Runout or Total Runout? 1

[jag321]

Hi
Please see the attached drawing its a valve bonnet bore

Why cant we use total run out on both the ends or circular runout on both sides....

UV packing comes on the Left side and stem will be passing through the bore

there are two cases the stem may slide up and down or it may rotate please help me with this

the standard followed is ISO....

 

[Belanger]

Why cant we use total run out on both the ends or circular runout on both sides....

You can use total runout on both ends, or circular runout on both sides. So I'm not sure what your question is.

(Also, it's interesting that you mention ISO, yet the numbers seem to be inches.)

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

 

[jag321]

Why wont they make a difference could you please explain...in some cases it is circular one side and total one side...

 

[Belanger]

Circular runout checks the "wobble" effect of a rotating diameter, but it checks individual circular elements (or rings). Each ring could be a slightly different size yet still have perfect runout.

Total runout checks the "wobble" effect of one complete tracing of the entire cylinder, meaning that the indicator travels longitudinally as the thing rotates (think of a spiral).

An easy way to say it: Circular runout is two-dimensional and total runout is three-dimensional. If something passes total runout, it will automatically pass circular runout of the same tolerance.

Now, I don't know why this print uses the different symbols at each end. It depends mainly upon the function of the part. Also, the ease of inspection may play a role in choosing the symbols (particularly in this case because the datum is a combined axis through both ends of the part, which can be tricky).

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

 

[3DDave]

The end with total runout seems to be the one that receives a pressed-in bushing, which means that the cylindricity and the location of the surface are both important.

The end with the runout symbol interfaces with a short press fit (if that) of a bushing and packing. I see that the shorter section doesn't even list a diameter tolerance, indicating that the size and location are unimportant.

Given that one surface is not very long compared to the other, it's not clear why the compound reference is used. I would have given the long surface a position tolerance to the mating flange and a cylindricity control for the press fit and then a total runout tolerance for the other bushing and packing, or just a positional tolerance as runout by itself is a poor overall form control.

Beyond that I'm confused because the section image of the valve is very little like the section of the drawing.

 

[jag321]

Belanger thanks for your insights....interms of inspection time will total runout be higher than circular?

 

[Belanger]

Not necessarily more time, but total runout is a tighter tolerance -- so more likelihood to fail a part.

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

 

[jag321]

The left side dimension accomodates UV packing seal i think it should be total runout(tighter tolerance) whereas the right one not even gets in touch with stem so it could be cirular runout...im i thinking it correct....?