huangyhg

assembly drawings - arrow tip for part callout on the outlin
hello,
the arrow tip for a part callout on an assembly drawing should be coincident with the outline of the part, correct? this is recommended over the arrow tip pointing to the surface of a part, correct? reference attached example of both methods. is this specified in the asni y14.5m standard, if so where?
i couldn't find anything myself. but common since what say arrow should point to the part, that least i would do it. interesting to see what other say.
solid edge v20
this wouldn't be in 14.5 as it's not dimensioning as such. i can't recall if 14.24 says much.
if putting a leader to a surface rather than outline our cad defaults to a 'dot' instead of arrow and i've seen this elsewhere, not sure it's in an industry standard and i don't have any of them to hand.
coverage of assy drawings really is pretty sparse in the asme stds. 14.24 covers them and there's another which covers parts lists as i recall but i can't think of the number. even 14.100 has a few relevant things. however, there really isn't that much on assy drawings all things considered.
kenat,
in all my areas of cad work (electrical, civil, architectural) i have always used, and seen, a dot for a leader to a surface, as kenat said. a dot will read "surface" and the arrow would read "this point on the surface", but i don't know if this in a standard anywhere.
see asme y14.5m 1.7.4:
"...normally a leader terminates in an arrowhead. however, where it is intended for a leader to refer to a surface by ending within the outline of that surface, the leader should terminate in a dot...
marcelino vigil
gdtp t-0377
cswp
well what do you know, i was wrong about it not being in 14.5. sorry. while it's probably not explicitly talking about balloons i'd be happy to read it across.
kenat,
yes, i am aware that when referring to a surface that the leader should terminate with a dot.
i think that this thread is getting off track. what i am trying to determine is what standard specifies that the tip of the arrowhead should touch the outline of the part in an "assembly" drawing? perhaps there is no standard for this?

that seems to answer it. an arrowhead terminating in "space" is too ambiguous - was an item removed but the balloon left behind?. termination with a dot removes that ambiguity, denoting the surface of an item as the termination.
good luck finding that in the standards though.
good to know you got shoes to wear when you find the floor."fff"> - robert hunter

thanks for all of the responses thus far. i guess my question gets more complicated with the introduction of hidden lines being used in an assembly drawing. which i believe is allowed in the asni standard.
for instance, you have two parts which overlap in an assembly drawing. lets say, a fan cover and a fan. the fan is drawn with hidden lines, while the cover is drawn with solid lines. if you were to use a leader that terminates with a dot(indicating surface) and that dot is coincident the fan and the fan cover, which part would you be referring to?
i would suspect the fan cover, but i could be wrong. if a leader arrow terminated on the outline of the fan cover and a leader arrow terminated on the hidden outline of the fan, there would be no ambiguity, as i see it.
so, my preference would be to use a leader with an arrow that terminates on the outline of the part, rather than using a leader with a dot that terminates somewhere on the part surface. however, i cannot find a standard to back up this claim. if anyone can find it, i would be interested in learning about it.



you shouldn't be terminating to hidden lines. i would create a break-out on the cover to show a portion of the blade, then use an arrow termination on both cover and blade. if you didn't want to go through that trouble, and if it is not ambiguous, i would use a stacked balloon and only point to the cover. people will see the part list and be able to determine what they need.
"art without engineering is dreaming; engineering without art is calculating."
i agree with mm. as in dimensioning, you should not point to hidden objects, but create a breakout. if there is no breakout, then the cover would be the item referenced.
good to know you got shoes to wear when you find the floor."fff"> - robert hunter

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