Dimensional Tolerances for Aluminum Extrusions

Aavid Thermalloy’s aluminum extrusions comply with or are better than the standard commercial tolerances established by the Aluminum Association, Inc. The tolerance for an extrusion dimension is a function of the size of the particular dimension and the diameter of the extrusion die as shown in Table A. The illustration shown is a typical flatback extrusion. Tolerances for extreme ratios and some large extrusions tend to exceed the tolerances listed on this table and, conversely, some of the smaller (less than 7 inch diagonal) extrusions can be supplied with half of the commercial tolerances.
Dimensional Tolerance for Aluminum Extrusions When defining machined flatness, use the statement of 0.001"/in. to preclude steps allowable with other methods of defining flatness. See Table B.

Aavid Thermalloy's standard machining tolerances are +/- 0.010 in. for lead-in dimensions from edge/datum line, and +/- 0.005 in. thereafter from feature to feature. Due to the nature of extruded aluminum, this may not coincide exactly with the generic tolerances listed on most drawing title blocks. In the majority of cases, however, it is sufficient. If you require tighter tolerance, we can accommodate this need with additional machining. Please contact our Applications Engineering Department with any questions or concerns regarding these tolerances.

Table C lists the typical properties of 6063-T5 Aluminum extrusion alloy.

Table A: Typical Tolerances for
Aluminum Extrusions
Dimension A +/- Tolerance on "A"
Diameter of Extrusion Die
inches [mm] Up to 10 in [254 mm]
inches [mm]
> 10 in [254 mm]
inches [mm]
<.125 [3.0] 0.006 [0.15] 0.014 [0.36]
0.125 - .249 [3.0 - 6.3] 0.007 [0.18] 0.015 [0.38]
0.250 - .499 [6.4 - 12.6] 0.008 [0.21] 0.016 [0.41]
0.500 - .749 [12.7 - 19.0] 0.009 [0.23] 0.017 [0.43]
0.750 - .999 [19.1 - 25.3] 0.01 [0.25] 0.018 [0.46]
1.000 - 1.499 [25.4 - 38.1] 0.012 [0.30] 0.019 [0.48]
1.500 - 1.999 [38.2 - 50.7] 0.014 [0.35] 0.024 [0.61]
2.000 - 3.999 [50.8 - 101.6] 0.024 [0.61] 0.034 [0.86]
4.000 - 5.999 [101.7 - 152.4] 0.034 [0.86] 0.044 [1.12]
6.000 - 7.999 [152.5 - 203.2] 0.044 [1.12] 0.054 [1.37]
8.000 - 9.999 [203.3 - 254] 0.054 [1.37] 0.064 [1.63]
10.000 - 11.999 [254.1 - 304.7]   0.074 [1.88]
12.000 - 13.999 [304.8 - 355.5]   0.084 [2.13]
14.000 - 15.999 [355.6 - 406.3]   0.094 [2.39]
16.000 - 17.999 [406.4 - 457.1]   0.104 [2.64]
18.000 - 19.999 [457.2 - 508]   0.114 [2.90]
Flatness and surface roughness tolerances of extruded surfaces
are also useful for heat sink applications.
The following table lists typical ranges:
Table B:
Flatness and Surface Roughness Table
Aluminum
Surface
Flatness
(in/in)
Surface
Roughness (RMS)
As Extruded .004 (up to .006) 125 - 64
Sanding
(except for edge rounding)
.002/.003 64 - 32
Machined .001 64 or better
Table C:
Typical Properties of 6063-T5 Aluminum Extrusion Alloy*
Physical Property Value
Average Coefficient of Thermal Expansion 13.0 µin/°F (68° - 212 °F)
Approximate Melting Range 1140°F - 1210°F
Thermal Conductivity 1450 BTU - in/ft² hr °F (@ 77°F)
Electrical Resistivity 2.8 µOhm-cm (@ 68°F)
Ultimate Strength 27,000 PSI
Yield Strength 21,000 PSI
Elongation 12%
(% in 2 in, 1/16" thick specimen)
Hardness Rockwell H 60
(60 kg load, 1/8" ball)
Ultimate Sheer Strength 17,000 PSI
Fatigue Endurance Limit 10,000 PSI
(500 x 106 cycles Moore Mach.)
Modulus of Elasticity 10 (106 PSI)
* Source: Aluminum Standards and Data, 1988 Aluminum Association Inc.