Runout on a flat surface in a stack

[bspriggs]

We have many instances where runout was used on a flat surface. The basic premise is the engineer at the time was attempting to control the "wobble" on that surface (basically perpendicularity)and back in the day TIR was the goto for prints. If given the choice I would write a request to change all of these and replace with either perpendicularity or profile (but alas...). My question is, when performing a stack-up on a part where the end face has surface runout applied what effect does it have? Should it be added as a ± in the calculations or does Rule #1 come into play and the runout only refines the zone?

 

[greenimi]

Print, print, print,

I think can be eitherway.
What has been concluded in this thread:

http://www.eng-tips.com/viewthread.cfm?qid=430633

is that the runout is not controlling the surface location!

 

[CheckerHater]

Total runout in axial direction is no different from perpendicularity.
So, no size control, more of a refinement.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[bspriggs]

Thanks for the reply. That was how I understand it as well (treat it just like perpendicularity). Every now and again you look at something an say....hmmm that just does look right....

Thanks for the input!

 

[Belanger]

A quick side note -- in your OP you simply mentioned "runout." But there is no runout symbol. It would be either "circular runout" or "total runout."
I mention this because if you're thinking of circular runout, then it's not the same as perpendicularity. Only if the print uses the total runout symbol can we say that it's equivalent to perpendicularity.

 

[bspriggs]

True you are correct. I guess I am looking for both circular and total. We have instances where we see both in our drawings. Circular I believe is more widely used though. So we established total runout acts as a perpendicularity in stacks, what about circular?

 

[Belanger]

It depends on what the stack is solving for. I don't deal with many stacks that involve runout on an end face, simply because the parts I'm thinking of would already have an overall length within which the runout tolerances would operate.

But if you're looking at a stack for clearance near that end face (so it doesn't rub against another piece), then total runout (perpendicularity) would be a factor. Circular runout wouldn't -- it would allow for a pointed/crowned face, so I think you'd have to look for another tolerance that controls the orientation and form of that face.