Perpendicularity

[ccarpent]

This may sound very basic, but I need to be sure and I can not find an example in the spec. (ASME Y14.5M 1994). When a plane surface is toleranced perpendicular to a datum that is a cylindrical feature, must it be perpendicular all around or just in the view shown? I believe all around.
Thanks
Chuck

 

[powerhound]

There are good points made regarding this topic but I'm still having trouble reconciling just outright ignoring Fig. 6-37 in the 94 standard. It has been pointed out several times in this thread that the features shown in 6-37 are cylindrical, as opposed to one planar feature as stated in the OP. My argument is that the tolerance zones for both of the scenarios are identical and thus the principle invoked by Fig. 6-37 should apply, by extension of principle at the very least; however, I think there is a strong enough argument made just on the merits of the figure alone. Now, whether or not the figure itself makes sense, or is even helpful, is another story.



Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[axym]

J-P,

Yes, there is still some view dependence with Straightness tolerances. It would be nice if they got rid of this as well, and oriented the zones with a more rigorous datum-based method.

I hadn't noticed the break line in the Position FCF in Fig. 6-6, thanks for pointing that out. It probably would have been more clear if they had just included datum feature B as in Fig. 6-8.

powerhound,

I agree with you that the tolerance zones are identical - both are two parallel planes that are perpendicular to a datum axis. But I guess I'm not sure exactly what the note in 6-37 is intended to mean - "This applies only to the view on which it is specified". Would anything be different if that note were not there? I'm not sure what (if any) principle is being invoked here. It's true that the only direction of rotational control is shown in the side view, but there's nothing that is being "applied" only in the side view and not applied in the others. The fact that there is only one direction of rotational control is a consequence of the combination of considered feature geometry and datum feature geometry, not a consequence of applying any special constraints on the tolerance zone.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[powerhound]

I don't know what the note means either but I am assuming someone out there does. It's a pretty weird way to call out hole orientation and I would probably never try to control perp of a hole to an axis like that.

Thanks for the help.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II