this is incorrect. The OPs attachment clearly shows B & C as centerplane datums per ASME Y14.5 when the datum symbol is placed in line with the feature of size it is a centerplane datum. See ASME Y14.5-2009 fig 3-4.
the result of the OPs drawing is a 0.1 profile of all 4 sides.
lightweight...
they are correct. The profile zone encompasses all 4 sides. Datums B & C are shown as centerplane datums and are not the edges of the part, I agree they are not needed.
lightweight, cheap, strong... pick 2
A center plane can most certainly be a datumn and in many cases is certainly practical. (I cant see enough detail in your picture attachment to really comment but it almost looks like what appears to be Datum D is placed like its a centerplane datum... be careful where you place your datum...
If the cover is supposed to sit over the housing, then it needs to be centered on it... the centerplane would be a better way to locate from. I agree you have it backwards because you should want to build your gauge to the MMB of the housing, not the cover itself.
lightweight, cheap, strong...
Greenimi, My apologies if I came across sarcastic, wasn’t my intention. But I did answer gabimot’s question as how I read the drawing. I have a copy of Y14.5-2009 but not Y14.2… which IIRC covers the use of lines like centerlines, maybe I missed it but I couldn’t find anything in 14.5. So you...
Checkerhater, I had to think about this one for a minute but your right, the only thing that establishes a pattern is a geometric tolerance.
So without the use of a geometric tolerance, the centerline only means the .500 dimension applies to all 4 features independently, the same thing as “4X...
What does the centerline mean when used to show a pattern of features?
Does it mean only to indicate all the features individually within the pattern or does/can it mean an average location of the features in aggregate?
Attached is a drawing example for this question... to me, both examples...
if you know what method works best for you, you can specify the exact manufacturing method on the finish symbol or drawing notes. e.g.: 32µin grind, you can be as specific as you want in the drawing notes.
lightweight, cheap, strong... pick 2
centerlines can be used to indicate different things; a centerplane, a linear or other pattern of holes, a hole or cylinder axis in a side view... and as far as I know they are optional to use, usually added in an attempt for clarity. Personally in this case I think the centerline is also...
Apex,
sometimes I cant figure it out its frustrating, it doesnt happen all the time to me though. I know if you've rotated the view in the drawing it messes up alignment, like with using ordinate dimensions. Also try selecting the datum tool first, then select the dimension.... sometimes thats...
select the dimension then select the datum tool and it should attach in line and move with the dimension.
Sometimes it doesnt work for me though it attaches opposite (in this case that would be vertically) and I've had to manually place it in-line thus having to move both to re-adjust location...
yes, correct you dont need the .375 basic dimension.
Apex..., see attached example for correct placement of the datum A symbol. For it to represent the centerplane of the width of the part it must be placed in line with the dimension otherwise it only represents the surface.
As far as...
ApexMOEng,
Reccomennd to use position instead of symmetry... the difference is symmetry is a relationship of centerplanes where what your really wanting to do here is position the holes about the center of the part, so use position.
Put the datum A attached (inline) with the .750 width...
Happystamps,
The correct callout in your original attachment is Datum C witch properly establishes the datum axis.
ASME Y14.5-2009 Fig 3-4 (pg 38-40)shows the correct placement of datum feature symbols. It doesn't explicitly state that it cant be placed on the surface or leader line but in all...
I get poorly done drawings from customers all the time. Datums to centerlines are common even today. Challenging the customers drafting ability isnt an option, making the part they want is an opportunity to make money. Call them up and ask them which hole Datum D is defined from and get the...
not upset or angry on my part, just dissapointed. Like I said in my OP I have no problem if that's what they really want to do its their business.
lightweight, cheap, strong... pick 2
Datum D is shown from the C/L of the orthographic view derived from the right side view showing the Ø.250 hole. So the Ø.375 hole is called out to be concentric to the Ø.250 hole axis which is Datum D.
If the drawing was done in 1989 the standard might be ANSI Y14.5M 1982.... I think...
If the MODs want to close or delete this thread I understand since its not a direct discussion of GD&T etc.
What I’m posting this for is to ask the community to consider sending tec-ease.com a polite email asking them to reverse their new policy requiring premium membership. Personally, I have...
my default is to use the biggest tolerance the design allows even if the process is capable of a fraction of that.
lightweight, cheap, strong... pick 2
