huangyhg

using profile to position a feature?
very simple part. a rectangular hole in a rectangular block. rectangular hole size is dimensioned with basic dim's and has a profile callout pointing to it. three datums called out - bottom (a) of block and two edges (b & c). profile is called out to all three datums. there are also basic dim's locating the rectangular hole from the edges (datums b & c).
local "expert" says this is okay, that we can use profile to locate the rectangular hole. i disagree, argueing that profile is a tolerance of a feature size, not a tolerance of location. therefore, dim's that locate rectangular hole should become unbasic, or just toleranced dim's - or - add positional tolerance callout to rectangular hole and keep dim's basic.
who's right?
thanks
profile can be used to control size, form, orientation, and location (per y14.5-1944, para 6.5.1). your expert is right. figure 6-19 in same spec is probably close to what you're describing.

looks like the profile in this case was used correctly. profiles do not reflect features of size but surfaces and it looks like the surfaces are reflected from datum b & c and, probably, perpendicular to datum a.
one could also have used a positional tolerance if the hole was shown as a feature of size with tolerances with basic dimensions to its centre.
dave d.
stevemartin, i see in 6.5.1 it says "location", but i've never seen it applied that way.
figure 6-19 was my suggestion on the way it should be done. it shows positional tolerance. as it is, the only control frames on the drawing in question are the profile for the rectangular hole and profile for the outside edges of the rectangular block. they are each held to different tolerances. i just don't see how that can relate to location. if it can relate to location, what is the tolerance of the basic dim's that locate the rectangular hole?
not trying to be contrary, just trying to wrap my head around something that seems illogical to me.
thanks.
randy64,
can the profile tolerance be inspected?
will a part that conforms to the profile tolerance work?
will a part not conforming to the profile tolerance not work?
asme y14.5m is a language, not a procedure. there usually is more than one way to express your requirement, although there are often subtle differences in the resulting geometry. a profile tolerance explicitly shows an mmc, which probably, is what you need. the geometry shown by a positional tolerance and ± tolerances on the slot show something a little more complex.
jhg
drawoh, i'm not sure i see what you're saying has to do with my question. my question concerns how the profile callout can be used to locate the rectangular hole within the rectangular block. since both rectangular shapes have a profile tolerance that means their edges must fall within their respective tolerance "bands" or "zones." what i don't see is how those profile callouts can have anything to do with actually locating one feature (or their tolerance "bands") to another.
???????
sounds like your expert is correct, and that it's a permissable way of handling this.
in fig 6-19 the positional tolerance is effectively a refinement.
it will come down to function if the extra control is needed.
your idea of combining basic & +- dimensions in your op sounds incorrect.
kenat,
i agree as well, the situation you have described is valid and legal. as dave said, profile is not applied to features of size but rather the profile of the feature.
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okay. i guess i'm not being clear. if you look at fig 6-19, that is pretty much my situation, with the following three important differences: (1) there is no positional tolerance, (2) there is a profile callout to the outline of the block and (3) the profile callout to the interior feature (in my case a rectangular hole) is called out to 3 datums, a, b & c.
given that, my question is: what is the tolerance (or more specifically, where would i find the tolerance) on the basic dimensions that locate the interior feature (in fig 6-19 it's the 25 dimension)?
so far a couple of you have said "the expert is correct", but haven't answered my specific questions. i guess i can accept that i'm wrong if someone would explain to me how you can use profile to locate features. no one has done that yet.
again, not trying to be nasty, but i need and want to know this stuff so i can be able to defend/explain it to my customer and my detailers.
thanks.
the combined basic dimensions (& geometry) define the theoretically perfect form/location/orientation etc. of the surfaces.
the profile tolerance then defines how much the actual surfaces are permited to vary from that.
the point is the surface profile tolerance controls location as well as the other things. the location tolerance is part of the surface profile tolerance.
kenat,
"the location tolerance is part of the surface profile tolerance."
this doesn't answer my question. specifically, how is the location tolerance discerned from the profile tolerance? is there a formula to do this? is a percentage of the profile tolerance used to determine the location?
here's the way i see it: if you have two features that have profile tolerances called out to them, they are independent of each other. profile only controls the form of each feature independently. putting a basic dimension between the two features does not control location via the profile. i think you need another control, like positional tolerance, as shown in fig 6-19.
i am trying to be open minded on this, but so far nobody has taken the time to fully explain how this would work using only profile tolerancing.
thanks.

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