RMA Tolerances Tables

The Rubber Manufacturers Association (RMA) has developed tolerance tables with ranges to provide communication between user and provider across a wide range of industries. These are helpful when designing and producing a part. You can also consult the RMA article on factors affecting tolerances of molded rubber products.   

 

• RMA Factors affecting tolerances
• RMA Molded Tolerances

• Metric Tolerances (mm)
• Inch Tolerances (in)

• RMA Extrusion Tolerances

• Table 12.
  Summary of RMA Drawing Designations Extruded Rubber Products
• Table 13.
  Standard Cross-Sectional Tolerance
• Table 16.
  Cut Length tolerance for unspliced extrusion
• Table 18.
  Spliced Length Tolerances
• Table 20.
  Tolerances on Internal Dimensions of Mandrel-Supported Extrusions

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 0 1.5 1.5 2.5 2.5 4.0 4.0 6.3 6.3 10 10 16 16 25 25 40 40 63 63 100	+0.15 +0.25 +0.40 0.20 0.35 0.50 0.25 0.40 0.70 0.35 0.50 0.80 0.40 0.70 1.00 0.50 0.80 1.30 0.70 1.00 1.60 0.80 1.30 2.00 1.00 1.60 2.50 1.30 2.00 3.20
RMA Class	1 - High Precision 2 - Precision 3 - Commercial
Drawing Designation	E1 E2 E3
Dimensions (in Inches)
Above Up to 0 0.06 0.06 0.10 0.10 0.16 0.16 0.25 0.25 0.39 0.39 0.63 0.63 0.98 0.98 1.57 1.57 2.48 2.48 3.94	+0.006 +0.010 +0.015 0.008 0.014 0.020 0.010 0.016 0.027 0.014 0.020 0.031 0.016 0.027 0.039 0.020 0.031 0.051 0.027 0.039 0.063 0.031 0.051 0.079 0.039 0.063 0.098 0.051 0.079 0.126

Table 16. Cut Length tolerance for unspliced extrusion

RMA Class	1 - HighPrecision 2 - Precision 3 - Commercial
Drawing Designation.	L1 L2 L3
Length (in Millimeters)
Above Up to 0 40 40 63 63 100 100 160 160 250 250 400 400 630 630 1000 1000 1600 1600 2500 2500 4000 4000	+0.7 +0.04 +1.6 0.08 1.3 2.0 1.0 1.6 2.5 1.3 2.0 3.2 1.6 2.5 4.0 2.0 3.2 5.0 2.5 4.0 6.3 3.2 5.0 10.0 4.0 6.3 12.5 5.0 10.0 16.0 6.3 12.5 20.0 0.16% 0.32% 0.50%
Length (in Inches)
Above Up to 0 1.6 1.6 2.5 2.5 4.0 4.0 6.3 6.3 10.0 10.0 16.0 16.0 25.0 25.0 40.0 40.0 63.0 63.0 100.0 100.0 160.0 160.0	+0.03 +0.04 +0.06 0.03 0.05 0.08 0.04 0.06 0.10 0.05 0.08 0.13 0.06 0.10 0.16 0.8 0.13 0.20 0.10 0.16 0.25 0.13 0.20 0.40 0.16 0.25 0.50 0.20 0.40 0.63 0.25 0.50 0.80 0.16% 0.32% 0.50%

Table 18. Spliced Length Tolerances

RMA Class	1 - High Precision 2 - Precision 3 - Commercial
Drawing Designation	S1 S2 S3
Millimeters
Above Up to 0 250 250 400 400 630 1000 1600 1600 2500 2500 over	+302 +3.2 +7.1 4.0 7.1 8.0 5.0 8.0 9.0 6.3 9.0 10.0 8.0 10.0 11.2 10.0 11.2 12.3 012.5 12.5 16.0
Inches
Above Up to 0 10 10 16 16 25 25 40 40 63 63 100 100 over	+.13 +.25 +.28 .16 .28 .32 .20 .32 .36 .25 .36 .40 .32 .40 .45 .40 .45 .50 .50 .50 .53

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 0 4 4 6.3 6.3 10 10 16 16 25 25 40 40 63 63 100 100 160 160	+0.20 +0.20 +0.35 0.20 0.25 0.40 0.25 0.35 0.50 0.35 0.40 0.70 0.40 0.50 0.80 0.50 0.70 1.00 0.70 0.80 1.30 0.80 1.00 1.60 1.00 1.30 2.00 0.6% 0.8% 1.2%
Nominal Dimensions (in Inches)
Above Up to 0 0.16 0.16 0.25 0.25 0.40 0.40 0.63 0.63 1.00 1.00 1.60 1.60 2.50 2.50 4.00 4.00 6.30 6.30	+0.008 +0.08 +0.014 0.008 0.010 0.016 0.010 0.014 0.020 0.014 0.016 0.028 0.016 0.020 0.032 0.020 0.028 0.040 0.028 0.032 0.051 0.032 0.040 0.063 0.040 0.051 0.079 0.6% 0.8% 1.2%