total runout on a cone --again

[greenimi]

Per Y14.5-2009 total runout applied to surfaces around an axis will control...see bellow

9.4.2.1 Applied to Surfaces Around an Axis. Where
applied to surfaces, constructed around a datum axis,
total runout may be used to control cumulative variations
such as circularity, straightness, coaxiality, angularity,
taper, and profile of a surface.

Per the draft version:
12.4.4: a.) Where applied to surfaces constructed around a datum axis, total runout controls cumulative variations such as circularity, cylindricity, straightness and location (coaxiality) of a cylindrical surface.

The magic word in the last sentence is "cylindricity"

Should I understand that by adding "cylindricity" to the definition of the totaal runout then the door of using total runout to a cone (with, of course, basic angle implied) is permanently closed?

And if yes, do you think it is a good idea?
Yes? No? maybe? Why yes? Why no? Why maybe?

 

[3DDave]

They dropped angularity and taper, it looks like.

Why not define it as:

Total runout limits the variation in distance from a datum axis at each combination of angular and axial location of the identified surface. This can only be applied to nominally cylindrical surfaces.

No need to compare or contrast with other tolerance descriptions.

The second definition for total runout can be eliminated as it is already covered under the perpendicularity tolerance.

The main benefit is to inspectors, who are no longer obligated to set their dial indicator traversal mechanism at a precise angle; they can just leave it parallel to the fixture axis. I presume that the tapers will have to be covered under profile.

 

[greenimi]

Speaking about the inspection method in 2009 a disclaimer is present
9.2 Runout :
"NOTE: The figures in this Section use measurement techniques to explain the tolerance zones. It is neither the intent nor within the scope of this Standard to define measurement methods."

I cannot find this note in the draft. I am not saying is not there, I am saying I cannot find it .

Or the intent of the revised Y14.5 will be altered to be "more friendly" to the inspection methods... same way ISO is "favorably disposed' to the inspection method. I remember some discussions on the forum and the suggestion that Y14.5 is trying hard to distance itself from inspection method and manufacturing/process and stick with function.

 

[greenimi]

Looks like 2009 examination has been moved back to January 2017 (from September 2016)

The exam currently available is to the 1994 edition of the Y14.5 standard. The ASME Y14.5 testing committee has been actively working on developing an exam to the 2009 Edition. The projected availability for the 2009 exam is January 2017.

 

[JNieman]

To me, when a list is preceded by "such as" - it does not mean they are all simultaneously controlled, but they can all apply depending on context. I MAY BE WRONG but isn't that what 'such as' implies? That it /can/ but not necessarily /shall/ control all those listed items?

If it's a cylinder, it will control cylindricity; if it isn't, it wouldn't. Maybe?

Looking at a couple grammarian references, I am no closer to a point-of-fact regarding "such as" unfortunately.

ETA: I hate picking at word use like this... the statements should be so clear as to not need to do so. I feel like I'm asking what the definition of "is" is.

 

[AndrewTT]

I hope the 2009 test is available before the new version of Y14.5 comes out. The 2009 test has been pushed back a few times now, I believe.

 

[3DDave]

They should drop it. Based on the example materials I've seen it is primarily a parrot test - depending on memorizing the exact phrases, phrases which the Committee changes the content of and seems will continue to alter, from version to version.

Of three who I know took and passed the test, only one could solve more than a simple example and one continued to depend on suppliers to avoid making parts that would be acceptable, but would not fit. It tires me when someone says 'they won't use all that tolerance' as an excuse.

I decided to drop the notion of the test when the online 'how smart are you' teaser from ASME had the wrong answer because it failed to include datum shift in their calculation. Rather than correcting the teaser, they took it down.

For those who study hard and make the effort and can use it as a cudgel to make better drawings and parts - go for it.

For the preening pass-and-forget crowd, I think they need to be left out to dry.

As I've mentioned before, the real solution is to have decent analysis software that impartially and accurately evaluates the likely outcomes and is available to those who know nothing about tolerance analysis innards at all, any more than a spreadsheet user needs to know how floating point math is managed in a computer.

My major annoyance is with the majority of users who would not think they learned how to program by reading the reference manual, but don't seem to get that dimensioning and tolerancing is programming. Instead they argue 'their' interpretation and it gets into a mix of bullying and outright sabotage.

 

[pmarc]

greenimi,
Look at fig. 11-38 in the draft. A dynamic profile is something that will be possible to use instead of total runout.

 

[greenimi]

Thank you pmarc.
Still not very clear, in my own head, how the dynamic "delta" symbol affect the tolerance zone, but I know you discussed this symbol on this forum, so I'll go back and read and re-read and maybe, just maybe, will understand it.
I know you will say: " I can expalin it to you, but I cannot understand it for you", so back to school for me!
Thank you again