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Tolerances in Aluminum Extrusion

Aluminum extrusion tolerances are applied to the physical dimensions of a part, critical to that part's success. Some dimensions to which tolerances are applied in aluminum extrusions include:

  • Flatness
  • Straightness
  • Twist
  • Diameter
  • Cross Sections
  • Length
  • Surface Roughness
  • Wall Thickness
  • Curved Surfaces

 

Typical Aluminum Extrusion Tolerances

The tolerance for an extrusion dimension is:

  • The diameter of the extrusion die, and
  • The function of the size of that particular dimension

 

Note: You can click on the table to view a larger image.

Typical Aluminum Extrusion Tolerances

Note: Numbers rounded off to nearest decimal.

Standard Aluminum Extrusion Tolerances

Noted here are:

  1. Flatness
  2. Squareness
  3. Straightness Along the Length of the Extrusion
  4. Twists Along the Length of the Extrusion
  5. Flatness and Surface Roughness

 

Flatness

This tolerance applies to any one inch along the surface of the profile or tolerance, multiplied by the extrusions width along the gradual deviation from 'flat'. Note that flatness is checked by using a feeler gauges and a straight edge.

For Hollow Profiles:

Note: You can click on the table to view a larger image.

Flatness Tolerance for Hollow Parts

Note: Numbers rounded off to nearest decimal.

For Solid, Bars and Semi-Hollow Profiles:

Note: You can click on the table to view a larger image.

For Solid Bars and Semi Hollow Profiles

Note: Numbers rounded off to nearest decimal.

Squareness

Squareness is checked by making use of a protractor, or a feeler or square gauge. The standard allowable when it comes to squareness is +/- 1° from the specified angle of the profile.

For example, if a part is 45°, ChinaSavvy is allowed up to 46° up and a 44° down. Here, 1° equals 0.017" per inch. For example, if a part has a leg with a 4 inch height, ChinaSavvy is allowed a total of 0.068" from the tip of the leg.

Straightness Along the Length of the Extrusion

Straightness is checked by making placing the extruded part on the granite block or any straight edge. The amount of bow is measured using feeler gauges.

The standard allowable tolerance here is 0.012" per foot. For example, when a part is six feet long, a bow of 0.072" over the entire length is allowable.

Twists Along the Length of the Extrusion

Twists are checked by placing the extruded part onto a granite block or a flat surface. One corner is held down and the amount of rise on the opposite, diagonal corner is then measured by making use of a feeler gauge.

Note: You can click on the table to view a larger image.

Twists Along the Length of the Extrusion

Note: Numbers rounded off to nearest decimal.

Some guidelines to apply to the above mentioned tolerances:

Note: You can click on the table to view a larger image.

Some guidelines to apply to the above mentioned tolerances

Note: Numbers rounded off to nearest decimal.

 

Flatness and Surface Roughness

These tolerances become useful in heat sink applications and are typically as follows:

Note: You can click on the table to view a larger image.

Flatness and Surface Roughness

Note: Numbers rounded off to nearest decimal.

Non-Standard Mechanical Aluminum Extrusion Tolerances

Loose and close dimensional tolerances that are relative to the industry's standards can also be specified in cases where it is called for to meet requirements.

For tighter mechanical tolerances, ChinaSavvy is capable of making the needed modifications to the extrusion die. Modifications however will lead to a slower extrusion rate, increased inspections and, in some cases, a higher cost and a higher extrusion rejection rate.

We are also capable of suggesting die design changes, which will help to achieve fit, functional and form requirements set out by our clients.

 

Back To Main Page: Aluminum Extrusions

Further Suggested Reading:

 

Get a quotation about aluminium extrusion here

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