U in the FCF

[Sekhar]

Could some one explain, the meaning of" U" in the FCF -Image attached

[Darrollh]

Unequal profile

[sealevel]

NB: .006 is the total tolerance.
So for an FCF with an Unequally disposed profile:
The .002 after the 'U' allows the feature .002 ADDITIONAL material. And then you subtract of .006 - .002, .which gives you 004 --- the allowed amount of material REMOVED from feature .

[JEFMAN]

What sealevel said !
U in ASME is UZ in ISO.
Unilateral and Unequally Disposed Profile Tolerance [ASME Y14.5-2009 Section 8.3.1.2] - To indicate that a profile of a surface tolerance is not symmetrical about the true profile, this symbol is used. The first value in the feature control frame is the total width of the profile tolerance. The value following the symbol is the amount of the tolerance that is in the direction that would allow additional material to be added to the true profile.


Some more GD&T info here :
https://www.tec-ease.com/gdt-terms.php
https://gdtseminars.com/wp-content/u...Chart_2013.pdf
http://www.g-wlearning.com/cad/97816...r/pdf/appg.pdf

Without forgettng the excellent presentation of Rob Jensen :
https://www.gagesite.com/documents/E...0Standards.pdf

[vpt.se]

+0.002/-0.004 from nominal, I believe

[AndersI]

At the moment, PC-DMIS only allows the ASME notation. Watch out for the difference between ASME and ISO - in ASME you tell what the Upper tolerance is (U) 0.002, in ISO you tell how the tolerance zone has been moved from the symmetrical case (UZ -0.002).

Also note that PC-DMIS FCF will not let you (U) more than the tolerance width, if your tolerance is +/+ or -/- you can only do it with a Legacy dimension.

[Rich P]

(U) in FCF signifies material "on" allowance in an unequal distributed tolerance zone
.002 is Material "on" Max from nominal .004 material "off" from nominal
Profile Surface or Line .006 (U).006 -A- is +.006-.000 from nominal-material must be at or plus to nominal
Profile Surface or Line .006 (U).000 -A- is +.000-.006 from nominal-material must be at or less material than nominal
Be aware of difference for a material "on" and Material "off" if they are an ID or Outer surface.

[Matthew D. Hoedeman]

(U) in FCF signifies material "on" allowance in an unequal distributed tolerance zone
.002 is Material "on" Max from nominal .004 material "off" from nominal
Profile Surface or Line .006 (U).006 -A- is +.006-.000 from nominal-material must be at or plus to nominal
Profile Surface or Line .006 (U).000 -A- is +.000-.006 from nominal-material must be at or less material than nominal
Be aware of difference for a material "on" and Material "off" if they are an ID or Outer surface.

IN THEORY, the arrow (leader) of the FCF should be pointing TO the side of stock that the U applies to. Also, IN THEORY, the arrow (leader) is NOT TO be passing through the part to point to the side of stock the U applies to.

U-FCF.jpg

[sealevel]

A simpleton like myself needs pictures to lÔÔk at in the ASME standard....wording alone is just sooooo dry.


profile.PNG

and personally? I don't care much for the 'Alternate Practice' with that dash line clutter

[SingularitY]

Can't dispute the standard.

[Sekhar]

Thanks for all great explanations. I am not very familiar with profile FCF tolerance. Now understand clearly going to apply once reach the office tomorrow.