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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...

Greenimi -- even though the standard's graphic doesn't have size dimensions, Rule #1 would indeed control the flatness of that surface (assuming it's a rigid part). John-Paul Belanger Certified Sr. GD&T Professional Geometric Learning Systems

Let's go with his idea and take it to its extreme -- if the surface where A1, A2, and A3 are is not toleranced for flatness (because somehow it's "forbidden"), then what controls it from being crazy bumpy? Rule #1? Your colleague is simply making stuff up. If a regular-style datum surface can...

For your two questions for me... I would say it's not illegal. For Figure 4-42, it seems that B1 and B2 are on a very small surface that is toleranced by profile. Is that illegal? Or is it OK because it includes datum B in the callout? John-Paul Belanger Certified Sr. GD&T Professional...

I might say the burden is on him to prove things (why does lack of a picture equate with the standard forbidding something?). But here are two more thoughts: --Since the datum plane is created just from areas A1, A2, A3, a flatness tolerance on the overall surface is not doing much to the...

I was looking at 2018. In 2009 it would be Fig. 4-2. But my point is that if your colleague is fine with the figure I gave, why would having targets change things? John-Paul Belanger Certified Sr. GD&T Professional Geometric Learning Systems

The ASME standard certainly shows examples where datum features are "qualified," that is, toleranced for their own accuracy to each other. Check out Fig. 7-2, where D is tagged with flatness and E is then perpendicular to D. So is this person's issue that the datums in question are formed by...

Hello from this side of the pond! This quote is from ASME Y14.5-2018, paragraph 4.2: "For uniformity, all dimensions illustrated in this Standard are given in SI units UOS (unless otherwise specified). However, the unit of measure selected should be in accordance with the policy of the user."...