Studying for the Y14.5 certification exam would be an excellent way to learn or review some of those topics. People think that the test is all about GD&T, but the exam covers those early chapters where some of the things you're talking about are detailed. (Granted, it's based on the older 2009...
Chris, just a small nit-pick... While I agree that the tolerance range is .145 - .150, the target value is not .150 (according to ASME Y14.5). In the standard, paragraph 4.1(q) says "UOS by a drawing/model note or reference to a separate document, the as-designed dimension value does not...
I simply said I don't know offhand (without digging up the doc and finding a quote). It was in reference to your saying that "simultaneous requirement is not default in ISO."
Since that's not the immediate topic, I just punted and said that we should assume my first sketch to be ASME...
Greenimi, I don't know if that's true about ISO. Perhaps you're thinking about size dims, which don't serve as location (unless the modifier CT is shown).
But to be safe, let's just say I meant the first pic to be ASME style.
Pmarc, yes I purposely left off a secondary and tertiary datum to...
A very interesting thread. I've seen CZ used is several capacities, but I never thought much about the perpendicularity application.
Garland23, does the attached picture sum up your question? (Assume datum feature A is the main face, and TEDs would be given, etc.)
John-Paul Belanger...
Most likely, a single datum isn't sufficient. As Burunduk suggested, you'd probably want to identify one of the large faces as the primary datum feature, and then yes, the current datum feature A (perhaps rename it as B) should be qualified to the large face with a perpendicularity control...
The question pertained to the sketch that was provided.
Datum B plays no role in that stack; it's all about how the two main faces interact with each other.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
I was referring to the amount of leaning, but actually both. Notice that datum feature B is the left side. What would that have to do with stacking the parts in the manner shown?
Nothing -- so the stack for leaning is really about parallelism. That's controlled by the perpendicularity...
But... if the height tolerance (±y) is smaller than 0.02 total, then it would control the leaning-tower stack result, rather than the perpendicularity numbers (because that becomes an implicit parallelism control).
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
I didn't watch the entire vid yet, but I notice a total runout tolerance with the MMC modifier. Ouch -- good luck with that.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
If you're asking about using that term as a specification on a drawing, the answer is that it's usually discouraged. According to the ASME Y14.5 standard:
"The drawing should define a part without specifying manufacturing methods. Thus, only the diameter of a hole is given without indicating...
The options you propose all sound valid, but they will have significant differences. That's because parallelism is merely an orientation control; it doesn't control form (roundness/circularity/cylindricity). If you go with cylindricity, that's merely a form control (doesn't control parallelism...
It depends on whether the callout is the symmetry symbol or the position symbol (you used both terms). Also, it might depend on which tolerancing standard the drawing subscribes to (ASME or ISO).
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
Greenimi -- yes, that certainly would apply (and Rule #1 would control form, if nothing else).
But he might not even like the general profile idea, if he's that stuck on the notion that any tolerance on the surface is illegal!
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric...
If a part's function means that it's only being contacted at selected regions (thus the datum targets), then it's plausible that there need not be any explicit form or orientation tolerance to supplement those surfaces.
But it's a HUGE stretch to say that an explicit form or orientation...
