Symbol:  Ⓤ

Definition:

The Unequally Disposed Profile Tolerance Symbol is only ever seen when used in conjunction with the symbols for profile of a surface and profile of a line. The unequally disposed symbol is used to apply unilateral or unequal tolerance zones to a profile of a part.

Above is an example of a how the unequally disposed profile symbol is used in a feature control frame.  

A) Total tolerance of the profile 

B) Unequally disposed profile symbol 

C) Portion of total tolerance that lies outside of the part 

The unequally disposed profile symbol is placed directly after the profile tolerance value. As always, the value after the profile symbol is the TOTAL tolerance applied to the surface. However, when using the unequally disposed symbol, a second value is added after the unequally disposed profile symbol. This value is the amount of the total tolerance that lies outside of the material.

When the unequally disposed profile symbol is used in the feature control frame (FCF) as shown below, the tolerance zone will be unequally disposed about the true profile. See below:

 

 

To further clarify, if this value equals the total profile tolerance, then all of the total profile tolerance is located outside of the material. This is commonly known as a unilateral tolerance zone. See below: 

 

 

Conversely if the value that follows the unequally disposed profile symbol is zero, then all of the total profile tolerance lies inside the material. This is also commonly known as a unilateral tolerance zone.  See below: 

 

Reasons for Use: 

There are many reasons the unequally disposed symbol may be used. Often drawings for castings will utilize this symbol to place all the tolerance onto the outside of the part to ensure the part could be cleaned up during processing. Other industries might utilize the symbol to ensure fit-up during assembly, especially if there is any secondary processing that adds material to the surface like powder coating. 

Additional Resources: 

Symbol Definitions

  • ASME Y-14.5 2018 Section 6.3.22
  • ASME Y-14.5 2009 Section 3.3.22

Profile of a Surface Symbolhttps://www.gdandtbasics.com/profile-of-a-surface 

Profile of a Line Symbolhttps://www.gdandtbasics.com/profile-of-a-line 

Blog Article on Unilateral vs Bilateralhttps://www.gdandtbasics.com/profile-of-a-surface-unilateral-vs-bilateral/

 

 

 


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