【转帖】profile of surface - u in front of the tolerance
 

profile of surface - u in front of the tolerance
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.
here ya go dave...
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
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.
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thanks guys.
i just received the asme y14.5-2009 online on friday and haven't been through the changes yet.
dave d.