Continuous feature of size per Y14.5M-1994
Continuous feature of size per Y14.5M-1994
(OP)
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.
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.





RE: Continuous feature of size per Y14.5M-1994
RE: Continuous feature of size per Y14.5M-1994
I would just like to hear ideas.
RE: Continuous feature of size per Y14.5M-1994
RE: Continuous feature of size per Y14.5M-1994
Paul
RE: Continuous feature of size per Y14.5M-1994
My vote is that it absolutely can, since the total runout FCF controls location, but I have heard different opinions about that.
RE: Continuous feature of size per Y14.5M-1994
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).
RE: Continuous feature of size per Y14.5M-1994
John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: Continuous feature of size per Y14.5M-1994
Dean
www.d3w-engineering.com
RE: Continuous feature of size per Y14.5M-1994
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Continuous feature of size per Y14.5M-1994
Frank
RE: Continuous feature of size per Y14.5M-1994
RE: Continuous feature of size per Y14.5M-1994
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.
RE: Continuous feature of size per Y14.5M-1994
Frank
RE: Continuous feature of size per Y14.5M-1994
Guess which company the president of ETI had worked for before he decided to establish his own business in GD&T consultancy?
RE: Continuous feature of size per Y14.5M-1994
I agree that notes can be imperfect.
Frank
RE: Continuous feature of size per Y14.5M-1994
Frank
RE: Continuous feature of size per Y14.5M-1994
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.
RE: Continuous feature of size per Y14.5M-1994
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.
RE: Continuous feature of size per Y14.5M-1994
This isn't some "interrupted surface"
RE: Continuous feature of size per Y14.5M-1994
Frank
RE: Continuous feature of size per Y14.5M-1994
Datums. It is necessary to identify features on a
part to establish datums for dimensions locating true
positions. For example, in Fig. 5-2, if datum references
had been omitted, it would not be clear whether
the inside diameter or the outside diameter was the
intended datum feature for the dimensions locating
true positions. The intended datum features are identified
with datum feature symbols, and the applicable
datum references are included in the feature control
frame. For information on specifying datums in an
order of precedence, see para. 4.4.
5.2 POSITIONAL TOLEBANCING
A positional tolerance defines:
(a) a zone within which the center, axis, or center
plane of a feature of size is permitted to vary from
a true (theoretically exact) position; or
(b) (where specified on an MMC or LMC basis)
a boundary, defined as the virtual condition, located
at the true (theoretically exact) position, that may not
be violated by the surface or surfaces of the considered
feature.
Basic dimensions establish the true position from
specified datum features and between interrelated
features. A positional tolerance is indicated by the
position symbol, a tolerance value, applicable material
condition modifiers, and appropriate datum references
placed in a feature control frame.
RE: Continuous feature of size per Y14.5M-1994
7.2.1.3 Identifying Features to Establish Datums. It
is necessary to identify features or features of size on a
part to establish datums for dimensions locating true
positions except where the positioned features establish
the primary datum. (The exception is explained in para.
7.6.2.3.) For example, in Fig. 7-2, if datum references had
been omitted, it would not be clear whether the inside
diameter or the outside diameter was the intended
datum feature for the dimensions locating true positions.
The intended datum features are identified with
datum feature symbols, and the applicable datum feature
references are included in the feature control frame.
For information on specifying datums in an order of
precedence, see para. 4.10.
7.2 POSITIONAL TOLERANCING
Position is the location of one or more features of size
relative to one another or to one or more datums. A positional
tolerance defines either of the following:
(a) a zone within which the center, axis, or center
plane of a feature of size is permitted to vary from a true
(theoretically exact) position
(b) (where specified on an MMC or LMC basis) a
boundary, defined as the virtual condition, located at the
true (theoretically exact) position, that may not be violated
by the surface or surfaces of the considered feature
of size.
Basic dimensions establish the true position from
specified datums and between interrelated features. A
positional tolerance is indicated by the position symbol,
a tolerance value, applicable material condition modifiers,
and appropriate datum references placed in a feature
control frame
RE: Continuous feature of size per Y14.5M-1994
Yes, this is the thread, I disagree with your conclusion, I do believe you are reading too much into it to take this as a prohibition. None may be “applicable” or “appropriate”, and they will be located by datums in earlier lines.
RE: Continuous feature of size per Y14.5M-1994
RE: Continuous feature of size per Y14.5M-1994
I never said that single segment position FCF without datum feature references was prohibited.
RE: Continuous feature of size per Y14.5M-1994
Ref: Mark Foster:
In addition to my first post: "
"The only thing that is required in the 1994 standard for the position control is that there be "at least one" datum reference, and the committee eventually realized that even that statement was in error since it is perfectly possible to have a true design requirement where the orientation/location of a pattern (i.e. more than one) might need to be controlled just to each other, and not to any DRF. In fact, there are even examples of such controls in the 1994 standard." Mark Foster from:http://www.linkedin.com/groups/How-calculate-true-...
Here is the second post:
" Certainly position with no datum references would work for the control of coaxiality, but would have no effect on form. Position without datum references was prohibited in the 1994 standard (although most people did it anyway when it made sense, and there was even an example of it in the FRTZF of a composite position in the 1994 standard), but it is explicitly allowed, complete with an example of it, in the 2009 standard." from Mark Foster: http://www.linkedin.com/groups/ABC-What-1781397.S....
I don't think Mark Foster needs any introduction....
greenimi and pmarc,
Did I "save" you?
RE: Continuous feature of size per Y14.5M-1994
I know Mark - he is great GD&T expert and great guy.
I also know Alex Krulikowski - he in turn is a member of Y14.5 committee. The attached snapshot comes from his book "Advanced Concepts of GD&T", 7th edition, which bases on Y14.5M-1994 standard:
http://files.engineering.com/getfile.aspx?folder=3...
Who is right? I do not know. And this is what I have been trying to point out in this and in other threads - there is no clear answer. Fortunately, this confusion has been clarified in '09 edition of Y14.5. Unfortunately, there are still maaaaany companies following Y14.5M-1994 or even earlier versions, so this kind of debates will be happening from time to time.
RE: Continuous feature of size per Y14.5M-1994
pmarc,
In our discussion on my keyway example, IMHO, your crowning point was in essence your reference to the current datum relationship requirements in 2009, despite the fact my example and the referenced standard would be 1982, why then is 2009 not good enough to settle it, now?
Frank
RE: Continuous feature of size per Y14.5M-1994
Thanks for the information update.
Frank
RE: Continuous feature of size per Y14.5M-1994
Because what you are trying to achieve in your example (that is to locate the keyway through 2 parallelism callouts applied to its side walls AND by assigning the keyway width as secondary datum feature B) does not meet requirements defined in 2009. Your parallelism callouts do part of the job only - they orient, but do not locate, whereas for such configuration of datum features secondary datum feature (that is keyway width) shall be controlled for ORIENTATION AND LOCATION relative to primary datum axis.