design flange

[Andrea1989]

Good morning to all,
I'm designing two circular flanges with 8 holes.
the first is a flange to weld with female on which to accommodate a tube.
the second is a blind flange that will act as a melt once bolted to the first.
my question is related to the localization tolerances of holes on the blind flange; While on the welding flange I can use as a primary reference the sealing surface and as a secondary reference the tube housing hole axis, for blind flange, what should I use as a secondary reference to locate the 8 holes?

thanks to all those who will help me

 

[MassiVonWeizen]

Is yours a question that has relevance with creo?
the answer however is: the outer diameter

 

[Andrea1989]

so I take as secondary reference the outer diameter (i.e. the axis) of the blind flange?
when processing the turning machine can use it as a reference for holes?

the design is made with creo, but I think I still wrong the tag to the conversation. I'm sorry I'm the first guns.

 

[MassiVonWeizen]

when processing the turning machine can use it as a reference for holes?

bhé depends on how you want to perform these holes. and how the piece is made.
do it on the lathe only if you have a mobile and multifunctional tower then at least a semi automatic lathe; the spinner that has on the self-centering spindle the flange already has its zero.
if as often happens you don't do it on the lathe, but on milling or on drill you just have to tascate the outer diameter and move accordingly.
Whereas the two flanges will be connected with bolt the holes will have at least 1 or 2 mm of play therefore quite comfortable.
the outer diameter of the two flanges has no functionality therefore even if you make the out axis holes of 5 mm do not compromise the seal that will be given by a seal housed only on one of the two flanges; Of course the smell will be bad to see.
the only thing that matters is the diameter of interasses.

 

[Andrea1989]

very clear, thank you very much for the help

 

[MassiVonWeizen]

However, it is better to attach an image even if the question is trivial. an image immediately clarifies the context of what is spoken.

exist commercial flanges for almost all commercial pipes https://www.oppo.it/tabelle/a_elenco_tabelle.html

 

[Andrea1989]

Okay, I thought that given the simplicity of the case was not necessary. in the future I will

in my case I have to use an ad hoc sized flange due to constraints in assembly with other pieces
Thank you.