DATUM CALLOUT

[learningchecker]

When 2 surfaces are to determine one datum plane, how is it called out on a design drawing? The two surfaces are in line, but interrupted by a rib (wall). Could I put a Datum A Symbol with "2X" or "2 SURFACES". Datum targets? Is there more than one solution. I understand an extension line is not acceptable for GD&T. Material is MIM (Metal Injection Molding).

Thank you.

 

[pmarc]

First question, as usually, is: which standard and which version of the standard governs the drawing?
Assuming it is Y14.5-2009, fig. 4-23 is what you probably need to look at first.
Datum targets can also be used, but I would use them only if some portions of the interrupted surface are acting as datum features.

 

[KENAT]

Simplistically If working to ASME Y14.5M-1994 I'd start out at section 4.5.7.1 and take a look at 6.5.6 too.

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[learningchecker]

The standard is ASME Y14.5-2009 and figure 4-23 is exactly what I need. Darn on missing it. Thank you very much.

 

[KENAT]

learningchecker - I'd still take a quick look at the section on coplanarity as it may change just how you decide to spec it.

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[learningchecker]

KENAT......I will look at the section on coplanarity. Thanks.