yang686526

profile on coplanar surfaces
would it be acceptable to use profile on coplanar surfaces with respect to a datum surface that is perpendicular? basically treating that profile tolerance like perpendicularity to those surfaces. i've seen it done with basic profile but wasn't sure about it when applied to coplanar surfaces. thanks in advance.
eng-tips forums is member supported.
if i understand you correctly section 6.5.6 of asme y14.5m-1994 may be of use as it talks about using surface profile for coplanarity control. it mentions that no datum reference is stated as in flatness.
i'm wondering if this would be a case where you have 2 controls. surface profile for the coplanarity and then a separate perpendicularity. unless of course the value on both is the same, in which case it seems logical to reference the datum but i'm not sure the standard explicitly covers this case.
good question.
kenat,
yes, you are understanding correctly. you pretty much hit the nail on the head. exactly like the example you presented. seems logical but i am not sure. if you can call out one less control all the better because you know that cash register is ringing everytime we do something like this (i think they count up all symbols & multiply a cost) - of course in the end we want it to be understood too.
unless one of the better educated/more experienced posters can give a more definitive answer then i'd say yes you can reference it.
you are using it like normal surface profile and get the coplanarity out from the control of surface profile over location & orientation.
kenat,
yes, it would be acceptable to use surface profile on coplanar surfaces with respect to a datum surface that is perpendicular. this can be thought of as one continuous tolerance zone that both surfaces must lie within, or two separate zones that are exactly coplanar to each other. the zone (or zones) are exactly perpendicular to the datum. this would control each surfaces's perpendicularity to the datum as well as their coplanarity to each other.
the combination of 2 controls that kenat mentioned would give a similar overall result, but not exactly the same. applying a perpendicularity tolerance to the 2 surfaces would control them individually - there would be 2 zones that are both exactly perpendicular to the datum but not coplanar to each other. the surface profile tolerance would control the coplanarity. again, this combination is not exactly the same as the surface profile with the datum reference.
it sounds like the control that you want is the equivalent of "regular" perpendicularity, except applied to a pair of 2 surfaces that act as one interrupted surface. i would go with the surface profile with the datum reference.
evan janeshewski
axymetrix quality engineering inc.
i want to treat the surfaces as one and that was a great explanation.