Runout

[Madhu454]

Hi All,

Please see the attached file.

Genarally I have seen runout/total runout control is apllied for stepped shafts. where axis of one of the stepped part is considered as datum and the runout controll is applied to the other stepped part. Also I have seen some examples where compound datums are used.

Question is
1) Can we use total runout control for a simple shaft(No steps)? Please refer to the attached file, the toleranced feture itself a datum feature.

2) If it is a legal sceification , can any one suggest me how to simulate the datum.? can we use V-blocks? (If we use collects- the ASME says The entire suraface(datum feature) to be used to establish the datums then there is no space for dial indicator to measure)

Please help me to understand the standards better.

Madhusudhan
Mechanical Engineer

 

[pmarc]

1. Per ASME Y14.5 this callout is illegal. You can not apply geometrical tolerance to a feature that references itself in a datum portion of a feature control frame.

2. However I believe you could define datum targets A on both ends of the shaft (datum target areas or points) and assign runout control relative to A to the portion of the shaft in between the targets. Datum targets configurations could be somehow similar to the one shown for datum A in fig. 4-34 (Y14.5M-1994). And the portion of the shaft controlled by runout tolerances would be denoted by a chain line as shown in fig. 1-11.

 

[dingy2]

The drawing is illegal per ASME Y 14.5M-94 & 2009.

If you are trying to control the form of the cylinder, I would suggest that you use cylindricity. Place this feature control frame below the size tolerance and eliminate the datum.

Cylindricity has all the attributes of total runout except cylindricity is to itself. It controls straightness of the axis, roundness and straightness of the surface (size distortion) all combined.

Dave D.

http://www.qmsi.ca

 

[TheTick]

Also consider use uf bell-centers on the ends of your shaft.

 

[flash3780]

dingy is correct. Cylindricity will control the circularity of the cross section and the taper. Note that by Rule #1 (perfect form at MMC) these are already controlled by the diameter tolerance. The shaft must have perfect form at its largest diameter. Hence, the maximum out-of-roundness or taper is exactly equal to the diameter tolerance by default.

A cylindricity control would reject parts that meet the diameter tolerance, but have a cross section that more out of round or tapered than is allowed by the cylindricity control. While it's not a useless control (looking at you concentricity), I find situations where the cylindricity matters more than the diameter somewhat rare.

 

[ak762]

I would proceed from Total runout is a composite tolerance including the effects of cylindricity and concentricity.
Then you can ask yourselves concentricity between what features?
BTW last active threads looks like examination for professors

 

[DeanD3W]

I think we really should leave concentricity far from this discussion (due to "Concentricity" being that problematical tolerance aka "geometric characteristic" from Y14.5)... Total Runout is a combination of cylindricity and coaxiality is a much less troublesome way to say this.

Dean

http://www.d3w-engineering.com

 

[SeasonLee]

Dean

I am with you, Don's tip gives us a excellent explanation.

http://www.tec-ease.com/gdt-tips-view.php?q=232

SeasonLee

 

[pmarc]

1. Per ASME Y14.5 this callout is illegal. You can not apply geometrical tolerance to a feature that references itself in a datum portion of a feature control frame.

2. However I believe you could define datum targets A on both ends of the shaft (datum target areas or points) and assign runout control relative to A to the portion of the shaft in between the targets. Datum targets configurations could be somehow similar to the one shown for datum A in fig. 4-34 (Y14.5M-1994). And the portion of the shaft controlled by runout tolerances would be denoted by a chain line as shown in fig. 1-11.

The link below visualizes what I meant in point 2 of my preview post.

http://tec-ease.com/gdt-tips-view.php?q=144