Axis parallel to plane

[Edgarchen]

Hi All,
I design a cylinder with a machined flat surface and I want to make sure the axis of the cylinder is parallel to the machined plane. Is it okay to define that with parallelism?
I can find the attachment for detail.
Thanks in advance.

 

[CheckerHater]

Ask yourself: is [A] axis of inner or outer cylindrical surface?

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[DeanAllen]

This is basically correct. The cylinder dia should be on the drawing. The datum on the end of the cylinder dimension. This then shows the datum as being the centreline of the cylinder. Putting the datum on a centre line is not preferred as potentially it could be difficult to understand how to get the centreline if you have multiple different diameters.

 

[powerhound]

This is actually not correct at all. It's not that putting the datum feature symbol on a centerline is "not preferred". It's that putting a datum feature symbol on a centerline is expressly prohibited by ASME Y14.5.

If this is supposed to be an ISO drawing then all bets are off. I don't know if ISO prohibits it or not.

Your explanation and the way you described the remedy is correct though. I guess I just don't think it's a good idea to leave any idea that something like this could be okay. Saying it's "not preferred" implies that it is okay to do, just not preferred.


John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[Belanger]

ISO used to allow that, I believe, but now they too prohibit the datum symbol from being attached to a center line.

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

 

[Edgarchen]

Hi, thanks for all your feedback. I will make the datum A attach to the inner cylinder diameter.

 

[DeanAllen]

Hi gents, I think you misunderstand my comment slightly. The datum should appear on the end of the dimension which indicates the centre or median plane of that feature. I am used to the ASME standard, BS308, BS8888, ISO1101, ISO 8015, envelope rule, differences between the standards as I teach this to aerospace design engineers at work. The main thing with all drawings is that it is clear for the manufacturers and they understand the tolerances involved. In my experience they don't even know rule one of the ASME standard and this is now opposite to BS8888 since the 2008 version came out.

 

[greenimi]

The main thing with all drawings is that it is clear for the manufacturers and

I would add....and the inspectors/quality personnel.....

In my experience they don't even know rule one of the ASME standard

Damnit, I have to agree with you here............