Profile to Surface Modifier Question

[huntengine]

I have an issue trying to figure out how to correctly display the profile to surface callout on my component print. The component mates to another component in the assembly and there is no gap between the two in CAD (I don't have the option to modify the CAD). The two are welded together to make the assembly and I want a gap between the two for the welding process. I want all of the gap tolerance to be applied to the component I'm making this print for and I want between a .5mm and 1.0mm gap. So with the CAD showing no gap I'm not sure if the Unilateral modifier is the correct modifier to use since I'm looking at -0.5 to -1.0 tolerance on this surface.

 

[JNieman]

If you apply a unilateral tolerance modifier that puts the tolerance zone completely on the LMC/LMB side, then you will be incredibly unlikely to ever see a mating situation where there is no gap. It would require the mating part to be completely flat, and your part to be completely flat exactly at MMC/MMB. There will be /some/ gap, but obviously it will still be allowed to be miniscule, so I guess, you'd first have to be very sure that 0.5 is your absolutely minimum required gap.

Otherwise, no, you cannot use a modifire to a PoS control that gives you what you're asking. This very thing was recently discussed here, as chance would have it:

http://www.eng-tips.com/viewthread.cfm?qid=401396

which seems to conclude that -as far as the ASME standard is concerned- the true profile has to be included in the tolerance zone to make sense.

 

[huntengine]

Thanks for the link. I think I'll be using a general note on this one instead of the feature control frame.

 

[wearules]