Position Tolerance of a square feature on a disk

[jdmmech]

I have a disk that is inserted in a cylinder. A square sleeve will be inserted and welded to the square bore of the disk and I am trying to center the hole on the disk. Is a position tolerance the best way to do this? I have read that you can use position with any feature, not just a circle. Even though it is a square, the diameter callout still seems correct to me as the tolerance zone.

Otherwise, setting an X-Y tolerance on the distance to the centerline would give a similar result. I guess the only difference there is the square vs circular tolerance zone.

Is this correct? Thank you.

http://files.engineering.com/getfil...1751-40fe-afeb-6e22ec423686&file=Picture1.png

http://files.engineering.com/getfil...1e25-4cbc-b38a-510c8e3ce8bb&file=Picture2.png

 

[Belanger]

I was kinda sure that an "all-around" profile would need basic dims. That's why I started the other thread. But you and others made the case that the standard doesn't really require that, so I backed down.

With that in mind, this example of the square slot with all-around profile and non-basic dims seems to be legal per Y14.5. But I still don't have to like it

As for your question, yes it does seem to be the only way to control form/orientation but not size for an unusual shape.


John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[3DDave]

I don't see the jump to applying profile to this case. The control is for deviation from a true profile and this hasn't got one, though I see the confusion where there is a reference to refining features controlled by size dimensions. However, the example I see in the standard is for a truncated cone, which hasn't got a size dimension. Instead it is a compound of a location dimension and a local size dimension. Since the two are interdependent it isn't -a- size dimension. It's more like the two dimensions that can be used for a chamfer. Delete either one and the notion of size goes away.

 

[Belanger]

Dave, Fig. 8-18 in the standard does indeed have a size location. This is because the local size you speak of is anchored to datum B (whereas in Fig. 8-17 it floats since there are no datum references, so I might agree with you there). So if we say that profile can be used in Fig. 8-18 with a non-basic dim defining the true profile, then there is nothing in Y14.5 to say that this example of the square slot is incorrect.

Also, feel free to weigh in on the other thread ("must profile be applied to a basic profile?").

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[3DDave]

The reason I say it is compound is that the cone is guaranteed to have a given size at some axial location, and it will have some size at a given location at an arbitrary distance along the axis. As such neither dimension is stand-alone and is a compound dimension that is neither size nor location.

Without datum B the form and radial location tolerance of the cone is still defined; what the diameter tolerance changes is the axial location of the flat relative to the cone apex. As such, the profile tolerance does not refine the diameter control at that location.

 

[pylfrm]

I'm with 3DDave here. I don't think the secondary datum reference of the profile tolerance has any effect at all in Fig. 8-18. Without a complete basic relationship to datum B, the profile tolerance zone can float axially (as in Fig. 8-27). Without a fixed axial reference, size has no meaning for the cone.

- pylfrm