【转帖】equally spaced

yang686526

"equally spaced"
i am currently reviewing drawings drawn to 14.5-1973.  i am finding the "equally spaced" used quite often to call out holes around a basic circle.  we are having a discussion over how the positional tolerance applies.  does the "equally spaced" get treated as a basic callout and the positional tolerance apply on the circle after the equally spaced math is done?  or does the tolerance in the title block apply to the "equally spaced" and then the positional tolerance only applies to the holes location on the pattern circle?
thanks,
anthony
eng-tips forums is member supported.
you have probably already given it more thought than the designer of drafter did when making the drawing.
i would treat treat is as a basic dim and apply the positional tolerance from there.
i agree.  if the feature is otherwise located using basic dimensions, it is safe to infer that the angular dimensions are also basic.
believe it if you need it or leave it if you dare.fff"> - robert hunter
is "equally spaced" a valid callout within asme 14.5?
thanks,
anthony
i don't recall 14.5 addressing this issue.
believe it if you need it or leave it if you dare.fff"> - robert hunter
i'd treat the equally spaced as basic.
a possible way to figure it out, does the positional fcf show a diameter symbol for the tolerance zone?  if so i think the equally spaced would have to be basic for the tolerance to make sense.
however, i don't have a copy of, or familiarity with the 1973 version (i wasn't born yet).  there are a couple of regular posters here who probably did work to it, they may know.
i don't believe the current version, asme y14.5m-1994 addresses "equally spaced" (or equispaced as we used to say in the uk).  the examples appear to show 6x 60° (basic) or equivalent.  i don't see it listed in appendix c either.
kenat, probably the least qualified checker you'll ever meet...
everyone aboce is correct.
here in the usa it is ok to call out equally spaced, except use "eq sp". i have not seen anything that says you can't use it.
chris
solidworks/pdmworks 08 2.0
autocad 06
the fcf shows a .004 diameter tolerance zone.  the old-timer's opinion is that you would divide 360 degrees by the instances (3 holes).  that would give you 120 degrees separation.  then you would apply the title block tolerance of +/- 30 minutes.  after that you would get your angular location on the pattern circle (basic) and then apply the .004 diameter tolerance zone.  
my opinion is that the "eually spaced" has to be basic to make sense.  using his math 119.5 would not be "equally spaced".  he then argued after applying the .004 diameter tolerance zone that they wouldn't be equally spaced.  i told him he was taking on the whole  definition of basic with that statement!
actually, in asme y14.38-1999, abbreviations & acronyms, the abbreviation for equally spaced is eqlsp, if you care.
kenat, probably the least qualified checker you'll ever meet...
works for me. ;)
chris
solidworks/pdmworks 08 2.0
autocad 06
i think the old timer is wrong but...
i'm young & inexperienced so can you be sure i'm right.
kenat, probably the least qualified checker you'll ever meet...