huangyhg

datums in multiple views
i have a drawing where it would be convenient to show 1 datum in multiple views. this is because i have to dimension off that datum in multiple views. what is the practice for this? is the datum shown in one view and then labeled reference in the other views? is the datum just shown "normal" in each view i dimension from it?
thanks,
anthony
check out our whitepaper library.
i have always shown it "normal". it would not be reference because you are dimensioning from it.
believe it if you need it or leave it if you dare.fff"> - robert hunter
per asme y14.5m-1994 3.3.2 "where the same datum feature symbol is repeated to identify the same feature in other locations of a drawing, it need not be identified as reference."
as i understand it, the datum (so long as applied to the same face/feature) can be shown in as many relevant views as you like.
it's not like double dimensioning.
in fact i've had checkers encourage me to show it more than once when it makes the drawing clearer.
kenat, probably the least qualified checker you'll ever meet...
just realized all 3 posts are from you avc8130. do you have a copy of 14.5?
it's worth spending some time looking at it as the more familiar you get with it, the easier it is to find what you need. don't get me wrong, i still sometimes can't find stuff & have to ask but i usually try and look before i ask. if nothing else i sometimes see other things that i re
honestly, i have a copy. there are actually 3 of us looking at the same copy! two of us are young engineers new to this and the other is a 30 year veteran who is well set in his ways.
i have only asked the questions that we could not find concrete answers to. "equally spaced" wasn't referenced anywhere so i didn't know if it was still allowed.
we couldn't find the answer to this no matter how much we searched. the old-timer was convinced it had to be shown as ref.
the unilateral tolerance only shows that the amount of decimals should be the same as the amount shown in the nominal. the assumption must be made that the nil value must be shown. we have 1000's of military drawings that show .500+.005.
thanks,
anthony
i didn't mean to say you were being lazy or anything, just trying to help you out. i rarely (never?) just sit down and read it but, if while looking for one thing i see something else of interest i'll maybe read it and make a mental note for when it comes up.
"the assumption must be made that the nil value must be shown" no i dont' think so, 2.3.2 (which i typed in the other thread) seems quite clear on this to me. 'its dimension shall be expressed' hence the 0 to however many dp should be shown.
kenat, probably the least qualified checker you'll ever meet...
show the datums where needed, no ref. only same dims that are shown more than once should be ref.
chris
solidworks/pdmworks 08 2.0
autocad 06
anthony,
you are asking good, valid questions.
i've been doing this sort of work for almost 30 years, and often have a hard time justifying why i do things a certain way. eq sp is an example. i've always used it, but could not point to a standard where is is specified. i can usually find documentation to back me up, but not always. as you have noted, "old-timers" tend to be set in their ways. just because i've always done something a certain way doesn't make that way valid, and i try to be open to differing opinions. if that differing opinion can't be backed up with documentation however, i generally stick to my guns.
keep on asking questions. keep us on our toes.
believe it if you need it or leave it if you dare.fff"> - robert hunter
amen, ewh. after all, engineering is a constant task to keep up with change and improvement. both young and old engineering people teach each other when both are amenable to change.
argh. yeah, you are right, ewh, and i too will start putting basic angle callouts on my hole patterns. unless i can figure out how to make inventor draw a box around the text "eq. spc."....
btrueblood,
you may not have to change afterall. i think that the concensus is that eq sp is a valid callout. see

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