"Equally Spaced" 3

[avc8130]

I am currently reviewing drawings drawn to 14.5-1973. I am finding the "Equally Spaced" used quite often to call out holes around a Basic circle. We are having a discussion over how the positional tolerance applies. Does the "Equally Spaced" get treated as a Basic callout and the positional tolerance apply on the circle after the equally spaced math is done? Or does the tolerance in the title block apply to the "Equally Spaced" and then the positional tolerance only applies to the holes location on the pattern circle?
Thanks,
Anthony

 

[MintJulep]

You have probably already given it more thought than the designer of drafter did when making the drawing.

I would treat treat is as a basic dim and apply the positional tolerance from there.

 

[ewh]

I agree. If the feature is otherwise located using basic dimensions, it is safe to infer that the angular dimensions are also basic.

Believe it if you need it or leave it if you dare. - [small]Robert Hunter[/small]

 

[avc8130]

Is "equally spaced" a valid callout within ASME 14.5?
Thanks,
Anthony

 

[ewh]

I don't recall 14.5 addressing this issue.

Believe it if you need it or leave it if you dare. - [small]Robert Hunter[/small]

 

[KENAT]

I'd treat the equally spaced as basic.

A possible way to figure it out, does the positional FCF show a diameter symbol for the tolerance zone? If so I think the equally spaced would have to be basic for the tolerance to make sense.

However, I don't have a copy of, or familiarity with the 1973 version (I wasn't born yet). There are a couple of regular posters here who probably did work to it, they may know.

I don't believe the current version, ASME Y14.5M-1994 addresses "equally spaced" (or equispaced as we used to say in the UK). The examples appear to show 6X 60° (basic) or equivalent. I don't see it listed in appendix C either.



KENAT, probably the least qualified checker you'll ever meet...

 

[ctopher]

Everyone aboce is correct.
Here in the USA it is OK to call out equally spaced, except use "EQ SP". I have not seen anything that says you can't use it.

Chris
SolidWorks/PDMWorks 08 2.0
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog

 

[avc8130]

The FCF shows a .004 diameter tolerance zone. The old-timer's opinion is that you would divide 360 degrees by the instances (3 holes). That would give you 120 degrees separation. Then you would apply the title block tolerance of +/- 30 minutes. After that you would get your angular location on the pattern circle (basic) and then apply the .004 diameter tolerance zone.

My opinion is that the "eually spaced" has to be basic to make sense. Using his math 119.5 would NOT be "equally spaced". He then argued after applying the .004 diameter tolerance zone that they wouldn't be equally spaced. I told him he was taking on the whole definition of BASIC with that statement!

 

[KENAT]

Actually, in ASME Y14.38-1999, Abbreviations & Acronyms, the abbreviation for EQUALLY SPACED is EQLSP, if you care.

KENAT, probably the least qualified checker you'll ever meet...

 

[ctopher]

Works for me.

Chris
SolidWorks/PDMWorks 08 2.0
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog

 

[KENAT]

I think the old timer is wrong but...

I'm young & inexperienced so can you be sure I'm right;-).

KENAT, probably the least qualified checker you'll ever meet...

 

[WHITMIREGT]

I went to the 1973 standard, and it states for repetitive dimensions where a pattern of holes has EQL SP without a FCF "Any such method of dimensioning should include the appropriate specification of applicable tolerance." If the pattern of EQL SP has a FCF, "Basic dimensions establish the true position from specified datum features and between interrelated features."

 

[KENAT]

Thanks Gary (star for you), so from my understanding of your post I'd say avc8130 and the rest of us were correct, the other guy is wrong.

Now for a post over on "How to Improve Myself to Get Ahead in My Work" or "Overcoming Obstacles Getting My Work Done" on how to break this to your more experienced co-worker;-).

KENAT, probably the least qualified checker you'll ever meet...

 

[CheckerRon]

Well, this question had me trying to access a long unaccessed mental database and digging into my moldy old yellowed 1973 addition too. Although my instant thought was "yes it does mean basic angles.

WhitmireGT, the expert, nailed it and stopped my search.

As to "Is equally spaced a valid callout in ASME Y14.5?" No, but it was in ANSI Y14.5-1973.

 

[ringman]

avc8130

I thinketh the old timer has a basic misunderstanding. To my knowledge, it has NEVER been permissible to mix basic and +/- dimensions in a callout.

 

[CheckerRon]

You're right ringman. I think that old timer either doesn't remember, or never knew in the first place.

Back in the 1966, 1973 Y14.5 days there was a lot of mixing of basic and ± dimensions, and it was a disaster when trying to do tolerance stacks to check assemblies, especially with already released (and often built) parts.
I worked a lot of MRB then and verifying the acceptability of discrepant parts made to such drawings was an education in tolerancing.

 

[ctopher]

I just wanted to be #16 to make this thread equally spaced.

Chris
SolidWorks/PDMWorks 08 2.0
AutoCAD 06/08
ctopher's home (updated 10-07-07)

 

[WHITMIREGT]

If you are talking about me, I agree with ringman. The two definitions I copied from the 73 standard was two different dimensioning subjects. The one subject is when no FCF is used, EQL SP must have a ± tolerance associated with the dimensioning. The second subject is when there is a FCF, then the dimensions are basic with no ± associated tolerance.

 

[btrueblood]

ewh replied elsewhere in this forum to something I said...

It sounds as if some of y'all will keep using EQ SPC on drawings per Y14.5-1994. I got a different read on this subject after looking thru all the posts. In my mind the confusion is avoided by specifically calling out the pattern with a basic dimension (e.g. "8X 30 deg."), and since the latest Y14.5 does not specifically deal with "EQ SPC", it should be avoided on new drawings. I agree with the interpretation that EQ SPC should be considered a basic dimension for position-controlled features, but if the argument could be avoided by being specific, I'll opt to avoid it.

 

[btrueblood]

Or am I being too specific?