Same dimension value, different feature

[AaronRodgers]

I am familiar with using the notation 2X <dim> when features are repeated. How do you dimension a part which has two different features with the same value such as in the picture? This is a section view of a round part. I am trying to decide how to make it clear that both the Ø2.750 and the Ø2.562 are to be 29/32" long.

 

[SeasonLee]

You may simply add a hole depth symbol followed 29/32" on the ID Ø2.562, as shown on Fig 1-34~1-38 1994 standard (or Fig 1-36~1-39 on 2009 standard).

SeasonLee

 

[AaronRodgers]

Yes, I think I will do it that way. Thank you.

 

[MechNorth]

The dimension is fine the way it is. Simplifying the Y14.5 standard somewhat, "if it appears centered, coplanar, coaxial, then it is unless you dimension it otherwise". There is no indication that the two features are at different levels, therefore they are not.

Jim Sykes, P.Eng, GDTP-S
Profile Services

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[drawoh]

AaronRodgers,

On similar drawings, I have applied a 2X to your 29/32 dimension. This makes it clear it applies to two features.

Another way would be to have a separate dimension in the middle of the view, showing the depth of the hole. On drawings like this, I like to do half sections. I dimension the external features on the non-section side, and the internal features on the other.

JHG

 

[DanStro]

If one of the features needs to be controlled differently than the other I will usually put something like "(dia2.5620/2.5615 bore only)" on one of the dimensions. Then dimension the other (with the desired controls) as usual.

If one does not have to be controlled differently then I would put a "2X" on the one dimension.

HTH,
Dan

Han primo incensus

 

[TheTick]

I would actually use two separate dimensions on this one. The problem I see coming is that the martinets in the inspection department are going to insist on differentiating the two separate measurements they will need to take, and they always make their documentation issues into design engineerng's problem.

 

[KENAT]

Hmm, I'm dubious on the use of fractions if you're invoking ASME stds.

2X would work for me, or separately specifying the bore depth with it's size callout.

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[pmarc]

AaronRodgers,
Out of curiosity - is there going to be any GD&T applied to this part?

 

[AaronRodgers]

Why, am I in the wrong forum? The company I work for follows its own drawing practices, including the use of fractions, which we usually list in the tolerance block as ±1/64. We make the parts here, and that is how we like to do things. That's not to say I don't ever borrow things from Y14.5. In necessary instances, we will call out things like eccentricity, face runout, parallelism, straightness, etc. I appreciate all the responses to the question that I asked, though the answer seems to be a matter of preference. I also work in the QC dept (multiple hats), and I would understand the intent regardless of which way it was dimensioned. I just wanted some other insight.

 

[drawoh]

... I also work in the QC dept (multiple hats), and I would understand the intent regardless of which way it was dimensioned.

I perfectly understand all the stuff that I do. The critical question is does everyone else understand what I am doing?

Good drafting is like good writing. You make things clear. A separate dimension on each feature is absolutely clear. A 2X on the dimension of the first feature that appears to be lined up on the first one is pretty clear. Make sure the two features are forced to line up on your CAD model.

A single dimension on one of the two aligned features can be interpreted as per ASME[&nbsp;]Y14.5, but you are pushing your luck.

JHG

 

[KENAT]

You aren't in the wrong forum Aaron, but if you don't at least nominally work to an approved standard it's difficult to give very definitive advice.

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[AaronRodgers]

That's why I'm getting advice from all you helpful folks. Off the topic a little, I have found a handful of ASME standards (some of the Ag/conveyor style sprocket standards) with several errors which left me flabbergasted as to how it can sneak by so many years without being corrected. However, that should be discussed in a different thread.

 

[CheckerHater]

Dear Aaron,
Standards are merely rules of the game, but when you ask to help with your game, while you are not playing by the rules, it may create slight misunderstanding.

 

[pmarc]

Aaron,
Be careful, you just stepped into the realm where most of people worship the only true faith called Unambiguity. Whenever CheckerHater calls somebody "Dear...", you may be sure that the person is walking on thin ice and that the cardinal sin is being committed .

 

[fsincox]

I know this will not be popular:
we used "(2)" for this situation and "2X" for the conditions shown in the standard. I know some may see this as splitting fine hairs. In my opinion, reference is just that, whatever you need it for. "2X" is specifically defined by the standard as and when and how to use it. Plus it was what we did, forever.
Frank