Dimension drawing standardization completed

Discussions about the development of the TechDraw workbench
renatorivo
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Location: Torino - Italy

Re: Dimension drawing standardization completed

Postby renatorivo » Wed Oct 16, 2019 8:09 pm

My book says: "The reference lines start at the end of the element to be dimensioned. It is also possible to detach them by a small measure (about 8 times the thickness of the line used)". This with reference to the UNI ISO 129-1 standard, I do not know if referred to the 2018 or previous version.
However, all the examples are with the lines attached. So I think that using the ISO standards we need a valid reason to leave a gap.
Does anyone have the original ISO 129-1: 20018 standard?
tpavlicek
Posts: 27
Joined: Sun Jan 07, 2018 2:15 am

Re: Dimension drawing standardization completed

Postby tpavlicek » Fri Oct 18, 2019 8:54 am

Hi to all,

the ISO 129-1:2018 says in section 5.5, paragraph 6:
It is permissible to have a gap, eight times the extension line width, between the feature and the beginning of the extension line. Gaps can be used with any terminator.
Therefore yes, the gap is allowed. From my point of view, it is not a very big deal to add something like "Extension Line Gap" View property to the dimension, prefilled according to the selected standard - i.e. False by default for ISO, True by default for ASME.

The question is: Can you imagine a situation, when one extension line needs the gap, while the other one shall not have it? Or is both gapped/attached treatment sufficient? As you can see, I'm rather lazy and my aim is to flush everything in a single commit ;-)

Kind regards,

Tomas
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wandererfan
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Re: Dimension drawing standardization completed

Postby wandererfan » Fri Oct 18, 2019 2:06 pm

tpavlicek wrote:
Fri Oct 18, 2019 8:54 am
The question is: Can you imagine a situation, when one extension line needs the gap, while the other one shall not have it? Or is both gapped/attached treatment sufficient? As you can see, I'm rather lazy and my aim is to flush everything in a single commit ;-)
%s/lazy/efficient/ :)

Just an opinion, but all the dimensions on a page should follow the same rules.
tpavlicek
Posts: 27
Joined: Sun Jan 07, 2018 2:15 am

Re: Dimension drawing standardization completed

Postby tpavlicek » Fri Oct 18, 2019 10:40 pm

wandererfan wrote:
Fri Oct 18, 2019 2:06 pm
Just an opinion, but all the dimensions on a page should follow the same rules.
Sorry, I probably did not explain well what I mean. Sometimes it really make sense for ISO drawings to create a small gap between the piece and the extension line. My question meant: Is there a case for a single dimension, when the gap should be made between the piece and e.g. the extension line from the dimension starting point, but not between the piece and the extension line from the dimension ending point? This would mean to split the setting into actually 2 independent values (let's say "Start Gap" and "End Gap").

Another "issue" which comes to mind is, if you are dimensioning for example a circle. If the circle is big enough, the 6x line width ASME gap between the opposite points on the circle and the extension line ends is not sufficient to create a visible break. In such a case it would make sense to actually provide the "Gap Size" in distance units, instead of fixed line width multiple. Did anyone encounter this imperfection as a real problem?

Kind regards,

Tomas
aapo
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Joined: Mon Oct 29, 2018 6:41 pm

Re: Dimension drawing standardization completed

Postby aapo » Sat Oct 19, 2019 5:04 pm

tpavlicek wrote:
Fri Oct 18, 2019 10:40 pm
Sorry, I probably did not explain well what I mean. Sometimes it really make sense for ISO drawings to create a small gap between the piece and the extension line. My question meant: Is there a case for a single dimension, when the gap should be made between the piece and e.g. the extension line from the dimension starting point, but not between the piece and the extension line from the dimension ending point? This would mean to split the setting into actually 2 independent values (let's say "Start Gap" and "End Gap").
I would certainly like that kind of degree of freedom, but I'm not sure if it's worth the effort. For me, as a user, the main convenience would be a possibility to switch between a gap and no gap for the whole dimension. If I've understood correctly, the main points said in this discussion are:
  • The default for a dimension should be as close to the standard as possible when the dimension is created, whatever the current standard is
  • When the standard for a dimension is changed to some other standard by the user, all the related dimension options for that dimension should be reset accordingly, to the values of the standard defaults.
  • User may be able to change certain aspects of the dimension after it's created with its default standard-obeying values
Also, currently, a user can freely select different standards for different dimensions in a single drawing. This does not make any sense, but at least I like the freedom of possibility to do stupid things! :D

Another "issue" which comes to mind is, if you are dimensioning for example a circle. If the circle is big enough, the 6x line width ASME gap between the opposite points on the circle and the extension line ends is not sufficient to create a visible break. In such a case it would make sense to actually provide the "Gap Size" in distance units, instead of fixed line width multiple. Did anyone encounter this imperfection as a real problem?
I have noticed this issue before, but at least for me it hasn't been a problem. I mostly use the inner diameter dimension placement for big circles, anyway. Maybe it might be a problem for someone else, it's difficult to say.