Datums call out @ part center is correct? 4

[darshan84]

Please see attached image. Can i use part center to call out datums?
Please help me to understand, why i can use it.

Thanks,
Darsh

 

[ctopher]

I don't see anything attached.

Chris, CSWA
SolidWorks 14
ctopher's home
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[KENAT]

Can i use part center to call out datums?

Yes you can have a datum derived from some defined feature (such as part overall dimension) which is effectively the center plane of that feature.

thread1103-292841 and plenty of others

http://www.eng-tips.com/search.cfm?...datum&t=&h=&searchSite=1&searchArea=1&d=1&s=1

touch on this.

Posting guidelines faq731-376

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(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[darshan84]

Please find missing attachment.

 

[darshan84]

I am refering to Datum B in attached image.

 

[darshan84]

I have attached one more drawing. Please help me...

 

[axym]

Darshan84,

No, you can't use a part centerline to define a datum as shown in your examples. The datum feature symbol must be associated with a particular feature, or features.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[KENAT]

darshan84 - did you look at the links I provided?

The first response in the thread I linked had this illustration:

http://files.engineering.com/getfil...-4804-85a0-79f5f6decc97&file=datumunknown.jpg

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[Belanger]

As stated above, you can't have a datum symbol attached to a non-touchable center. There are a couple of reasons, but the main one is that we don't know exactly what center is being referred to: Is it the center plane derived from the outside width? Inside width? Middle plane of the holes' location? And so on.

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

 

[PaulJackson]

Here is a functionally blind option.
Paul

 

[SeasonLee]

Darshan84

You sure will ask why I can't use the center line as a datum feature, here is the answer for you. Even ISO GPS not allow the datum symbol place on the center line on the new standard.

http://www.youtube.com/watch?v=xbA4FrZnZVM

From the point of view on datum point (0.0,0.0) on your last post, use the hole pattern as a datum feature is a good practice as mentioned by Paul.

Season

 

[darshan84]

Thanks all....for your kindly suggestion...

 

[powerhound]

Just a point of interest. Your callout for Datum C is also wrong for the reasons stated above.

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
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