ISO datum scheme 1

[SeasonLee]

I have a part with ISO standard, please see the attached for details.

There are a lot problems on this drawing, let's concentrate on the datum setup scheme. Have you ever seen this G-H reference datum before? G and H is two holes feature located at the corner diagonally, I believe it would be two hole pattern as a datum in ASME standard, how do you think.

Thanks for your inputs

 

[CheckerHater]

I am surprised you have no problem with the way datum features are identified, neither ISO or ASME, or datum C symbol attached to the axis.

Datum letters separated by dash mean neither takes a precedence just like in ASME (Some ISO experts may be able to point out subtle differences though)

 

[SeasonLee]

Thanks for your comments, CH.

I can find out lot of examples with multiple datum features in 1994 or 2009 standard, I know what is the
meaning of datum feature reference letters separated by a dash, sorry for I didn’t clearly specify
my question.

How will you setup the DRF on the position callout |pos|0.04|G-H|, is this legal in ISO standard?

Season

 

[pmarc]

This may help to find an answer to your last question:

http://files.engineering.com/getfil...-3e0d-4be0-bed7-ebc14ab34f5f&file=ISO5459.png

Of course I assume that no diameter symbol before 0.04 is just a typo.

 

[SeasonLee]

Great, this is what I need to know. Thanks pmarc.

Season

 

[pmarc]

Season,
I am afraid that this issue is just a tip of the iceberg.
I am looking at datum feature C and I don't envy you.

 

[SeasonLee]

pmarc

The concept of a common datum establishing from two parallel cylinders is just looks like a two hole pattern as datum feature in ASME, am I right?

Season

 

[pmarc]

I would say so.

 

[axym]

pmarc,

In the ISO 5459 excerpt, the two associated cylinders have variable diameters. Would you say that the two diameters are individually variable, or that they must vary together?

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[pmarc]

Evan,
Here is different figure from this standard. I believe I know what you are thinking about

http://files.engineering.com/getfil...16-471e-a3af-eb14ddd44572&file=ISO5459(2).png

 

[axym]

pmarc,

Yes, that's it.

Do you think that the two cylinders can be fitted (i.e. minimized) in a unique way? It always seemed to me that there is more than one solution.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[pmarc]

I can imagine that if physical datum feature simulators were used to simulate common datum axis for this part, the configuration shown on fig. C.26.b could look different, because this figure seems not take into account any physical interaction between datum features and their simulators.

 

[axym]

pmarc,

It does seem that different common axes could be generated. One simulator could be loosened and the other simulator tightened, resulting in a different relationship between the part and the datum axis.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca