Profile of Surface - U in Front of the Tolerance 2

[dingy2]

I just ran across a profile of a surface that had the following tolerance inside the feature control frame:

0.0025|U0.0025

Since this is not outlined in ASME Y14.5M-94, it must be covered with the ISO. Could someone please explain its meaning?

Thanks

Dave D.

http://www.qmsi.ca

 

[powerhound]

Here ya go Dave...

http://www.tec-ease.com/tips/october-05.htm

Powerhound, GDTP T-0419
Production Manager
Inventor 2009
Mastercam X3
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[PaulJackson]

The (U) symbol is introduced in Y14.41-2003 DIGITAL PRODUCT DEFINITION DATA PRACTICES and it has been adopted in the Y14.5M-2008. The number preceeding the (U) symbol is the total profile tolerance and the number following the (U) symbol is the amount of tolerance allocated on the plus material side.

0.0025|(U) 0.0025 means all unilateral + from basic

0.0025|(U) 0 means all unilateral - from basic

0.0025|(U) 0.001 means 0.001 unilateral + from basic and 0.0015 - from basic. "unequal bilateral"

A tolerance without a (U) designation is equal bilateral.

This symbology was adopted so that unequal bilateral and unilateral tolerance allocations do not need to be seperately detailed on the specification.

Paul

 

[powerhound]

So in your case it would mean that the total tolerance zone is .0025 and all of it is unilaterally disposed outward of the true profile. This is in Y14.5M-2008 as well as Y14.41-2003.

Powerhound, GDTP T-0419
Production Manager
Inventor 2009
Mastercam X3
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[dingy2]

Thanks guys.

I just received the ASME Y14.5-2009 online on Friday and haven't been through the changes yet.

Dave D.

http://www.qmsi.ca