GD&T Basic needs in aspect of application.

[enggasw]

HI ALL,

In GD&T how can we apply certain values as default as there is no critical points to mention. are there any guidelines for applying values also in aspect of manufacturability.​

Most of my drawings don't have any criticality to mention on tolerance value zone. in those situations, how can I decide the values as inputs.

Thanks in advance.

 

[Tmoose]

ISO 2768 has 3 grades of machining tolerances based somewhat on good workshop practice.

Assigning tolerances without understanding the component's and the assembly's functions can lead to big trouble.
[ul]
[li]Overly costly parts[/li]
[li]Components not Assembling correctly [/li]
[li]Assembly not functioning as required[/li]
[/ul]

 

[Wuzhee]

The most basic is a profile fcf in title block which applies all-over (ASME).

 

[Belanger]

Tolerances should be as large as possible while still allowing the part to function in the desired manner. Other than that, there is no advice to give since your functional parameters are undefined.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[Burunduk]

This is the current ISO standard that is probably your best shot:
ISO 22081:2021

 

[3DDave]

Use really big values. That might uncover some critical points. 10 mm or 2 inches is usually enough.

You will get plenty of detailed information after that.