Location of a hole pattern

[wojciechr]

I have a pattern of 4 holes, which in turn exists in 4 places of a frame. Engineer wants to give it a location tolerance of 4mm in X axis, 2mm in Y axis, and wants to tie each of the 4 holes to each other with a tolerance of 0.6mm. I came up with top option, which in my opinion is better, but checking prefers bottom option. Do you see anything wrong with either of those options? Would you consider different method all together?

We're using latest ansi standard.

Thanks,
Wojciech

 

[KENAT]

What standard are you working to? My response is based on ASMe Y14.5M-1994.

The top one is not clear on the bidirectionality and is definitely wrong from my understanding.

The bottom one is a bit better but I'm still not sure it properly captures the fact that it's a composite tolerance.

I'm not sure if there's a completely proper way of doing what you want shown or explained in the standard. I'd be tempted to move the .06 FCF over to the bidirectional call-outs and set them up as more conventional composite FCF with FRTZF & PLTZF.

Also in both I think you have the order of the C'bore and thread reversed, see fig 1-37 of ASME Y14.5M-1994

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[wojciechr]

Yes, we're using asme standard.

Datum A-B is horizontal (2mm tolerance), E is vertical (4mm tolerance). Isn't that enough to give it the directionality in top view?

 

[ewh]

I'm not sure of KENATs objections, but I find the first one more concise, and (assuming the datums are clearly defined) would have no problem interpreting it.
In the second example, you have to assume that the separate controls actually apply to all of the holes.
I could easily be missing something, though.;-)

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[wojciechr]

ewh,

Is the "4X INDIVIDUALLY" note clear to you too? We have not used that note before (you could say we're still transitioning from gm standards), but I found it in the asme book some time ago and I think it applies here.

Before we would create detail view of one of the hole patterns, and say it's a typical view so many times.

Because it's something new, we have some hesitation about it... And... I really don't like fragmenting my drawings with multiple detail views... I think it makes the drawing harder to read...

 

[KENAT]

Bidirectional tolerancing itself is addressed in the standard at section 5.9 figure 5-41.

However, it is not extrapolated to composite tolerancing.

Essentially the OP wants a diametrical tol zone for the FRTZF and ectangular Bidirectional for the PLTZF.

I'm not 100% sure of the correct way to do this but the top option doesn't look anything like figure 5-41 and doesn't comply with 5.9.1 as I understand it.

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[ewh]

Yes, upon reflection the composite is confusing.
If the relationship between patterns is not important, I think I would combine the two examples, using the first's callout structure (replacing "16X" with "4X") and placing it in a detail view which could be labeled as the example (TYP 4 PLCS). That eliminates the confusion regarding "4X INDIVIDUALLY" (at least to me).

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[wojciechr]

Kenat, ewh,

I modified the view, going by 5.9.1 section of gd&t and section on Repetitive patterns on

http://www.tec-ease.com/tips/march-01.htm

UUsing appropriate datums for H and V instead of V/H arrows seems clearer to me, but I guess standard is standard and it will have to do...

 

[MechNorth]

The single feature control frame "composite" offered in the original posting was wrong. There is no directionality for the rectangular zones, so it's just wrong. The second layout in the same post was valid, but would have linked all 4 holes in each of the 4 patterns together.

If this is a pattern of hinges or such where you want the four patterns to be linked to each other globally, but the four holes within each pattern to be related only within that one pattern, then the use of "individually" as provided on the latest post is correct. If, however, you want each of the 4 groups of 4 holes to be independent of each other, then you would need "individually" under each of the H/V positional feature control frames as well.



Jim Sykes, P.Eng, GDTP-S
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[wojciechr]

Just wrong, gotcha

Thanks!