I agree 100% with all the replies. There's really no general rule that can be applied here. The drawing should be designed to guarantee fitment and function with the widest tolerance possible. The idea of increasing a tolerance just because something is safety critical doesn't really make sense...
greenimi, I believe using SZ CZ alone is ambiguous because there's no rule that say's which holes form which pattern. My suggested notation would be:
It complies with this clause a(1) of Rule E from ISO 5458:2018 which specifies allowable methods for indicating a multi-level pattern. There are...
I like the CT+E notation because it guarantees fitment of a pin between the holes - if that's the design intent. You could get away with a single CZ with an 8x pattern if there's no functional need to guarantee fitment of a pin.
4x / 2x ⌀6 CT (E)
|POS| ⌀0.3 CZ | A | B |
Daniel, if you're interested in learning ISO GPS I'd recommend reading "Technical Drawing for Product Design by Stefano Tornincasa". It contains - in my opinion - a great functional overview of the ISO system and also covers how it differs from ASME. It explains design intent and use cases...
Garland,
This is an excerpt from ISO 5458 5.4.3 Rule C: indication of a single indication pattern specification:
I believe perpendicularity with a CZ modifier could be used to create an internal position constraint on a pattern on holes. I believe the reason you don't see it used that way is...
Garland23, this comes back to my point that position is less ambiguous because it's better defined. My initial thoughts were the same as yours - that is can't be applied to perpendicularity. But I re-read ISO 5458 to respond to the question and saw that CZ applies an internal constraint that...
Auxcron, it depends on the function as to whether your application of tolerances is correct/optimal, but what you've done is valid.
I believe the use of perpendicularity would have the same effect as position since the CZ modifier internally creates a location constraint for the pattern. That...
Hole tables are a common way to achieve this. Most CAD software should be able to do it automatically. ISO 129 provides the following example of "Tabulated repeated features":
Ryan.
"part to be free from machining burrs" is not a defined term. ISO has a standard for defining edges, ISO 13715. The edge break symbol looks like this and defines a tolerance zone for edges.
.
Ambiguous drawings get ambiguous results.
Ryan.
There's a few problems here. Firstly for a combined flatness tolerance zone, the nominal surfaces must be coplanar (See ISO 5458 section 1). Even if they used an applicable constraint such as position, the control is attached to the extension line of the bottom face and as such only applies to...
In response to Burunduk's enquiry on where this type of control is defined - The example in Figure B.14 is a combination of a compound feature per ISO 1101 section 9.1.4 and the application of Rule C of ISO 1660 as posted above. The tolerance limits are a tube formed by an infinite series of...
There's no problem with using datum A as a the primary datum on the 45.25 hole. Datum A will constrain perpendicularity of the hole to the datum plane. Datum B will then constrain one translational degree of freedom of the hole.
Ryan.
UF can always be used instead of CT, but not the other way around. There's plenty of these refinements in the ISO standards and I think their value is questionable.
Profile of a surface is allowed and means the same thing as using flatness. I personally prefer to use flatness because it reduces ambiguity by explicitly defining the surfaces as nominally flat & coplanar.
Ryan.
