huangyhg

how many angles are in a circular pattern?
see attached drawing.
is fig. a or b correct?
let me ask you the question...which one do you think is correct, and why/why not?
chris
solidworks/pdmworks 08 3.1
autocad 06/08
i think that the asme standard declares figure a "the method" but... good question!
why reiterate the obvious?
paul
it is 5 x 72 degrees.
dave d.
it is 4 x 72 or you are dual dimensioning, implicitly on the tolerance.
unless of course you are using basic & positional in which case 5x is correct, and which would be better.
it's amazing how angular tolerances tend to add up, especially as the radius increases.
if you have 5x 72 +-.5 then on the last 'segment' it's actually possible that you are speccing both 72+-.5 or 72+-2. as such not only are you dual dimensioning but the dual dimensions conflict.
of course if you use 4x and dont give which direction then which segment is 72+-2 is open to variance.
just use basic and positional if you care about the final location.
kenat, probably the least qualified checker you'll ever meet...
english or metric? :>) neither as shown since they are not associated with the center.
if basic were used it would provide for the association allowing that the proper datum features were specified and related.
imagine that the pattern is actually being machined on a good old fashioned bridgeport with a rotary table attached.
how many times does the machinist need to change the angular position?
check page 49 and fig 1-56 in y14.5-1994. you always count the spaces. 5x 72°
cwdaniel,
you might also look at fig 4-15, 4-16 and 4-17 of y14.5 -1994. if you are using geo tolerancing, i think either method will work. if you are not using geo tolerancing, as shown in the attached drawing, both would be incorrect in that they do not locate the apex of the angle.
in answer to your original question, i believe you can have as many angles as you would like in a circle.
very good question! i've often had this philosophical discussion, and i am in complete agreement with kenat. 4x or 5x 72 if using basic dimensions (both return same result), 4x if using +/- tolerancing due to the tolerancing build up.
i have to caution anyone from following the illustrations in the standard for anything other than what they are trying to explain. page 49 fig. 1-56 is intended to show feature control frame placement, and the angular dimension is not addressed in the text. on page 1, para 1.1.4 it is stated that "the figures in this standard are intended only as illustrations to aid the user in understanding the principles and methods of dimensioning and toleranceing described in the text."
i've heard arguments either way, but that's my opinion, and i'm sticking to it (until shown otherwise).

believe it if you need it or leave it if you dare.fff"> - robert hunter

i knew this might be a bit contentious. it always has been in my past.
ctopher: i'm asking the question, not providing my forgone conclusion. i can be swayed by the argument of folks with qualified opinions. in fact i've flip flopped on this several times. mostly due to the all powerful reign of the checker i'm working with at the time.
pauljackson: can you find that specific asme standard declaration? i'd love to be able to refer to something in writing.

currently i'm on the side of "b". however, kenat i haven't heard the argument of it depends on whether gd&t is involved or not. yet another wrench in the monkey works. i'll have to ponder that one.
mintjulep: i think your analogy is what makes sense to me. there is always one less space than there are features in a pattern. and we are dimensioning spaces. yet our standard makers seem to be conflicted in their examples fig 1-55 is showing us 5 spaces in a 6 hole pattern while fig 1-56 shows us 8 spaces in an 8 hole pattern. fig 1-56 further confuses me as the space to the 1st hole is shown and not as a reference.
ringman: your comments about location of angle apexes and centers seem to miss the topic. my examples were submitted to address a specific question, not as drawings with complete requirements. if you're suggesting that the apex isn't defined because the center lines do not cross, then ok. maybe that's another topic. at the risk of further derailment, your reference to figs 4-15, 4-16 and 4-17 don't extend the center lines either.
ewh: thanks for the reminder of the caveat about the illustrations.
so, does the amount of spaces in any given pattern change whether it's circular, radial or linear? i've never given the dimension of the space back to the 1st hole of a linear pattern, why would i do it on a circular one? would you dimension the leftover space in the radial pattern shown in fig 1-55?
i'm usually bowing to the wisdom (or lack thereof) of the checkers and conventions of the employer i work for. i'm now in a small company and finding myself as the checker and referee in things of this nature.

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