[resolved] opinion wanted: disable tolerances when 'Theoretically exact' is True

Discussions about the development of the TechDraw workbench
User avatar
uwestoehr
Posts: 2174
Joined: Sun Jan 27, 2019 3:21 am

[resolved] opinion wanted: disable tolerances when 'Theoretically exact' is True

Postby uwestoehr » Mon Jan 11, 2021 2:15 am

When dimensioning one can mark dimensions as being theoretical exact, maybe to use them as reference of for calculations. TD supports this with the property "Theoretically exact". When this is True, a frame is drawn round the dimensions.

But at them moment we also allow this output:
FreeCAD_yzpHH9NKGa.png
FreeCAD_yzpHH9NKGa.png (854 Bytes) Viewed 385 times

This is weird since it contradicts the idea of the theoretically exact value. So when a dimension is theoretically exact it cannot also have tolerances. I googled around and had a look in the norms and I could not find a case where one has a theoretically exact dimension with tolerances specified.

However, before I "fix" this, I would like to hear if there are arguments that tolerances + theoretically exact is necessary.
Last edited by uwestoehr on Tue Jan 12, 2021 12:37 pm, edited 2 times in total.
davidosterberg
Posts: 234
Joined: Fri Sep 18, 2020 5:40 pm

Re: opinion wanted: disable tolerances when 'Theoretically exact' is True

Postby davidosterberg » Mon Jan 11, 2021 6:13 pm

I say fix it, adding tolerance to a TED makes no sense
aapo
Posts: 304
Joined: Mon Oct 29, 2018 6:41 pm

Re: opinion wanted: disable tolerances when 'Theoretically exact' is True

Postby aapo » Tue Jan 12, 2021 11:17 am

Agreed. Probably the best way to fix it is to simply skip printing the tolerances whenever "Theoretically exact" is selected. It seems to me, that there should not be tolerances with theoretical dimensions in any cases, classical or GD&T. Instead, GD&T rules and additional tolerancing should always be used for theoretically exact dimension tolerancing. And, since we now have a rudimentary support for GD&T boxes, this should be ok to be fixed.

https://www.globalspec.com/reference/43 ... dimensions
User avatar
uwestoehr
Posts: 2174
Joined: Sun Jan 27, 2019 3:21 am

Re: opinion wanted: disable tolerances when 'Theoretically exact' is True

Postby uwestoehr » Tue Jan 12, 2021 12:37 pm

aapo wrote:
Tue Jan 12, 2021 11:17 am
Agreed.
Thanks, so I will make a PR fixing it.
aapo
Posts: 304
Joined: Mon Oct 29, 2018 6:41 pm

Re: opinion wanted: disable tolerances when 'Theoretically exact' is True

Postby aapo » Tue Jan 12, 2021 12:42 pm

uwestoehr wrote:
Tue Jan 12, 2021 12:37 pm
Thanks, so I will make a PR fixing it.
Thanks for working on TD! :D