GD&T Symbol Guide
Unequally Disposed Profile
A profile modifier that shifts the profile tolerance zone unequally inside and outside the true profile.
Definition
Unequally disposed profile is used with line or surface profile to place a profile tolerance zone unevenly about the true profile.
The total tolerance still comes first; the value after the U symbol identifies how much lies outside the material.
Application
Use it when function, cleanup stock, coating, or assembly clearance requires more profile tolerance on one side of the nominal surface.
Castings and coated parts often benefit because excess material may be acceptable on one side but not the other.
Profile Zone Offset Toward One Side
The value after the unequally disposed symbol tells how much of the total profile tolerance lies outside the material.
3D Tolerance Zone
A profile zone where the total tolerance is distributed unequally about the true profile.
Inspection Method
Build the profile zone with the specified unequal distribution, then compare measured points to the shifted boundaries.
A CMM or scan workflow should use the drawing's material-side direction to avoid reversing the offset.
Worked Check: Casting Stock
A surface has profile 0.60 U 0.50, meaning 0.50 mm is outside material and 0.10 mm is inside.
Outside
0.50 mm
Most of the tolerance allows cleanup stock.
Inside
0.60 - 0.50 = 0.10 mm
Only a small inward deviation is permitted.
Compare
Use shifted band
Measured points must stay inside this unequal profile zone.
The callout favors extra outside material while tightly limiting inward deviation.
Comparison Table
| Profile Zone | Distribution | Best Use |
|---|---|---|
| Equal bilateral | Centered | Balanced variation |
| Unequal | Offset | Stock or fit bias |
| Unilateral | All one side | One-sided functional limit |
Notes
If the outside value equals the total tolerance, the zone is unilateral outside the material.
If the outside value is zero, the zone is unilateral inside the material.