what is best way to control location of coaxial hole

[bxbzq]

On drawing I need to drill a multi-stepped hole on a thick wall. There are say 6 coaxial diameters on the hole. What is the best callout to control the location of the diameters with positional tolerance control?

1. Use positional tolerance control for each diameter with same datum features reference. I think this would make the drawing kind of verbose. Is there a better way?

2. I see drawings drafted by my colleague show a single positional tolerance control applied to the axis of the hole. I guess the control of this callout is equal to the first one. But I'm not sure if it is an appropriate way because it just reminds me of the datum symbol placed on an axis.

3. Use a composite position tolerance control with a notation like 6 COAXIAL DIMATERS. This is a nice one but there are fewer people understand exactly what it means. Besides, the design intent, I guess, is not to control the coaxiality of the diameters. It just wants to control the location of each diameter individually.

Thank you for inputs.

 

[bxbzq]

I mean, forget the interrupt.

 

[pmarc]

bxbzq,
Your last try is for sure illegal per ISO 1101:2004. ASME Y14.5 does not specifically say it is forbidden, but offers no example of such approach and does not mention it when listing which methods are allowed (para. 3.5 of '94 and '09 editions).

 

[bxbzq]

pmarc,
OK. This is not bad news for me. It shows how my colleague does. Thank you for pointing out.

 

[CheckerHater]

bxbzq,

As you mentioned cylinder, you reminded me my dealings with hydraulics long ago; and I can assure you: the drawings for cavities like in your example can be quite "verbose".
The one on the link is not the most complicated.
So use as many direct and geometrical tolerances as you need to fit mating part properly.

 

[fsincox]

"I think we will all agree on the "best way", safe?"

Looks like I was wrong about that too!

Ken,
I agree your way can be done; I was caught up in terminology of “the best”. I think of best as my interpretation of the ASME’s intent: "best describes function" he may mean “best” as in easiest. I also agree that if he calculated a c’bore like you showed in the M42 c’bore thread it could be both.

bxbzq & CH,
I suspect the more steps in a bore, like is shown here, the less likely a single tolerance will be the “best“ from the functional point of view and more of just a compromise. If you just want compromise, this is why I was also heading down the general tolerance path as an option.
Frank

 

[bxbzq]

Frank,
I should not have used "the best" in the title. Probably "appropriate" would be fine.
I agree your point of function. If I were the designer, I would use composite positional callout to tune the control. Then education to supplier and inspector may be needed.

 

[fsincox]

Your words are fine, comunication is an art, that unfortunately, I am short on. I needed time to understand what you are asking for, I start with my own predisposition of the words and then need to try and understand what you are actually trying to say.
Frank

 

[bxbzq]

Frank, you probably can tell English is not my native language...Even though, it should not be an excuse. I'll try to write my post with precise wording.

 

[KENAT]

Like pmarc says, the way you've tried to do it (point the FCF to the CL) is wrong. The way 14.5-94 shows it in 5-37 is correct - that is the FCF is attached to the hole dimension call out.

As for multiple (more than 2) coaxial bores, this is covered in 1.8.11, especially figure 1-37.

Like I said from a drawing annotation point of view it's perfectly reasonable. However, you'll have to determine if functionally it's appropriate.

Please note that I keep referencing the standard I'm referring too - if you're using ISO or something it may be different.

Posting guidelines faq731-376

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

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[fsincox]

bxbzq,
This is just as true of two people who speak "the same language". It is not just you.
Frank

 

[MintJulep]

The easiest way is to use a Relativistic Klystron Oscillator.

thread1103-317598

 

[vigildesign]

I would look at Fig 5-53 in Y14.5M, so option #3.

 

[fsincox]

CH,
I used to work in hydraulics too.
Do you think your linked example really best represents the ASME's or ISO’s intent with just those few callouts shown?
I am curious if anyone else wants to chime in, too. I have no doubt it is common, that is not the question, I mean the ideal intent of the committee’s stated intent that all features should have definition and specify the functional requirements?

I know I do not, I am certainly an idealist though.
Frank

 

[CheckerHater]

Do you think your linked example really best represents the ASME's or ISO's intent...

No, it's just first relevant picture I found "on the Internets".

My point being - you can have dozen features, some embracing the mating part, some just providing clearance; you can have several criteria from "simple" fit to dealing with sharp edges that can damage rubber seals, etc., etc.

You will not get the good part unless you explicitly specify all your requirements. So looking for "call-out" that will save you some space on the drawing is just plain dangerous direction to go.

 

[fsincox]

"and the congregation says: AMEN"
Frank

 

[PaulJackson]

This example is typical of hydraulic spool bores and injector bore sets. It eliminates having to designate datum features when there are numerous bore cross-sections and it prevents simultaneous requirement linking of the refined bore pattern position requirements.
Paul

 

[fsincox]

Paul,
Cylindrical zones on surfaces?

If you are not going to specifically tolerance all the bores to their functional limits, to me what you did there is not much different than just placing a straightness on the axis like the old ISO practice.
Frank