Datum use with a pattern of a pattern?

[ligo]

See My attached jpg.

Does this Datum/Pattern say what I want it to say?


What I want it to say is:

Give me a pattern of large circles located within .02 of Datums A,B,C. And around each large circle, 4 small circles within .005 of their basic location relative to each large circle the 4 are around.

Thanks for you help.

 

[PeterStock]

Basicly yes, but I would still suggest that those on the B datum side use the B datum.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

http://www.infotechpr.net

http://www.linkedin.com/profile/view?id=30064526&trk=tab_pro

 

[dtmbiz]

Ligo,

It appears that you are improving the drawing. I agree with pmarc that you should consider clocking the hole patterns around the large holes. Currently the callout will not control rotation of the pattern around each large hole; unless you aren’t concerned if the 4 hole patterns could for example be at 45 deg to one another.

Datum C in the lower view is not the surface you are dimensioning from in the top view. Basic dims need to originate from a datum. In this case the dims are inverted. The 0 and 5 should be swapped as far as the current datum C surface. The other dims need adjusted as well, originating from datum C.

I also believe that in baseline dimensioning that there can be only “one” zero. In detail K this is confusing to have another “zero”. The callout for the patterns reference’s datum E and implies that those dimensions are from datum E, 12 individual places. That would be the 2 center planes intersecting the axis of datum E. IMO that is good enough without putting a zero at the center of the large hole datum E.

I certainly would remove datum B from the drawing unless it is or will be referenced somewhere that is not shown.

 

[dtmbiz]

Ligo,

If the drawing is 1st angle projection then your dimensions in the top view are correct. My bad for "assuming" it is a 3rd angle projection.

 

[ligo]

dtmbiz, As stated earlier in the discussion, clocking of the 2-56 holes in not relevant to the parts function.

I'm not clear on what you mean by dimensions from Datum-C not being consistent between he top and bottom.

Do you have a reference for Ordinate dimensioning not being able to have a second zero in a detail view? That is one of my concerns and I'd like to lock it down.

Thanks

 

[dtmbiz]

Ligo,

The bottom horizontal line in the bottom view representing datum C is the most upper horizontal line in the top view. The line which has dimension 5 should be 0, since basic dimensions originate from a datum. The drawing currently shows datum c in the bottom view and is dimensioned from the oppostite end of the part in the top view. This is basic orthogonal projection for 3rd angle projected dwgs.
I am presuming this part is dimensioned with 3rd angle rotations. 1st angle projection would be another story.

Baseline dimensioning should have one zero for x, one for y, and if necessary one for zero at one common origin. This is per the part, not per each view. If you took away detail K and put the zero for the large hole in the upper view where detail K originates from; then you can see how confusing this is.
You would have zero at the left edge of the part and zero at the center of the large hole.

 

[ligo]

Ok, I got ya now. I thought you were referring to "just the views" without any dimensions or datums. And I agree, now that I see what you are saying.

I tend to agree with your logic on baseline dimensioning methodology, I but I'm not seeing anything in Y14.5 to say so.