outside surface breaks

[kaptn35]

If I had a break in a outside surface that is not my established datum plane for dimensioning does ANSI require a 2X in front of the dimension?

example: If I had a sheetmetal rectangle piece 3.00 high by 4.00 long. Along the 3.00 high dimension was a slot out thru cutout of some sort. Would I have to dimension the 3.00 height as 2X 3.00 because there is now a separated surface? or is it assumed to be 3.00 high because its an outside surface?

According to page 100 in ANSI Y14.5 1982 fig 183 there is a 2X 8.6 dimension in the right view on a broken surface. So would this pertain to an outside surface that was broken?
I would think that if you establish the bottom surface as your datum dimensioning plane that it would. But if your dimensions came from the top then it would not.

 

[ctopher]

Can you show a pic? I'm a little confused.

Chris
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[KENAT]

kaptn35

Now you explain more clearly then if I understand correctly you probably need the 2X, or you need to extend either phantom or dimension leader line across the 'gap'. I've been using the 94 version of the standard though, not the older one.

If your dimensions came from the top then you probably need to specify some kind of coplanarity.

See my attatched sketches for several schemes that may I believe be appropriate depending on function etc. (I added to parrallellism fcf to illustrate how to reference the datums, they aren't directly related to your question and are labelled as examples)

I'm sure more experienced members will weigh in on my sketches and point out any errors, just please note I do invoke 1.1.4 of ASME Y14.5M-1994.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at

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

 

[KENAT]

Question was originally asked on thread174-229193

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at

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

 

[drawoh]

kaptn35,

I would apply the 2[×] to my dimension. That way, you explictly control both features. Clarity is good.

ASME Y14.5M 1994 Section 1.9.5 says that that repeated features may[ ]be specified with an X. The use of "may[ ]be" is slightly ambiguous, in the context of your question. An alternative would be to separately dimension each side of your part.

JHG

 

[ewh]

...or do as shown in KENAT's examples and draw an extension line between the two features, omitting the "2X". Still no ambiguity.
Many ways to clearly define the same thing...

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