Best fit profile of a surface
Best fit profile of a surface
(OP)
I have a question on the meaning of a profile symbol with no feature control frame, does this mean best fit? The drawing has multiple profile specs on it all with control frames attached, but has one with no control frame just the tolerance and a leader coming out from the bottom of the profile box
calling out this profile as datum -A-
Thanks for the Help
calling out this profile as datum -A-
Thanks for the Help





RE: Best fit profile of a surface
In any case, profile of a surface is a total tolerance meaning all points of the considered feature(s) must fit inside the profile tolerance zone. You might check out the Tip found at: http://www.tec-ease.com/tips/july-98.htm
RE: Best fit profile of a surface
Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development
www.profileservices.ca
RE: Best fit profile of a surface
RE: Best fit profile of a surface
http://www.profileservices.ca/files/tidbits
In this case, without the datum reference, the FCF prescribes a tolerance zone symmetrically offset from the BASIC (ideal or theoretical design) surface, without respect to orientation wrt any datums.
Per ASME Y14.5M-1994, 4.5.10.1 - Mathematically Defined Surface; It is sometimes necessary to identify a compound curve or a contoured surface as a datum feature. Such a feature can be used as a datum feature only when it can be mathematically defined and can be related to a three-plane datum reference frame. In such cases, the theoretically true geometric counterpart of the shape is used to establish the datum.
In the explanation, I've elected to orient datum-A so that datum-B (targets) can be easily established horizontally; it could have been oriented otherwise wrt the inspection table as preferred.
Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development
www.profileservices.ca
RE: Best fit profile of a surface
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Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development
www.profileservices.ca
RE: Best fit profile of a surface