Runout Tolerance Applied on an Assembly 1

[greenimi]

Why runout is used in this figure? (instead of profile)

What would be the difference between using profile (maybe even with dynamic profile modifier) instead of currently shown total runout?
Are there any mathematical difference between shown total runout and profile (again with dynamic profile maybe) ?

 

[Burunduk]

greenimi,
I think that theoretically total runout could be used to control either the major diameter, the minor diameter, and even the pitch diameter of a thread, but not the entire helical surface as a whole feature. The total runout tolerance zone is really only well defined for nominally cylindrical features (or flat ones perpendicular to an axis). Circulat runout can only work for features with circular cross-sections (or flat circular elements), and threads are not round in cross-sections.

Interrupted features such as gears can indeed be controlled by circular or total runout, but that is because you ignore the interruptions and consider only the portions that form a round feature. Threads are not interrupted but the major/minor/pitch diameter could be treated as a cylinder in isolation from the rest of the surface, but only for total runout and not circular runout.

 

[greenimi]

I think applying total runout to the pitch diameter (probably theoretically possible) will create even a more gap between theory and reality.
I know, by default, the position for example will apply to the pitch diameter, but applying runout to the pitch diameter it is, in my opinion, another order of magnitude.

 

[mfgenggear]

on a gear it can be tolerance per AGMA or ISO.
total composite error and tooth to tooth composite error, as well as pitch diameter runout at the pitch diameter. and it is common. there are several ways to measure pitch diameter runout.

 

[greenimi]

on a gear it can be tolerance per AGMA or ISO.
total composite error and tooth to tooth composite error, as well as pitch diameter runout at the pitch diameter. and it is common. there are several ways to measure pitch diameter runout.

Do you have some examples where the practice you stated above is shown? I am curious how other standards show it.
I am not familiar with AGMA. Could you , please, provide more details?

As far as ISO GPS, I cannot find an example there either. I am looking into 1101:2017, with no success in finding something relevant.

Anyone can help?

 

[mfgenggear]

Green
Yes I will provide reference specs.
I am a retired USA gear engineer

 

[greenimi]

Yes I will provide reference specs.
I am a retired USA gear engineer

Perfect. Thank you. I am willing to learn from different area of expertise.

 

[3DDave]

There are entire volumes from AGMA concerning gears.

https://members.agma.org/ has a list.

Maybe this will help: https://khkgears.net/new/gear_knowledge/abcs_of_gears-b/gear_accuracy.html

 

[greenimi]

There are entire volumes from AGMA concerning gears.

https://members.agma.org/ has a list.

Maybe this will help: https://khkgears.net/new/gear_knowledge/abcs_of_gears-b/gear_accuracy.html

Thank you for the references. Clearly something I can use to improve my own education and expertise.

 

[mfgenggear]

yes there is and it is constantly beening updated. there is AGMA 2000 inspection of gears off the top of my head. AGMA quality class will dictate tolerancing and inspection.
but there is a new spec but I have to look it up . you know OG tend to forget stuff. lol

 

[greenimi]

yes there is and it is constantly beening updated. there is AGMA 2000 inspection of gears off the top of my head. AGMA quality class will dictate tolerancing and inspection.
but there is a new spec but I have to look it up . you know OG tend to forget stuff. lol

Yes, I agree. But at least I am aware of other standards that use runout error on the pitch diameter, even maybe their definition of the runout is not strictly in alignment with the Y14.5 definition (per 2009 or even per 2018)

"Runout error is measured by indicating the position of a pin or ball inserted in each tooth space around the gear and taking the largest difference. The values of runout include eccentricity."

 

[mfgenggear]

Green
The methods used to inspect gears and depending on the type of gear.
#1 cnc gear checker
Total index error, tooth to tooh index error
#2 tight mesh with a master gear
Total composite error, tooth to tooth composite error

 

[mfgenggear]

As well as your description using gear wired
One tooth at a time.

 

[mfgenggear]

Per 2018 even is you don't spin the wheel (around the datum axis shown in the FCF) you can call it with runout?
At least, in my original picture 12-16, the wheel/ rotor is not spinned around any of the datums A or B (depicted in the feature control frame), but it is spinned around itself .....more of less like cylindricity.
Can we replace 12-16 with cylindricity (just the top total runout callot/ applied to the cylindrical feature, not the side / face/ planar surface)?
So we have dynamic profile (with customized datum reference frames that have only the rotational degrees of freedom listed) and runout still on the available options, right?

I guess, my point is: you don't NEED a datum axis which is part of the FCF in order to LEGALLY use runout (per 2018), which was not the case per the previous revisions of Y14.5 (1994, 2009), BUt in the same time THEY claim that "The definition of runout tolerances was not changed"......

Am I missing something here?

the constraints are the two bearings holding the wheel spindle. but the verification is only as good as the rim. and the rim placement on the axel. on a lathe or ID grinder. one would true up the chuck to the lathe or ID chuck spindle. one would place the part in the chuck. check rough runout of the part.
then proceed to machine an attribute.
then the required runout with an indicator
would be verified

 

[Burunduk]

I believe the following specification could have communicated correctly what probably is the intent. This control could have been achieved without noticing under the now superseded dial indicator based definition, even without datum C or the customization - as done in the original figure. The original fails to work as intended under the tolerance zone based definition of runout.



The inspection fixture would include simulators for datums A and B. Datum feature simulator C is integral within the assembly.

 

[greenimi]

Burunduk,
In your last reply/ picture posted, do you think if B and C are switched in the DRF, would still be a valid callout? I mean datum feature precedence order will be in "more" alignment with the overall Y14.5 theory, would't it?
Just asking ...

 

[Burunduk]

greenimi,
Could be. Because C constrains more degrees of freedom. In fact, that's how they do it in Figure 7-57 Customized Datum Reference Frame - the tertiary locks the third rotation. Good point.

 

[Burunduk]

Come to think of it, it would probably make more sense to show the coordinate system on datum C too. Because that's where the Y and Z translations are constrained.