Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

Register Log in
  • Congratulations waross on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Continuous feature of size per Y14.5M-1994

Status
Not open for further replies.
pmarc

pmarc

Mechanical
Sep 2, 2008
3,171
I guess my general question is short: "How would you specify continuous feature of size on a print governed by Y14.5M-1994?"

Let's say I want to control total runout of an external cylinder containing an interruption (O-ring groove for instance) relative to a datum axis. How would you indicate on a drawing that both parts of the cylinder, in addition to the total runout requirement, must not violate single MMC envelope defined by Rule #1?

Thank you.
 
Replies continue below

Recommended for you

Sort by date Sort by votes
No, I am not.
I would just like to hear ideas.
 
Upvote 0 Downvote
Zero position at MMC should tie up two cylinders together (providing they are dimensioned as “2X DIA”), but it doesn’t seem very elegant. I only have copy of 2009, so not sure about what tricks are permitted and what are not :)
 
Upvote 0 Downvote
GM in their USCAR exception to ASME Y14.5 used the term "interrupted" for a continuous that was otherwise interrupted.
Paul[tt][/tt]
 
Upvote 0 Downvote
I agree, zero position at MMC would do the job. However, my next question would be: "Is stand-alone zero position at MMC callout with no datum feature references acceptable callout per '94 version of the standard?". I mean, can this callout live without additional positional FCF controlling location of the interrupted cylinder relative to datum axis?

My vote is that it absolutely can, since the total runout FCF controls location, but I have heard different opinions about that.
 
Upvote 0 Downvote
Paul,
Yes, I am aware of GM addendum. The thing is the company I work for does not have such technique specified in its own addendum, thus there is nothing to use as a reference, thus this would have to be explained directly on the drawing (in notes area perhaps).
 
Upvote 0 Downvote
I had originally considered offering the zero position at MMC concept but since the OP stated runout, I figured the response would be "I asked about runout, not position." Since the concept is viable, I would say that it's a good option; however--unlike runout--it does not control form. That would be controlled by rule #1.

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
 
Upvote 0 Downvote
I would just use a flag note that says something like "ONE TOTAL RUNOUT TOLERANCE APPLIES TO BOTH CYLINDRICAL SURFACES AT ONCE (INTERRUPTED SINGLE FEATURE COMPRISED OF TWO SURFACES)".

Dean
 
Upvote 0 Downvote
Agreed -- when in doubt, simply write a note to explain what you want. That's always been the solution when a geometric tolerance might not be clear or needs to be tweaked.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
 
Upvote 0 Downvote
I am with JP, notes may not prefered, but, have always been an acceptable form of drawing comunication.
Frank
 
Upvote 0 Downvote
Chain line is normally used to “limit” the feature the control applies to, but does anyone think it can be used to “extend” the feature?
 
Upvote 0 Downvote
Thanks Guys. I will suggest putting a note on the drawing - the least risky option (if done properly).

As for use of chain line -- I personally do not think it is more advantageous in comparison to placing zero positional FCF without any datum references. Besides, para. 2.7.5 of Y14.5-2009 states: "extension lines by themselves do not indicate a continous feature". I would not like to introduce something that from the very beginning (although governed by the old standard) is in conflict with the newer one.

Thanks again.
 
Upvote 0 Downvote
I had noticed ETI was pushing the "INTERUPPED FEATURE" concept in their books.
Frank
 
Upvote 0 Downvote
You know why, Frank?
Guess which company the president of ETI had worked for before he decided to establish his own business in GD&T consultancy?
 
Upvote 0 Downvote
No, I did not, Thank you, pmarc
I agree that notes can be imperfect.
Frank
 
Upvote 0 Downvote
Actually, before 2009, I would have tried to make due with the term "COMMON ZONE", with the idea that it was at least defined in a "standard" (ISO) and therefore some may already know it.
Frank
 
Upvote 0 Downvote
Pmarc,
I just have a short question for you (now that the note option has been decided to be the solution for your issue)

If you callout total runout wrt A-B on the first part of the cylinder and name this datum feature A and after that for the second part of the cylinder another total runout callout to A-B and name this datum feature B, why this option wouldn’t be legal in 1994 and why will not satisfy the requirements from the OP?

Or I would say, instead of total runout you can use position wrt A-B (datum feature A) for the first segment of the cylinder and again position to A-B for the second part of the cylinder (datum feature B)

What am I missing? Probably what I am proposing is more an academic/intellectual discussion than a real design requirement , but I would like to know your opinion.

Thank you pmarc

By the way, in my opinion is that position with NO datum was prohibited in the 1994 standard (I know you will say that Fig. 5-51 and Fig. 5-53 in 1994 state otherwise and contradict the above statement). It’s prohibited, but even the standard show it.
 
Upvote 0 Downvote
greenimi,
Imagine that the interrupted feature is divide into two portions and that both of them are at MMC everywhere along their axes. Per Continous Feature concept they have to be perfectly coaxial then, because they are tied by MMC envelope defined by Rule #1, correct?

Appying total runout or position callout wrt to A-B (where A is one portion of the interrupted feature, and B is the second portion of that feature) allows both portions to have coaxiality error equal to the tolerance value specified in position or total runout FCF even if they are at MMC. So these are two geometrically different requirements.

Your last statement (about illegality of positional callout without datum feature references in Y14.5M-1994) is exactly the reason why I decided to go with a note. I am saying that stand-alone position without datum feature references is legal (or at least is a reasonable extension of principles), but because other drawing readers may think otherwise, and I am not able to prove they are incorrect, I prefer to choose solution as clear as possible for everyone.
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

CTengIS
  • Question
Irregular Feature Of Size as Datum Feature on CMM
2
Replies
20
Views
8K
CTengIS
CTengIS
jnelson33
  • Locked
  • Question
Internal Planar Continuous Feature 2
Replies
6
Views
210
Burunduk
Burunduk
Azeemsha
  • Question
How to properly show compound angles of a feature using GD&T?
Replies
9
Views
4K
jassco
jassco
Diametrix
  • Locked
  • Question
Can FCF be attached to the extension line of a cylindrical feature of size?
Replies
9
Views
143
Burunduk
Burunduk
Ali121
  • Locked
  • Question
Inspection of individual piece parts feature in the assembly 2
Replies
8
Views
240
drawoh
drawoh

Part and Inventory Search

Sponsor

Back
Top Bottom