Contoured Datum : Fig 4-29 of 2009 Std

[Madhu454]

Hi,
I am referring to figure 4-29 of ASME Y14.5-2009 standard.
Could anyone help me to understand the concept clearly.

1) The datum feature "B" is a semicircular surface (feature). Since there is no opposed surface to this, it is not a feature of size, But in fig (b) Datum B is identified with Max Material modifier. Can the "M" modifier be identified to datum feature "B" since it is not a FOS.

2) What is datum feature "B" here? Is it the Axis?
Is it the axis derived from AME of datum feature "B"?

 

[Belanger]

Yes, one of the new items in 2009 was the ability to add MMB to a datum that's not a feature of size. That's covered in Figs. 4-29 through 4-31. The picture shows the theoretical datum as the axis.

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

 

[Madhu454]

Thank you John-Paul