Multiple secondary target points

[RLD89]

When using datum targets on a flexible part with a complex shape, there is no limit to the number of primary target points. Can the secondary have more than two target points?

 

[3DDave]

If it makes sense to use multiple directions of restraint then there is no need to limit the number of them.

 

[pmarc]

From Y14.5-2009, para. 4.20:
"In a restrained application, it is permissible to use as many datum targets as necessary to establish the datum features."

 

[SeasonLee]

There are 4 target points on secondary datum feature on Fig.B-2 Y14.8-2009.

Season

 

[Belanger]

Even in an unrestrained condition, it would be permissible to use more than the usual number of targets. The part may not contact all of them (which is why restraining is often advisable) but maybe full contact isn't needed.

Also, there are instances of a secondary datum needing less than two points of contact -- only one point.

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

 

[RLD89]

Thanks to all for the responses. It clarifies doubts I had.