How many angles are in a circular pattern?
How many angles are in a circular pattern?
(OP)
See attached drawing.
Is fig. A or B correct?
Is fig. A or B correct?
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How many angles are in a circular pattern?
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How many angles are in a circular pattern?How many angles are in a circular pattern?(OP)
See attached drawing.
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RE: How many angles are in a circular pattern?
Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Apr 30, 2008)
RE: How many angles are in a circular pattern?
Why reiterate the obvious?
Paul
RE: How many angles are in a circular pattern?
Dave D.
www.qmsi.ca
RE: How many angles are in a circular pattern?
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...
RE: How many angles are in a circular pattern?
If basic were used it would provide for the association allowing that the proper datum features were specified and related.
RE: How many angles are in a circular pattern?
How many times does the machinist need to change the angular position?
RE: How many angles are in a circular pattern?
RE: How many angles are in a circular pattern?
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.
RE: How many angles are in a circular pattern?
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. - Robert Hunter
RE: How many angles are in a circular pattern?
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.
RE: How many angles are in a circular pattern?
The 5×72° callout makes perfect sense to me. It shows that the holes are equally spaced on the pitch circle. If I went 4×70°, it is fairly clear that the spacing is not equal.
JHG
RE: How many angles are in a circular pattern?
It boils down to semantics, and I feel that both sides have merit. I eagerly await a definitive answer to this problem.
Until then, I suggest doing whatever the checker wants ;)
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
I don't know if you looked for answers at your work place or if you are a student. I was simply asking your thoughts what you think the answer should be. I didn't want to just give you an answer and send you off on your way without response from you, I didn't know.
Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Apr 30, 2008)
RE: How many angles are in a circular pattern?
And again without GD and T the examples you gave are 'ambiguous'.
RE: How many angles are in a circular pattern?
Paragraph 1.9.5.2 of ASME 14.5M-1994 explains spacing...with and without the use of the "X" symbol. It refers to illustrations that are consistent in declaring the # of spaces between features... as are other illustrations throughout the standard...
So one may conclude from that that the 5X 72° trumphs 4X 72° however fundamental rule 1.4 (c) states, "Each necessary dimension of an end product shall be shown. No more dimensions than those necessary for complete definition shall be given..."
So I still think that it was a good question but I would go with the practice that is illustrated throughout the standard just to be consistent.
Paul
RE: How many angles are in a circular pattern?
Therefore, I think that it would be produced the same regardless of which way it was dimensioned here.
However, without a standard I would interpret it as there should be 5 spaces at 72 deg. Additionally, I would think the dimensions being like basic, and the third hole should be (3*72) = 216 deg from vertical, +/- the angular tolerance. If the tolerance for all holes was +/-1 deg and the second hole was at 143 deg, I would not accept the third hole being at 214 degree, even though that is within the tolerance stack-up. However, without a standard I wouldn't really have a leg to stand on if it became a dispute anyways.
I guess I just feel that it is more likely to fit function if the basic positions of the holes are given, and the tolerance applied to those. It wouldn't make much sense to allow the tolerance to stackup in this case (I presume, without knowing the application). If the angular locations are taken as basic, I think 5X 72 makes more sense since it gives the complete circle. If the position is based on stacking up the tolerances from one hole to the next, this does over-define the last hole, but if they are taken as basic then it doesn't really matter.
-- MechEng2005
RE: How many angles are in a circular pattern?
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
Basic (for me) is the only way to go for holes, so forget ± tolerance.
There are those that would argue with me, but I have always wished that ¶ 2.1.1.1 of Y214.5M-1994 started out with "Manditorialy" rather than Preferably"--that is, Basic dimensions vs ±.
WhitmireGT sort of got picked on for citing Fig 3-25, and there was merit in the criticism, but it is still a good example. Morever, it is one of the few Y14.5 examples where the part is fully dimensioned, and that lends some credence to it.
Besides that, it agrees with way I see it
(Checker's preference sneaking in---EWH opened the door).
RE: How many angles are in a circular pattern?
My only difficulty grasping the concept is that I was taught to always avoid double dimensioning. If you have a circular hole pattern and the topmost hole is properly located and use the total no. of angular spaces, then the "extra" angular dimension is also locating that hole. All the holes are tied down without that extra angle, so what is its purpose?
Not quite string theory, but it bugs me.
I'll be good though and follow the standard.
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
Unless, could you just write the note "5 holes, equally spaced"? Oh wait, we already beat that horse to death, didn't we?
RE: How many angles are in a circular pattern?
Here are my two cents:
1. A note that says 5 holes equally spaced.
2. A dimension, as shown, if the holes are not equally spaced.
To btrueblood,
This is not land surveying but machine parts.
John H. Dunten, CD
Certified Drafter
RE: How many angles are in a circular pattern?
Usually I wouldn't say artillery-baiting stuff like that, but it's nearly the 4th over here, and we kinda like loud noises for that...
RE: How many angles are in a circular pattern?
RE: How many angles are in a circular pattern?
Made the mistake before but never again.
Kim
RE: How many angles are in a circular pattern?
RE: How many angles are in a circular pattern?
Now, along the same lines (no pun intended), have a look at another possibility I've run into. See attached dwg.
Does having the holes connected by a common center line negate the requirement of specifying the number of angles?
RE: How many angles are in a circular pattern?
Once this is detrrmined, we can come to a solution, perhaps.
RE: How many angles are in a circular pattern?
I have seen hexagon features dimensioned this way also and I think it is poor substitute for BASIC and an FCF for the features. In the case of hexagon dimensioning I think it is wrong.
RE: How many angles are in a circular pattern?
RE: How many angles are in a circular pattern?
RE: How many angles are in a circular pattern?
If you use GD&T style positional tolerances on your holes, most angle dimensioning schemes are perfectly functional. Your drawing is unambiguous, although it is not explicitly shown that your angles all are equally spaced. I might use your dimensioning scheme if my two angles were, say, 57.5°.
If you apply ± tolerances to your drawing, you need to work out the effect of your allowed error. This may be weird. The linear displacement due to your angular error is affected by the pitch circle. This all is an excellent argument for GD&T positional tolerances.
JHG
RE: How many angles are in a circular pattern?
RE: How many angles are in a circular pattern?
If you dimension as "5 x 72" then the angular tolerance applies to 5 individual dimensions. This leads to the possibility that 5 individually conforming features result in a non-conforming part. Over-constrained, ambiguous, whatever you want to call it, it's wrong.
Dimensioning as "4 x 72" eliminates the over-constraint and ambiguity - although it may not yield "conforming" parts that work.
Yes, the last hole may be "way off" from where it really needs to be. This arises from the poor decision to use chained dimensions.
Yes there are. They are: 0, 72, 144, 216, and 288 degrees. If those angles are where you want your holes, then those angles should be dimensioned. Or specify 72 as basic, and use GT&T to control the location.
RE: How many angles are in a circular pattern?
Would you draw 4 tires on a car, but show 3 on the BOM?
Fig A is the correct drawing. They are shown eq sp, but not indicated...and should be.
72 x 4 = 288
72 x 5 = 360
Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 02, 2008)
RE: How many angles are in a circular pattern?
Re 1.9.5.2 of ASME 14.5M-1994 & figure 1-56, it can't be used to fully answer this question because it doesn't address tolerance and as 1.1.4 is in force can't be readily extrapolated from the figure.
Fig 3-25 on page 49 is clearly using Basic, in this case I agree with X being the total number of spaces and = the number of holes, no tol stack up.
It's quite possible that the theoretical 'complete drawing' that 1-56 is taken from has the old "UNTOLERANCED DIMENSIONS LOCATING TRUE POSITION ARE BASIC" note somewhere we can't see or something.
I'm apparently disagreeing with several posters that are far more qualified than I, which I'm usually loathed to do but in this case, if not using basic then I can't see how 5X72 with +- tolerancing can be correct when you take tolerances into account.
As to over analyzing, no I'd say that considering the tolerance aspect is adequate analyzing. It's ignoring the tolerance aspect that is under analyzing the situation.
Given that virtually all the examples in the standard use basic/position on this type of hole pattern I disagree with the "use 5 X 72 because that's how it's always shown in the standard" argument.
5 X 72 without using basic or some other custom note/requirement leads to having two different allowable tolerances on one of the dimensions, I believe this contravenes the standard but can't quote chapter & verse. 1.4 (c) sort of addresses dual dimensioning but not explicitly. 1.7.7 is kind of relevant So if you consider that showing the holes in a circle implies 360° then you should leave one angular dim out, but it's perhaps a stretch.
It's not the explicit dimension scheme that is so much the concern as its implications on tolerance.
However if we're happy to ignore that then use whichever floats your boat.
KENAT, probably the least qualified checker you'll ever meet...
RE: How many angles are in a circular pattern?
As I have stated before, I will use 5X 72° when the dimensions are basic, per the standard - no tolerance stackup involved. I still need convincing in regard to +/- tolerancing. MintJulep makes a valid point that "the last hole may be "way off" from where it really needs to be. This arises from the poor decision to use chained dimensions".
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
It's like saying you have 5 steps on a shaft, and you chain dimension all 5 steps, and then dimension the entire length of the shaft. It's over-dimensioning. The only difference is that the "entire angular length" of the circle is implicitly 360 degrees.
V
RE: How many angles are in a circular pattern?
RE: How many angles are in a circular pattern?
Remember, you are measuring a part as it exists in it's final configuration, NOT writing an operation sheet for a machinist. The 5th dimension exists even if the machinist does not have to make the move. 4 x 72 allows accumulation where as 5 x 72 actually limits the fifth space as well. The "equals 360" is understood because of the vert/horiz divider rule in angular dimensioning. 'If you start on the vert and go all the way around 360 is apparent, no?'
Your standard tolerances control the first 4 'moves' and the vertical start line is also the end which can't move so the dimension from the 4th hole to it becomes your limit on accumulation. You guys can analyze this to death but for as many years as I have been doing this, I have always counted ALL of the gaps in a pattern like this not how many 'moves' it takes to make the part. As a former machinist, I can tell you that nobody ever drills the first hole twice!
RE: How many angles are in a circular pattern?
Exactly as you said. The 360° is understood; therefore dimensioning the 5 angles and having the 360° implicitly understood is over-dimensioning, period.
I also agree with KENAT and ewh. This argument is moot, because if those angular dimensions are that important--use GD&T.
V
RE: How many angles are in a circular pattern?
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
http://www.despair.com/tradition.html
V
RE: How many angles are in a circular pattern?
How?
Example of how it DOESN'T:
5 x 72, with angular tolerance of +/-1
Hole 1: Perfect at 0
Hole 2: Conforming at 0 + 72-1 = 71
Hole 3: Conforming at 71 + 72-1 = 142
Hole 4: Conforming at 142 +72-1 = 213
Hole 5: Working counter-clockwise conforming at 0 (360) - 72-1 = 289
Angle between holes 4 and 5 = 76 degrees non-conforming.
Five individually conforming features result in a non-conforming and non-functional part.
RE: How many angles are in a circular pattern?
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
Just for the hell of it, let's punch in some actual numbers.
- 1/4 inch bolts with nuts
- 9/32 inch clearance holes
- 8 inch pitch circle
What are the required tolerances?Clearance C = Hole-Bolt = 9/32in - 1/4in = 1/32in = .031in.
Assume that the bolt is located precisely at the nominal position. If either (any?) holes shift C/2, the bolt will interfere with the side of the hole.
Assume that the maximum error occurs at 45° from the normal or from the tangent to the pitch circle.
At 45°, the maximum error in the normal or tangential direction is C/2sqrt(2), or .031in/2.828 = 0.011in.
Double this to get your pitch circle tolerance of 2×0.011in = 0.022in.
So far, so good.
My angular error is approximately linear error divided by half the pitch circle.
It is exactly arctan(2×0.011in/8in) = 0.16° (to two decimal accuracy :)
I do not know how accurately you can rotate a part on a fixture in a drill press, but I think this is getting pretty accurate. It reinforces your point that you cannot accumulate tolerances as you go around. The fifth angle imposes another tolerance control on the fifth hole. I am not so sure about the third hole.
The real point here is that it is not very practical to control holes using angular tolerances around a pitch circle. Either you must slot the holes, or you should plan on an X/Y positioning system such as a milling machine. For quite some time, I did not specify pitch circles on machined plates. I worked out the Cartesian coordinates, and I relied on ± tolerances.
Today, I assume that part will be fabricated on a CNC machine, programmed from some sort of CAD. I specify pitch circles again, and I use GD&T positional tolerances.
You might as well follow the ASME standard and say 5×72°.
JHG
RE: How many angles are in a circular pattern?
If you put the 5X without using GD&T then you have multiple conflicting interpretations of tolerance. To the best of my knowledge there should only be one.
It looks like one of these arguments that will be difficult to get everyone to agree on. For instance Drowoh says: I, in my infinite wisdom, believe this is not what the ASME explicitly says for all cases, so I disagree. 5X 72 is what it shows for all the examples using positional/GD&T, I haven't yet found a similar full examaple using +- dims in the standard, which makes sense as it says positional is preferable.
KENAT, probably the least qualified checker you'll ever meet...
RE: How many angles are in a circular pattern?
ALL dimensions must be met simultaneously. You state that the angle between 4 and 5 is not conforming...that's a show-stopper right there. It does not matter if some of the dimensions are conforming some of the time - ALL dimensions must conform and as you stated - the angle between 4 and 5 is nonconforming. What part of that statement is causing a problem? It seems to be a mixing of time and space here. The drawing must be met in it's entirety; all at the same time.
Example of how it DOESN'T:
5 x 72, with angular tolerance of +/-1
Hole 1: Perfect at 0
Hole 2: Conforming at 0 + 72-1 = 71
Hole 3: Conforming at 71 + 72-1 = 142
Hole 4: Conforming at 142 +72-1 = 213
Hole 5: Working counter-clockwise conforming at 0 (360) - 72-1 = 289
Angle between holes 4 and 5 = 76 degrees non-conforming.
The whole idea behind non-accumulating is to verify all of the increments, including the 5th which would not allow each one to be '72-1' would it? By tolerancing all of the spaces, you keep a 'creep' in incremental moves from happening.
ewh - what kind of double-talk is this?
"I am not measuring a part in it's final configuration, I am defining what the part will be."
Do you measure 'will' or 'is'? You've gotten distracted here. Time is not a factor and you cannot measure and verify a part's conformance until it has been made. I assume that the final goal of a drawing is a conforming, finished part and NOT a process!
RE: How many angles are in a circular pattern?
RE: How many angles are in a circular pattern?
How on earth did machinists make parts correctly before GD&T came along?
RE: How many angles are in a circular pattern?
KENAT, probably the least qualified checker you'll ever meet...
RE: How many angles are in a circular pattern?
I'm changing the way I do things ALL the time, because there is usually a better way to do them. I certainly don't reject things just because I've always done them a different way.
V
RE: How many angles are in a circular pattern?
I've yet to see an explanation or source stating that double dimensioning does not apply. SHOW ME THE STANDARD.
If tolerance accumulation is an issue, dimension it differently, or add a local note stating that tolerances are non-cumulative. I've have done that before. Again, as MintJulep posts, any problems arise "from the poor decision to use chained dimensions".
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
No, it's not. "Non-accumulating" in essence causes the 72 to become equivalent to a BASIC dimension. The "perfect" hole locations are calculated as 1 x 72, 2 x 72, 3 x 72 and 4 x 72.
The original question was not "Which is right, '4 x 72 non-accumulating', or '5 x 72 non-accumulating'". You are assuming design intent not in evidence in the drawing.
Laying out the part with that ASSUMPTION will make conforming parts that meet the designer's probable design intent. However that assumption IS NOT what the drawings posted originally call for.
RE: How many angles are in a circular pattern?
Uh, hope you are being facetious here, Mint? The part is NOT in compliance, because one of the angle gaps between adjacent holes is out of tolerance. The drawing tells you to measure 5 angles, in your example 4 angles are in tolerance, and one is not. Thus, the part is not compliant. Let's take a closer look at the shell game maneuver you tried to pull, my comments in italics next to your words:
"Example of how it DOESN'T:
5 x 72, with angular tolerance of +/-1 this callout tells you to measure the angle between adjacent holes, in 5 independent places, and verify them to be within +/-1 degree
Hole 1: Perfect at 0 this is not a hole-to-hole angle measurement, and is meaningless, as you can start measuring from any hole you want to...
Hole 2: Conforming at 0 + 72-1 = 71 angle measure #1, or between holes 1 and 2
Hole 3: Conforming at 71 + 72-1 = 142 angle measure #2, holes 2-3
Hole 4: Conforming at 142 +72-1 = 213 angle measure #3, holes 3-4
Hole 5: Working counter-clockwise conforming at 0 (360) - 72-1 = 289 angle measure #4, holes 4-5
Angle between holes 4 and 5 = 76 degrees non-conforming.
This last measurement would make angle measurement #5, and the fact that it is not conforming means the part is rejected. What Kim and I are pointing out is that in closed-figure angle measuring, you are dealing with a non-Cartesian coordinate system, and the "RULES" that you think apply don't. By closing the loop, and specifying ALL of the angular gaps, you ensure that the entire pattern is located to within whatever the angular tolerance is. My comment about land surveying holds, despite the snide comments from the unwashed. George Washington was smarter than most of you, since he knew that by measuring the last angle (called the closure angle) in his surveying triangles, he had a built-in error estimate for every triangle he surveyed, more importantly - he knew which angles he would need to re-measure in order to bring his total error under a given figure (e.g. the other guy's surveyor's error), which is everything in land disputes.
...and I'll let that last statement soak in, give it about 10 minutes and somebody is going to challenge my non Cartesian assertion...
RE: How many angles are in a circular pattern?
If you have five 72 degree increments and they are all controlled by the same general tolerance they CAN'T accumulate! Get it? Somewhere at least one of them would have to be out of tolerance to allow that to happen. THAT'S why you say "5X" and not "4X". That forces non-accumulation simply because you must measure every one and every one must be in tolerance.
If you don't understand this, please, please, please: read it over and over until you do before making another half-baked comment. This is such a basic idea and it's getting clouded with over-complicated ideas and statements.
RE: How many angles are in a circular pattern?
But, depending how cwdaniel wants to use the part and dimension it, it could be either figure. I can not suggest otherwise unless I see the mating parts. It is up to him.
cwdaniel,
I strongly suggest a copy of ASME-Y14.5.
Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 02, 2008)
RE: How many angles are in a circular pattern?
Regardless of what standard is followed in surveying, machine design IS a different animal and follows different standards. The insults hurled really don't help to clarify this situation.
If a drawing is to be interpreted by the standard, then that is what we have to go by, regardless of better methods. I agree with your logic, KimBellingrath, but it does not address the issue of double dimensioning per the standard. Revisiting the standard, it states in para 1.9.5.2 "Equal spacing of features in a series or pattern may be specified by giving the required number of spaces and an X, followed by the applicable dimension." That still leaves room for argument as to what is actually required, as we have seen. The figures referenced do call out ALL of the equal angles, but the intent of the figures is to denote the proper use of "X", and go against para 1.4(a) "Each dimension shall have a tolerance..." and para 1.4(c) "No more dimensions than those necessary for complete definition shall be given."
I feel that both sides of this issue have valid arguments, and if I weren't so stubborn, I'd concede and be done with it. As it is, I would have a hard time marking either method as incorrect on a drawing (though the tolerancing would still have to be addressed), so I'm going to do as others have suggested and use GD&T.
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
No matter. I've looked it over several times since posting this to review the references of others.
My original question was more of a drafting question than an analysis of tolerancing implications. Obviously I had no idea of the implications and the amount of fomenting of opinions this would generate. That being said, I think I've got my answer and learned a few things along the way. I'm leaning towards KENAT's camp. Positional tolerance gets 5x otherwise 4x. To avoid the risk of igniting some sort of international incident, I'll abstain from any further comment or opinions.
This has all been quite exciting though!
But, back to the drafting aspect of all of this. Earlier I conceded to be swayed from my current thinking. I posted another drawing that has been completely ignored in lieu of grand posturing, slander, and condescension.
Does anyone have any rational comments about my post of
7 Jul 08 13:08?
RE: How many angles are in a circular pattern?
V
RE: How many angles are in a circular pattern?
V
RE: How many angles are in a circular pattern?
I've had this "discussion" before with customers. My take on it is that if the holes are on the same centerline and that centerline goes through the center of the hole pattern, then one angular dimension is sufficient to define that centerline. Just don't ask me to back it up
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
I have used this dimensioning scheme on stepped parts or hole patterns as follows:
5 X 5.00
= 25.00
quite often without question or complaint as it gives you each increment plus a total which all have to be within the general tolerance.
RE: How many angles are in a circular pattern?
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
As to the "grand posturing, slander, and condescension", well it's not my fault if many of the other posters can't admit I'm right
VC66, 1.7.7 says that the right hand view is wrong. I think (hope) we can all agree to that. I would tend to extrapolate 1.7.7 to the circular case even if the 360 isn't shown, Kim and others disagree & choose not too. I think I'm right but can't be sure based on what is in the standard as far as I know it. Although, you've now got me thinking what happens if all the dimensions on the right hand view were basic, since the standard does show 5X72 when using basic, hmm.
Just invoke 1.4D I think the 5X72 is open to more than one interpretation when tolerances are taken into consideration, Kim & btrue disagree.
George Washington smarter than I, given what he achieved/was part of I can probably live with that.
KENAT, probably the least qualified checker you'll ever meet...
RE: How many angles are in a circular pattern?
If your company is large enough to write and maintain a standard for documentation definition, great, and you should adhere to the standard. If you are in compliance with Y14.5 or ISO or any other recognized standard,you should abide by their guidelines. Short of this you are pretty much on your own as is indicated here by the various interpretations placed on the sketches provided.
And the drawing should indicate the standard to which it has been prpared, if any.
RE: How many angles are in a circular pattern?
If you hold all five spaces to your tolerance, you limit the accumulation, but you do not eliminate it.
If your fifth hole is allowed to shift four times the angle tolerance, it can shift four times the angle tolerance.
Your method uses the first hole as nominal, and it controls the second and fifth holes to the angle tolerance. The third and fourth holes are controlled to twice the angle tolerance. This is better than the above case, but the caution about combined tolerances still applies.
5×72° is an non-English and minimal typing way of saying the holes are equally spaced.
JHG
RE: How many angles are in a circular pattern?
V
RE: How many angles are in a circular pattern?
Out of interest, or maybe lack there of in continuing this thread as is, is there a reason for you not to use GD&T, basic + positional, as shown by pretty much all the examples in 14.5?
KENAT, probably the least qualified checker you'll ever meet...
RE: How many angles are in a circular pattern?
How can there be more than one interpretation? You can measure the 5 independent angles, and determine if they are +/- 1 degree from the indicated value. Yes, the part is perhaps "over-constrained" (to borrow terminology from 3Dcad software), but it is not over-dimensioned, nor un-buildable with the tolerancing scheme shown in vc66's left-hand sketch (ignoring the ambiguous 0-degree or 360-degree measurement). If the values for each dimension can be independently measured it is not over-dimensioned. Whether it is against "para 1.4(c) No more dimensions than those necessary for complete definition shall be given." is open to intrepretation - if the designer wants the constraint given by the dimensioning scheme shown, he dimensions it as shown, or alternatively uses GD&T to constrain the tolerances to a more rational system.
By the same token, I do not think that vc66's right hand sketch is truly over-dimensioned for all cases, since again, each dimension can be independently measured (the fact that one of the dimensions may not vary independently without possibly affecting other dimensions is immaterial, we don't specify how it's made, just how it is to be inspected, right); it may or may not be over-dimensioned, depending upon how the designer wanted the tolerances to accumulate (or not accumulate), thus the vagueness of "para 1.4(c) "No more dimensions than those necessary for complete definition shall be given." It IS over-constrained, again to borrow terminology used in the 3D-Cad world, and I would agree that both sketches, IF he had placed basic tolerances boxes around the dimensions, would/could be construed as over-dimensioned, but then the spec. requires you to put the 5X in the circular pattern for GD&T (or does it?).
But there are times when that right-hand sketch may be required by a designer (who is essentially saying, I need 5 steps within some tolerance, and the whole part has to fit within this gap). Yes, it requires a machinist to do some thinking, and is more complicated to make than a stepped shaft, but if the part requires those tolerances, it's his job to stop whining and figure out how to build it.
...and, all kidding in front (the opposite of all kidding aside), Kenat and ewh and et. al. on this forum should know that my comments re that rebel George are done with tongue firmly, rigidly in cheek ... plus or minus 1/2 cheek. :P
RE: How many angles are in a circular pattern?
KENAT, probably the least qualified checker you'll ever meet...
RE: How many angles are in a circular pattern?
There you go.
The btrueblood/kimbellingrath interpretation that each hole must simultaniously conform to the angle from its adjacent two holes violates that provision of the standard.
The angular location of each hole can be fully defined with one and only one angular dimension.
As I wrote earlier, if you want holes located at 0, 72, 144, 216, and 288 degrees, then those angles should be dimensioned. Or specify 72 as basic, and use GT&T to control the location.
RE: How many angles are in a circular pattern?
... which brings me back to my question of 8 JUL 08 09:20, "are the holes located and can the part be made using 4X 72°?" The answer is yes. They may not end up where you need them (the tolerancing issue), but their positions ARE fully defined. If this is insufficient due to tolerance accumulation, don't use chain dimensioning. Any additional dimensions are superfluous, and result in double dimensioning.
OK, I've had enough. I guess it's time to agree to disagree.
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
RE: How many angles are in a circular pattern?
And yet the same spec. shows "5X 72 degrees".
Kenat: "btrue, so you're saying you disagree with 1.7.7 in y14.5? "
Kenat, you should know by now that there is a LOT of things in the holy Y14.5M that I disagree with. But, in this case, vc66's sketches never invoke Y14.5M, and (I thought) we are talking more generally about +/- tolerancing and double-dimensioning. I maintain that the right-hand sketch has a solution, and can be manufactured, even though its tolerancing scheme is confounded. If Y14.5M were to be invoked on the drawing, then the author would deserve several dope slaps for not using 5.0 as basic dimensions, setting one end or face as a datum, and controlling profile or flatness or parallelism of the surfaces to within whatever tolerance is required.
Also, although the spec. is next door, I will bet you a pint that 1.7.7 has the word "should" not "shall", so maybe I really don't disagree.
But, no, I'm playing devil's advocate here for the most part, and agree (wholeheartedly) that GD&T is the way to go, as there is/will be LESS disagreement on what is 'the design intent' using the spec. than there is without it.
All of my drawings go out with Y14.5M invoked by general note. But, yes, I can, do, and will still, "violate" Y14.5M whenever I
pleasefeel that it is necessary to achieve a design purpose. And add explanatory notes describing what is required. And expect to hear from inspectors, etc. So, I try NOT to do it very often, and am trying to update hundreds of older drawings with dimensioning schemes much more nefarious than the one in vc66's sketches, often behind the back of the authors (my seniors).As far as using 5x72 degrees or its equivalent, in BASIC dimensions, as part of a GD&T position tolerancing scheme, I also see no problems with it either way. Because both 4x72 and 5x72 will produce the same hole pattern, since basic dimensions are exact and thus there is no ambiguity, you will achieve the same result. Whether or not it is "over dimensioned" becomes something of a moot point, and affects drawing clutter or "style" more than whether or not work can proceed.
RE: How many angles are in a circular pattern?
At least, in the copy of the '82 spec. I was able to lay hands on quickly, it's pretty clearly spelled out as a "DON'T".
Your pint awaits you in the pub, Kenat.
RE: How many angles are in a circular pattern?
No shoulds about it, although as VC66 doesn't explicitly reference 14.5 on his sketch or in his post then I doubt you oweing me a pint is enforcable in a court of law
Rules, laws or in this case standards are for the obedience of fools and the guidance of wise men, or something like that. I'm pretty sure I don't fall in the wise category and the more I get to know the standards the more reluctant I am to contravene them, however maybe you're wiser than I
Enough of this though, it looks like both sides are entrenched in their positions, and it sounds like the OP thinks he has his answer so I should just let it go like I tried to do before.
KENAT, probably the least qualified checker you'll ever meet...
RE: How many angles are in a circular pattern?
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
Doh, I wasn't going to post again.
KENAT, probably the least qualified checker you'll ever meet...
RE: How many angles are in a circular pattern?
Imagine that! A standard with internally conflicting requirements.
As is my prerogative as an obstinate cuss, I choose to pay attention only to the requirements that support my view of the world, and ignore those that don't.
RE: How many angles are in a circular pattern?
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
KENAT, probably the least qualified checker you'll ever meet...
RE: How many angles are in a circular pattern?
Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 02, 2008)
RE: How many angles are in a circular pattern?
KENAT, probably the least qualified checker you'll ever meet...
RE: How many angles are in a circular pattern?
mechanical drawing 101:
if you have 5 holes in a circular pattern, you also have 5 spaces! how could you think any differently?
point to one hole and say (5) __ dia holes on a __ dia b.c. equally spaced. add your gd&t, perpendicularity, etc. and the indexer on your drill press will put the holes in. then inspect the part.
teddykaye
RE: How many angles are in a circular pattern?
V
RE: How many angles are in a circular pattern?
RE: How many angles are in a circular pattern?
What most can agree on is that using GD&T it becomes a none issue.
Lets just leave it there unless the 14.5 committee want to have a special meeting just to bottom this out in time for the new version of the standard.
KENAT, probably the least qualified checker you'll ever meet...
RE: How many angles are in a circular pattern?
"What most can agree on is that using GD&T it becomes a none issue."
I think we can ALL agree on that.
RE: How many angles are in a circular pattern?
Enough already even though I'm probably the worst offender now for dragging on this rotting equine carcus.
KENAT, probably the least qualified checker you'll ever meet...
RE: How many angles are in a circular pattern?
C'mon, we can make it a century here if you just keep playing. There's room in there for one more pint, it's Friday, the missus don't expect ya home for hours anyways...
RE: How many angles are in a circular pattern?
We may have to buy our own pints...
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
V
RE: How many angles are in a circular pattern?
RE: How many angles are in a circular pattern?
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
Mike
RE: How many angles are in a circular pattern?
RE: How many angles are in a circular pattern?
RE: How many angles are in a circular pattern?
The Sketches don't. So my assumption was the same, that is why my pick was Fig A.
memiles,
Did I miss something? Where are those dims from? How can two different dim's be dbl dim?
Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 02, 2008)
RE: How many angles are in a circular pattern?
Screwed up, tired.....
sorry
Mike
RE: How many angles are in a circular pattern?
Without a standard, it appears much more difficult to determine if something is in compliance with the unidentified.
This should be the century mark, btrueblood.
RE: How many angles are in a circular pattern?
Fair enuff, but it's still a complete enough description of the hole pattern, showing that you dimension all the holes and all the angles...later on in the same spec. should be a similar pattern dimensioned with GDT (position and basic dim's.), and again showing 8x angles for an 8x hole pattern...
No, the actual question (how many angles must be dimensioned) never gets addressed directly. Never thought it needed to be, until this thread came up.
Weavedreamer, you win the prize.
RE: How many angles are in a circular pattern?
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?
However I'll get you a drink anyway as this post is something like 4X (or is that 5X) as long as it needs to be by now, I should slap myself for posting on it again.
KENAT, probably the least qualified checker you'll ever meet...
RE: How many angles are in a circular pattern?
So, the standard deliberately shows incomplete tolerancing, that I understand, the figures are intended to supplement and illustrate. But, you are saying that they show deliberately misleading examples, such as showing 8x angles for 8x holes in a circle?
What is your take on this, ewh, how should we grunts grinding out drawings dimension our hole patterns; should it be 4x or 5x?
Given that the purpose of the standard is to allow generation of a graphical communication tool (dimensioned drawings), for the std. to make the above statement pretty much renders the whole damn thing nearly meaningless. Most of us can, do, and will continue, to look at the pictures to provide clarity and examples. Otherwise, what else have you to go by?
RE: How many angles are in a circular pattern?
KENAT, probably the least qualified checker you'll ever meet...
RE: How many angles are in a circular pattern?
RE: How many angles are in a circular pattern?
As for the illustrations, again per a strict reading of the standard, they are only relative to the text which refers to them, and practices other than that based on them is assumption only. The text rules and the figures only illustrate the text.
As far as making "the whole damn thing nearly meaningless", I think you are exagerating a bit.
All of this is a moot subject since the standard is not being invoked.
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: How many angles are in a circular pattern?