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CAN RUNOUT BE USED ON A INTERRUPTED DIAMETER
- Thread starter bxbzq
- Start date
pmarc
Mechanical
- Sep 2, 2008
- 3,248
dgallup,
Your concern is reasonable, however I would say this problem may happen even when actual runout error of simple regular cylinder is inspected. Picture a shaft comprised of two cylinders - one is datum feature, second is toleranced relative to the first with total runout. In most cases there will be a fillet between the two cylinders. So during the inspection there will be also a possibility that dial indicator will go beyond toleranced cylindrical surface, touch the fillet and in consequence the reading will be distorted.
Bxbzq's part does not have to be inspected by continuous rotation 360 degrees around datum axis. This can be done slice after slice. The key thing is just to make sure that the readings are not zeroed between the slices.
Frank,
If the functional requirement on G. Henzold's picture is to keep the shaft parallel to datum plane A, why not to apply parallelism tolerance?
If the functional requirement is to keep the shaft parallel to datum plane A and located from datum plane A, why not to apply position tolerance (with possible refinement of parallelism, if needed)?
Why would somebody want to check circular runout in this case?
Your concern is reasonable, however I would say this problem may happen even when actual runout error of simple regular cylinder is inspected. Picture a shaft comprised of two cylinders - one is datum feature, second is toleranced relative to the first with total runout. In most cases there will be a fillet between the two cylinders. So during the inspection there will be also a possibility that dial indicator will go beyond toleranced cylindrical surface, touch the fillet and in consequence the reading will be distorted.
Bxbzq's part does not have to be inspected by continuous rotation 360 degrees around datum axis. This can be done slice after slice. The key thing is just to make sure that the readings are not zeroed between the slices.
Frank,
If the functional requirement on G. Henzold's picture is to keep the shaft parallel to datum plane A, why not to apply parallelism tolerance?
If the functional requirement is to keep the shaft parallel to datum plane A and located from datum plane A, why not to apply position tolerance (with possible refinement of parallelism, if needed)?
Why would somebody want to check circular runout in this case?
pmarc -- your suggestion of parallelism on that shaft would not be able to detect circularity errors; that's the only hitch that I see.
A runout tolerance on that shaft would control the entire form (cylindricity), as well as orientation (parallelism), and location (although only height location, not coaxial location as intended by runout). No other control can do just those three things (not even profile).
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
A runout tolerance on that shaft would control the entire form (cylindricity), as well as orientation (parallelism), and location (although only height location, not coaxial location as intended by runout). No other control can do just those three things (not even profile).
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
pmarc
Mechanical
- Sep 2, 2008
- 3,248
J-P,
Of course neither location nor parallelism would be able to detect circularity errors. But do you really think that assembly level drawing is the proper place to check circularity error of the shaft? In my opinion this is one of the characteristics, apart from shaft size tolerance, that can be easily provided by engine manufacturer without necessity of simulating working conditions of the engine. Besides, even if there was a need to check the circularity, why not to apply direct circularity callout in addition to position and/or parallelism callouts. Why to make up callouts that are not supported by any standard and actually (in my opinion) does not reflect functional requirements?
Of course neither location nor parallelism would be able to detect circularity errors. But do you really think that assembly level drawing is the proper place to check circularity error of the shaft? In my opinion this is one of the characteristics, apart from shaft size tolerance, that can be easily provided by engine manufacturer without necessity of simulating working conditions of the engine. Besides, even if there was a need to check the circularity, why not to apply direct circularity callout in addition to position and/or parallelism callouts. Why to make up callouts that are not supported by any standard and actually (in my opinion) does not reflect functional requirements?
Sure, an assembly drawing can be the proper place to note this requirement -- maybe I'm contracting a company to make this thing and all I care about is the final function. It's not my job to detail all the sub-assy parts for them.
Granted, the current standard doesn't really allow for this use of runout, but that's why we're discussing it; to see if there is even any legitimacy to trying for such a use.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
Granted, the current standard doesn't really allow for this use of runout, but that's why we're discussing it; to see if there is even any legitimacy to trying for such a use.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
pmarc
Mechanical
- Sep 2, 2008
- 3,248
Okay, say you are contracting a company to make this thing for you. Why would you like to go with the runout callout instead of clear combination of position tolerance (possibly with addition of one more datum reference) and circularity tolerance?
Please do not get me wrong. I am all for novelties and extension of principles, but only if there is really no other way to express something. Per my understanding we do not have such a situation here.
Please do not get me wrong. I am all for novelties and extension of principles, but only if there is really no other way to express something. Per my understanding we do not have such a situation here.
I agree, but if we really hold to that thinking, then there's no need for the symbols flatness or perpendicularity, since they can already be accomplished with profile of a surface (or even angularity, in the case of perpendicularity).
But I know what you're saying -- and at this point it's really just an academic discussion
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
But I know what you're saying -- and at this point it's really just an academic discussion
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
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