.13
0.20
0.40
40.0
63.0
0.16
0.25
0.50
63.0
100.0
0.20
0.40
0.63
100.0
160.0
0.25
0.50
0.80
160.0
0.16%
0.32%
0.50%

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RMA Table 35 - Length and Width Die Cut Sponge #2, BL2

Tolerances on left and width dimensions of die-cut sheet or strip, expanded, closed-cellular rubber.

RMA Class
1
2
3
RMA Drawing Designation
BL1
BL2
BL3
Millimeters
Tolerance
For thickness up to 6.3mm*
under 25
+/- 0.63
+/- 0.80
+/- 1.0
25 to 160
0.80
1.0
1.25
over 160 multiply by
0.0063
0.01
0.016
For thickness over 6.3 to 12.5mm*
under 25
+/- 0.81
+/- 1.0
+/- 1.25
25 to 160
1.0
1.25
1.6
over 160 multiply by
0.0063
0.01
0.016
For thickness over 12.5mm*
under 25
+/- 1.0
+/- 1.25
+/- 1.6
25 to 160
1.25
1.6
2.0
over 160 multiply by
0.0063
0.01
0.016

Inches
Tolerance
For thickness up to .25in*
under 1.0
+/- .025
+/- .032
+/- .040
1.0 to 6.3
.032
.040
.050
over 6.3 multiply by
0.0063
0.010
0.016
For thickness over .25 to .50in*
under 1.0
+/- .032
+/- .040
+/- .050
1.0 to 6.3
.040
.050
.063
over 6.3 multiply by
0.0063
0.010
0.016
For thickness over .50in*
under 1.0
+/- .040
+/- .050
+/- .063
1.0 to 6.3
.050
.063
.080
over 6.3 multiply by
0.0063
0.010
0.016

* 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)

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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 below are recommended only for high volume, tight products automotive applications.

RMA Class
1*
2
3
RMA Drawing Designation
BEC1
BEC2
BEC3
Millimeters
Tolerance
Above
Up to
0
6.3
+/- 0.4
+/- 0.5
+/- 0.63
6.3
12.5
.063
1.0
1.25
12.5
25.0
1.25
2.0
2.5
25.0
40.0
2.0
3.2
4.0
40.0 & over multiply by
0.06
0.08
0.10

Inches
Tolerance
Above
Up to
0
.25
+/- .016
+/- 0.20
+/- .025
.25
.50
.025
.040
.050
.50
1.0
.050
.080
.100
1.0
1.6
.080
.125
.160
1.6 & over multiply by
0.060
0.080
0.100

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

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RMA Table 38 - Cut Length #1, BEL 1

Tolerances on cut lengths of all extruded, expanded, closed-cellular rubber products.

RMA Class
1*
2
3
RMA Drawing Designation
BEL1
BEL2
BEL3
Millimeters
Tolerance
Above
Including
0
80
+/- 1.6
+/- 1.6
+/- 3.2
80
160
3.2
3.2
6.3
160
315
6.3
6.3
12.5
315
630**
multiply by .02
12.5
25.0
630
1250**
multiply by .02
25.0
50.0
1250 &over multiply by
0.02
0.03
.040

RMA Class
1
2
3
RMA Drawing Designation
BEL1
BEL2
BEL3
Inches
Tolerance
Above
Including
0
3.15
+/- .063
+/- .063
+/- .125
3.15
6.3
.125
.125
.250
6.3
12.5
.250
.250
.500
12.5
25**
multiply by .02
.500
1.000
24.0
50**
multiply by .02
1.000
2.000
50.0 & over multiply by
0.02
0.030
0.040

* 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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