Question 1

What is EN 755-9?

Accepted Answer

EN 755-9 specifies tolerances on dimensions and form for aluminium and aluminium alloy extruded profiles for general engineering applications, with a cross section contained within a circumscribing circle of up to 800 mm.

Question 2

What is the circumscribing circle (CD)?

Accepted Answer

CD is the diameter of the smallest circle that contains the whole cross section of the profile. Tolerances on H, wall thickness and length depend on it.

Question 3

How do I know if my alloy is Group I or Group II?

Accepted Answer

EN 755-9 Table 1 divides alloys into two groups. Group I includes common extrusion alloys such as 6060, 6063 and 6005A. Group II includes alloys such as 6061, 6082, 7075 and 2014, and generally has larger tolerances. Type your alloy in the calculator and the group is detected automatically.

Question 4

How is the tolerance on H calculated across an open end?

Accepted Answer

For H measured across an open end, the tolerance from the standard H table is increased by an addition that depends on the open end dimension E. For example, with H 40 mm, E 50 mm, CD 100 to 200 mm and Group II, the tolerance is plus or minus 0.90 mm plus 0.40 mm, a total of plus or minus 1.30 mm.

Question 5

What is EN 12020-2 and when does it apply?

Accepted Answer

EN 12020-2 specifies tolerances on dimensions and form for extruded precision profiles in alloys EN AW-6060 and EN AW-6063, mainly for architectural applications, with a circumscribing circle of up to 350 mm. It has closer tolerances than EN 755-9. For other alloys or larger profiles use EN 755-9.

Question 6

Does the calculator include Indian Standard tolerances?

Accepted Answer

Yes. Choose IS 3965 for solid aluminium profiles or IS 6477 for hollow profiles. Each gives the tolerance on width and on thickness, where thickness tolerance depends on both thickness and width.

Question 7

What does EN 755-8 cover?

Accepted Answer

EN 755-8 gives tolerances on dimensions and form for extruded porthole tubes: round tubes from 8 to 450 mm outside diameter, and square, rectangular, hexagonal and octagonal tubes with a circumscribing circle of 10 to 350 mm. It does not apply to seamless (die/mandrel) tubes, which are covered by EN 755-7.

Aluminium Extrusion Tolerance Calculator

Select standard

Find Aluminium Suppliers

Weight Calculator

Sheet & Circle Calculator

Weight Formula Guide