Spherical Tolerance Zone

[CheckerHater]

I recently run into question that I thought could be interesting for the rest of this forum: what spherical tolerance zone is good for?

ASME Y14.5-2009 Fig. 7-35 shows obvious application for locating spherical feature of size.

Now, if I want to locate point in space, there is nothing wrong about that point being contained within spherical tolerance zone.
One possible use is shown on the enclosed picture; all opinions are welcome.

 

[axym]

CH,

Yes, we should be able to derive the virtual sharp of a cone. We just need to explicitly specify the method used for the derivation. For a sphere, the maximum inscribed/circumscribed inverse sphere works well but for a cone there is no obvious equivalent. The main question relates to the included angle of the inverse feature - is this angle held constant, or is some sort of fitting algorithm used? In your drawing, the diameter of the cone is dimensioned with a plus/minus tolerance and there is no basic angle.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[MechNorth]

I support Evan on this one. I have no problem with the concept of tolerancing a point, but the simulation (AME) is a challenge. Is the AME the cone, or the point? Picture a cone whose apex is for some reason truncated slightly, but still forms a "point"; is that non-apex the point in question, or is it the apex of the conical taper? That, to me, would have to be defined on the drawing.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[CheckerHater]

So, in order for “extension of principle” to work we have to accompany our tolerancing scheme with some sort of a note.
Something like “DERIVED VIRTUAL SHARP”?

 

[MechNorth]

CH, at the moment there's nothing that I know of that defines a "point", so something has to explain it.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com