RMA Precision Tolerance

The Rubber Manufacturers Association (RMA) has developed tolerance tables with ranges to provide communication between users and providers across a wide range of industries. The data are very essential when designing any product part.

Metric Tolerances (mm)

NOMINAL DIMENSION A1 A2 A3 A4
ABOVE UP TO AND INCLUDING FIXED CLOSURE FIXED CLOSURE FIXED CLOSURE FIXED CLOSURE
0 10 0.1 0.13 0.16 0.2 0.2 0.32 0.32 0.8
10 16 0.13 0.16 0.2 0.25 0.25 0.4 0.4 0.9
16 25 0.16 0.2 0.2 0.32 0.32 0.5 0.5 1
25 40 0.2 0.25 0.32 0.4 0.4 0.63 0.63 1.12
40 63 0.25 0.32 0.4 0.5 0.5 0.8 0.8 1.25
63 100 0.32 0.4 0.5 0.63 0.63 1 1.1 1.4
100 160 0.4 0.5 0.63 0.8 0.8 1.25 1.25 1.6
160 & Over (Multiply by) x .004 x .005 x .005 x .008 x .008 x .010

Inch Tolerances (in)

NOMINAL DIMENSION A1 A2 A3 A4
ABOVE UP TO AND INCLUDING FIXED CLOSURE FIXED CLOSURE FIXED CLOSURE FIXED CLOSURE
0 0.40 0.004 0.005 0.006 0.008 0.008 0.013 0.013 0.032
0.40 0.63 0.005 0.006 0.008 0.010 0.010 0.016 0.016 0.036
0.63 1.00 0.006 0.006 0.010 0.013 0.013 0.020 0.020 0.040
1.00 1.60 0.008 0.010 0.013 0.016 0.016 0.025 0.025 0.045
1.60 2.50 0.010 0.013 0.016 0.020 0.020 0.032 0.032 0.050
2.50 4.00 0.013 0.016 0.020 0.025 0.025 0.040 0.040 0.056
4.00 6.30 0.016 0.020 0.025 0.032 0.032 0.050 0.050 0.063
6.30 & Over (Multiply by) x .004 x .005 x .005 x .008 x .008 x .010

Table 12. Summary of RMA Drawing Designations Extruded Rubber Products

RMA CLASS DIMENSIONAL TOLERANCE*TABLE 13 CUTLENGTH TOLERANCE*TABLE 16 SPLICEDLENGTH TOLERANCE*TABLE 16 MANDRELCURED* TABLE 20
1 E1 L1 S1 EN1
2 E2 L2 S2 EN2
3 E3 L3 S3 EN3
4 - - - -

Table 13. Standard Cross-Sectional Tolerance

RMA CLASS 1 - HIGH PRECISION 2 - PRECISION 3 - COMMERCIAL
DRAWING DESIGNATION E1 E2 E3
DIMENSIONS (In Millimeters)
Above Up to and Including ±0.15 ±0.25 ±0.40
0 1.5 0.20 0.35 0.50
1.5 2.5 0.25 0.40 0.70
2.5 4.0 0.35 0.50 0.80
4.0 6.3 0.40 0.70 1.00
6.3 10 0.50 0.80 1.30
10 16 0.70 1.00 1.60
16 25 0.80 1.30 2.00
25 40 1.00 1.60 2.50
40 63 1.30 2.00 3.20
63 100
RMA CLASS 1 - HIGH PRECISION 2 - PRECISION 3 - COMMERCIAL
DRAWING DESIGNATION E1 E2 E3
DIMENSIONS (In Inches)
Above Up to and Including ±0.006 ±0.010 ±0.015
0 0.06 0.008 0.014 0.020
0.06 0.10 0.010 0.016 0.027
0.10 0.16 0.014 0.020 0.031
0.16 0.25 0.016 0.027 0.039
0.25 0.39 0.020 0.031 0.051
0.39 0.63 0.027 0.039 0.063
0.63 0.98 0.031 0.051 0.079
0.98 1.57 0.039 0.063 0.098
1.57 2.48 0.051 0.079 0.126
2.48 3.94

Table 16. Cut Length tolerance for unspliced extrusion

RMA CLASS 1 - HIGH PRECISION 2 - PRECISION 3 - COMMERCIAL
DRAWING DESIGNATION L1 L2 L3
DIMENSIONS (In Millimeters)
Above Up to and Including ±0.7 ±0.04 ±1.6
0 40 0.08 1.3 2.0
40 63 1.0 1.6 2.5
63 100 1.3 2.0 3.2
100 160 1.6 2.5 4.0
160 250 2.0 3.2 5.0
250 400 2.5 4.0 6.3
400 630 3.2 5.0 10.0
630 1000 4.0 6.3 12.5
1000 1600 5.0 10.0 16.0
1600 2500 6.3 12.5 20.0
2500 4000 0.16% 0.32% 0.50%
4000
DIMENSIONS (In Inches)
Above Up to and Including ±0.03 ±0.04 ±0.06
0 1.6 0.03 0.05 0.8
1.6 2.5 0.04 0.06 0.10
2.5 4.0 0.05 0.8 0.13
4.0 6.3 0.06 0.10 0.16
6.3 10.0 0.8 0.13 0.20
10.0 16.0 0.10 0.16 0.25
16.0 25.0 0.13 0.20 0.40
25.0 40.0 0.16 0.25 0.50
40.0 63.0 0.20 0.40 0.63
63.0 100.0 0.25 0.50 0.80
100.0 160.0 0.16% 0.32% 0.50%
160.0

Table 18. Spliced Length Tolerances

RMA CLASS 1 - HIGH PRECISION 2 - PRECISION 3 - COMMERCIAL
DRAWING DESIGNATION S1 S2 S3
DIMENSIONS (In Millimeters)
Above Up to and Including ±302 ±3.2 ±7.1
0 250 4.0 7.1 8.0
250 400 5.0 8.0 9.0
400 630 6.3 9.0 10.0
1000 1600 8.0 10.0 11.2
1600 2500 10.0 11.2 12.3
2500 over 12.5 12.5 16.0
DIMENSIONS (In Inches)
Above Up to and Including ±.13 ±.25 ±.28
0 10 .16 .28 .32
10 16 .20 .32 .36
16 25 .25 .36 .40
25 40 .32 .40 .45
40 63 .40 .45 .50
63 100 .50 .50 .53
100 over

Table 20. Tolerances on Internal Dimensions of Mandrel-Supported Extrusions

RMA CLASS 1 - HIGH PRECISION 2 - COMMERCIAL 3 - NON-CRITICAL
DRAWING DESIGNATION EN1 EN2 EN3
NOMINAL DIMENSIONS (In Millimeters)
Above Up to and Including ±0.20 ±0.20 ±0.35
0 4 0.20 0.25 0.40
4 6.3 0.25 0.35 0.50
6.3 10 0.35 0.40 0.70
10 16 0.40 0.50 0.80
16 25 0.50 0.70 1.00
25 40 0.70 0.80 1.30
40 63 0.80 1.00 1.60
63 100 1.00 1.30 2.00
100 160 0.6% 0.8% 1.2%
160
NOMINAL DIMENSIONS (In Inches)
Above Up to and Including ±0.008 ±0.08 ±0.014
0 0.16 0.008 0.010 0.016
0.16 0.25 0.010 0.014 0.020
0.25 0.40 0.014 0.016 0.028
0.40 0.63 0.016 0.020 0.032
0.63 1.00 0.020 0.028 0.040
1.00 1.60 0.028 0.032 0.051
1.60 2.50 0.032 0.040 0.063
2.50 4.00 0.040 0.051 0.079
4.00 6.30 0.6% 0.8% 1.2%
6.30
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