Total Runout tolerance Vs Position Tolerance 2

[Sybot1978]

Hi,
What is the similarity / difference between a total runout tolerance and position tolerance. Can position tolerance be used in lieu of runout tolerance

Thanks

 

[ctopher]

It depends on the part.
You may want to get a copy of ASME Y14.5.
More info:

http://www.tec-ease.com/gdt-terms.php

Chris
SolidWorks 10 SP4.0
ctopher's home
SolidWorks Legion

 

[Sybot1978]

It is a long cylindrical rod which has a pretty tight tolerance.

 

[Belanger]

Runout controls position but also the form (shape) of the part. Think of it this way: Suppose I have a part that is well-centered, but instead of perfectly round, it is slightly oval. A position tolerance might say that it's fine, but runout will check the "wobble," and thus the oval shape will be detected by runout and probably cause it to be rejected.

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

 

[dingy2]

Yes, a positional tolerance can be used in place of a runout (total or circular) tolerance but one cannot always have a runout tolerance replace a positional tolerance. Positional tolerance can be utilized on features of size relative to a datum structure not necessarily co-axial.

Total runout is applicable to small cylindrical parts with co-axial features and is usually confirmed using divider head (chuck) with a dial indicator on a stand. It confirms a combination of roundness, straightness of an axis, off center (concentricity) and straightness of a surface relative to a datum C/L.

Positional (in RFS) on the same small cylindrical co-axial part will only reflect how far the feature is off center relative to the datum C/L. That is it.

Positional (at MMC) is conducive to a checking fixture and, if built correctly, will confirm whether or not the feature is within the specification boundary (MMB).

Hope this helps.

Dave D.

http://www.qmsi.ca

 

[KENAT]

To follow on from the others.

If you're just looking to primarily ensure interchangeability (i.e. any stepped shaft will always fit in any stepped hole or the like) then position is most likely adequate.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[ewh]

Positional used in conjunction with size tolerance may suffice in place of runout.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[PeterStock]

If dynamic balance is an issue (rotating part i.e. drive shaft ect), then runout is a better choice. Otherwise I would use position.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

http://www.infotechpr.net