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本帖最后由 datafield 于 2013-2-4 00:40 編輯
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| metaldork (Agricultural) | 8 Mar 12 12:53 . t. _: h/ R" I' C b/ v
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H% U4 t% t) ^5 I: wCan anyone please clarify if a perpendicularity call out is controlled by a basic dimension or not? In other words is the tolerance zone centered on a basic dimension? * `! R- s. v( z. E( q! [7 N2 e3 n# u
哪位可以幫忙介紹一下，垂直度要求，是否須與理論尺寸相關聯？或者說，垂直度的公差帶，是否以理論尺寸為中心？5 }5 G! ?4 n- a9 }
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| CheckerHater (Mechanical) | 8 Mar 12 13:03
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No, it is sufficient by itself. ; L/ I3 V" T' B2 ~6 N
不，垂直度本身已經夠了。
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0 j# }( a3 W+ _& Y7 P0 {- zIt MAY be used together with basic dimensions when used to refine the Position.
0 y1 m. W0 e# Y% o- ~! J當然，在定義位置的情況下，也可以與理論尺寸聯合使用。: \0 T+ U0 Z: ?/ r4 p( l5 G* g
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]! x# {! m( [| powerhound (Mechanical) | 8 Mar 12 13:42
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No, the tolerance zone moves with the feature being controlled. 不，公差帶隨著其控制的形體而移動。
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| metaldork (Agricultural) | 8 Mar 12 13:56
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The surface is dimensioned from a parallel surface ...would the perp callout control the dimension and if so should it be basic?
- f& v! d$ o" L5 B平面從互相平行的另一個面來定義尺寸……會要求用垂直度來控制尺寸嗎？若是，尺寸要為理論尺寸嗎？ |
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[6 |% n. b& n" F| CheckerHater (Mechanical) | 8 Mar 12 14:17 4 f0 w1 G7 D6 f+ i; a
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There is a difference between Perpendicularity and Parallelism. 垂直度與平行度，是不一樣的。* |# R( m8 e1 r' g2 Y
Even in case of Parallelism the dimension can be toleranced; the Parallelism will refine the tolerance. 就算是平行度，尺寸也可以標明公差；平行度將進一步限定公差。
$ |1 q! C/ I7 ~& yIf I don't understand something, please provide a picture. 如果不太明白，請給圖示意。
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![]() Belanger (Automotive) | 8 Mar 12 14:35
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First, there is an implied basic dim with perpendicuarity. It is the 90 degree relationship to the datum. That's not the kind you were thinking of, but I feel obligated to mention it. 首先，垂直度有一個默認的基本前提，即：與基準的90度關系。這不是你所想的，但我有義務得先申明一下。* i$ D5 e& e! D: P& c
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You ask about locating the perp tolerance zone. That should never happen with basic dims. The perp tolerance zone can float freely within whatever other constraints there might be. 你問的是垂直度公差帶的位置。這與理論尺寸無關。垂直度公差帶的位置，可以在其它約束里自由移動，如果有約束的話。
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IOW, the per tolerance never controls the distance from the parallel surface. There should be something else to do that, such as plus/minus. The perp doesn't get added to that; it must operate within it. 哦，平行平面的距離，不受垂直度控制，而受控于其它因素，比如+/-。垂直度不會擴大它；垂直度必須在此范圍內。
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/ g% `6 ~9 P7 M, C% p! SJohn-Paul Belanger
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! l' \5 a8 D4 U) YGeometric Learning Systems
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| dgallup (Automotive) | 8 Mar 12 14:38
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| The surface can be dimensioned from a parallel surface and still have a perpendicularity to a datum that is normal to both surfaces. The dimension will control location and to the extent that the envelope principal applies, form. The perpendicularity must be a refinement of the dimension tolerance, typically half or less. 某個面，可以從與其平行的另一個面來標注尺寸來定義距離，同時，可以標注垂直度（基準與此兩面都垂直）。尺寸，按包容原則來控制位置。垂直度公差，必須小于尺寸公差，通常為尺寸公差的一半或更少。 ----------------------------------------
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1 G2 N5 G" S: k% C+ X5 V| axym (Industrial) | 8 Mar 12 15:09 : I$ i3 T5 }7 l- }
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metaldork," E- a) T: ^& L* Z- S
' z, P P7 h6 ^ rThe way I like to look at it is that the Perpendicularity zone can always freely translate - its location is never controlled relative to anything. So the Perpendicularity zone is always completely independent of any linear dimensions (basic or directly toleranced) connected to the considered feature. 我認為，垂直度公差帶，是可以自由移動的——它的位置，不受任何約束。故，垂直度公差帶，總是與被測形體的線性尺寸（理論尺寸或直接標注公差的尺寸）相互獨立的。
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dgallup,
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In the scenario you described, the Perpendicularity doesn't have to be a refinement of anything. The directly toleranced dimension doesn't control the squareness, so the Perpendicularity tolerance doesn't need to refine it.Evan Janeshewski
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| pmarc (Mechanical) | 8 Mar 12 15:13
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I am with J-P on this, the only basic dimension that applies for perpendicularity is basic 90 degrees to the datum and it is usually not shown on a print due to implied basic 90 deg dimension rule./ B5 a" [) @/ \
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dgallup,; x3 o6 x% w( ? r
You said: "The perpendicularity must be a refinement of the dimension tolerance, typically half or less.". o/ p- K: v8 z: i
I would be careful with that. If perpendicularity callout is applied only to one "side" of a dimension, its value can be whatever one can imagine (assuming there is no general angular tolerance shown on the print that would control a relationship of the other "side" of the dimension relative to the datum).
! V- A; X+ [# OThe other story is when there are two perpendicularity callouts applied to both "sides" of the dimension. In that case, my vote is their values can be as big as the dimension tolerance (and not half of it).
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/ F/ }$ l, N! [0 {- x| CheckerHater (Mechanical) | 8 Mar 12 15:57
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Evan,
/ d g& d& J% A# f! d" X7 QCould you please clarify: Do you believe that perpendicularity tolerance zone can "freely translate" OUTSIDE of linear dimension /position tolerance zone?: A* S" g5 q' }+ ]/ J
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$ ]7 ?' p( V" z6 @| Belanger (Automotive) | 8 Mar 12 16:39
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CH, picture a U-shaped bracket -- sort of like field-goal posts. Now take both vertical posts and bend them 20 degrees to the left. Are they within the size (width) tolerance? Yes. Is the post on the left within its perpendicularity tolerance to the ground? No.
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: P0 m7 u# C. k x1 C8 GSo there is no relationship between the tolerance number for the size across the posts and the tolerance number chosen for the perpendicularity.
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2 y+ v# E/ n1 E ^" E1 oSorry for jumping in, Evan. Feel free to modify my explanation  John-Paul Belanger
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| axym (Industrial) | 8 Mar 12 17:54 + X8 `! i* e- f" Y
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Quote (checkerhater):"Could you please clarify: Do you believe that perpendicularity tolerance zone can "freely translate" OUTSIDE of linear dimension /position tolerance zone?"
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CH,* u l1 G* p" w' l; a9 N! d: r
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Quick answer, yes. But of course there's more to it.5 W. _0 B4 C. U$ Z+ ]
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If we think purely in terms of the tolerance zone mechanics, which I always try to do, then the Perpendicularity zone is allowed to translate outside of the linear dimension / Position tolerance zone.
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! }* O; f0 M/ j: d. CIt is true that the feature might not conform to the Position tolerance if the Perpendicularity zone had to translate partly outside of the Position zone. It definitely wouldn't conform if the Perpendicularity zone had to translate completely outside of the Position zone. But that is a different consideration.# ^& S( g; ]7 |/ A2 o- ?/ J% Y
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The way I like to look at it is that the Position tolerance and the Perpendicularity tolerance are independent requirements, that can be evaluated independently of each other. This is the only way that I am able to make sense of it all. Some GD&T books state or imply that the orientation zone must float within the location zone, but to me this is an oversimplification. It is possible for part of the orientation zone to extend outside of the location zone, and still have the feature conform to both tolerances.Evan Janeshewski
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| CheckerHater (Mechanical) | 9 Mar 12 6:32 9 ?: [+ V6 W3 B
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Thank you Evan,+ i6 P7 X+ A$ N A2 ^
Appreciate straight "Yes" - rare thing nowadays.
) c$ k# L0 h h& _+ wUnfortunately I am not convinced. Imagine the hypothetical situation:# _# V, E3 O3 F6 k P7 C
You are using some sort of measuring machine. You find out that the axis of certain hole (or boss) is laying WITHIN perpendicularity tolerance, but OUTSIDE of position tolerance.# `0 Z/ q0 K" H3 T9 v
Would you suggest the part to be accepted or rejected? (Another straight Yes or No will be appreciated)
' L% H8 I+ I7 GI personally believe that your position and perpendicularity zones should at least partially overlap. (It will create some interesting conditions that probably were never fully documented, but nevertheless).
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Joan-Paul,
8 E5 J7 i0 N, O7 UYour argument appears to be far stretched and borderline cheating (Sorry)" |$ u/ Q) h% `, k" d
You said it yourself: "Is the post on the left within its perpendicularity tolerance to the ground? No." So what you describe is "bad" part that should never be accepted in the first place. The purpose of GD&T is to describe the parts we will accept, right?0 T' A# l" X9 X4 A3 k
Another stretch: "tolerance number for the size across the posts". Most people would consider "fork" being two features of size, not one. Is space between two holes feature of size?9 A F+ F4 A' A6 L, n# e- F& n6 r
So your argument basically is: "If we can make bad part from ambiguous drawing, then there is no relationship between the tolerances". Sorry, but I am not buying it.9 J7 ^; e! s1 v, X1 I( T3 ^
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| Belanger (Automotive) | 9 Mar 12 7:03 # ~5 b& L2 a, Q8 B! [! _3 g
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CH -- I don't quite understand your concern. First, yes, the space bewteen the posts is a feature of size; so is the outside of the posts. But my example was really meant to discuss surface perpendicularity (I just used the posts as a visual example. Sorry for the confusion.)
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) `9 T1 r* _0 o7 U# D6 ?9 Q/ @- q6 R"Is the post on the left within its perpendicularity tolerance to the ground? No."
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The reason I wrote that is that many people think that a size dimension also controls orientation -- that's not true! So I'll rephrase it differently: Two vertical surfaces can lean in the same direction and still be within perpendicularity tolerance. They are also within the size tolerance. But there is no connection between the tolerance values for the perpendicularity and the size.John-Paul Belanger
6 C# Y5 H( q- C/ P( ZCertified Sr. GD&T Professional
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9 T! _+ ~, q$ d+ l# Z0 T. y| CheckerHater (Mechanical) | 9 Mar 12 7:54 3 B7 W1 _% h$ A+ ~! V- ^& f- \
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Thank you JP, we are getting somewhere.# _# L5 C& x% p0 X/ x
Let say, we have FOS with perpendicularity requirement added. The size tolerance is .001, the perp. .100. But they both affect VIRTUAL CONDITION, right? Now, what if we add position requirement to our virtual condition?/ K" i9 R3 z, ?' _$ b/ d, Z& p
You see, I never said perpendicularity is a refinement of size. But I still insist on the following conditions: Perp. tolerance zone being outside of position tolerance zone makes no sense. Perp. tolerance zone being larger than position tolerance zone makes no sense. It may be legal though.- B8 s3 U7 f" J* v: K: U% S* h
When you have 2 FCFs applied to same feature, their requirements have to be met together (I didn't say "simultaneously"). If perp. tolerance is .100 and position is .010 position requirement controls perp. indirectly and makes perp. requirement useless.
5 g4 p. M2 G' s6 L+ N/ J) @1 J! KSo, when used together with position requirement, perpendicularity only makes sense when perp. tolerance zone is smaller than position tolerance zone, and both tolerance zones overlap at least partially. To me it means "refinement".
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| pmarc (Mechanical) | 9 Mar 12 8:57 # B2 A) T; t3 ~3 N
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Apologies for jumping into main topic.
3 }/ V, Q5 x+ [# lCan you have a look at attached picture?- ~4 G3 @* a" s) B
http://files.engineering.com/getfile.aspx?folder=a7879b3a-d0d7-459f-b9ac-829eb08891da&file=surf_perpendicularity.JPG; ~3 e: t0 G* F8 N2 {9 y# W
How big can those perpendicularity tolerance values be, assuming they both have to be equal? Is there any limit or not? Thanks.
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| fsincox (Aerospace) | 9 Mar 12 9:15
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I believe it is acceptable to use a space between to pins say as a feature of size, right?
, P( V) `6 R! p$ M$ K) h8 uFrank / R1 F6 | k, S* ~# `
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| CheckerHater (Mechanical) | 9 Mar 12 9:29 ; p6 v" ?/ {5 ]
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Frank,# }* V. U. l# Y7 j$ _1 M
Yes, but it will make them more ambiguous, than 2 FOS with position requirement, right?
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pmarc,& U6 X* y' R/ X- N3 L
What do YOU think?
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| CheckerHater (Mechanical) | 9 Mar 12 10:03
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pmark,/ ~& k. Y3 `3 I0 h X! t9 B
You are a genius - I think this is exactly what OP was asking: do you use basic dimension to control perpendicularity of parallel elements.
; W# t+ v( Q) w+ b+ @0 rI would use basic dimension with profile to control the whole contraption. That will also make it less ambiguous.
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6 @& ]- Z* I" d% E; N a| pmarc (Mechanical) | 9 Mar 12 10:04
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CH,( U" I8 G( F ~
You are asking what do I think about my sketch or about your modified version of my sketch? Or is your sketch showing only one of situations that may occur for my tolerancing scheme?
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! L; R; e# |# v3 L8 o$ W$ n' W% t| fsincox (Aerospace) | 9 Mar 12 10:20
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Sure ideally all should be controlled, that is right out of the book. Frank3 c; J0 f/ j4 s* ?
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$ [# q7 H( F, X( s| CheckerHater (Mechanical) | 9 Mar 12 10:22 % h# t1 o5 H) J
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Actually both (or all three?).9 r6 Q* T( p u: v _
I feel like using direct dimensioning may create ambiguity here. There is a reason ISO calls it "two-point dimension".
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| CheckerHater (Mechanical) | 9 Mar 12 10:36 " _" n/ s: a% n) x2 K8 y
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Frank,
' ]/ P6 p3 n% e X. o: J% FOff-topic, but since you brought it up; have you ever seen round hole dimensioned to the edge rather than center?0 d* |$ @) O3 e$ E9 A! o, A! l3 q; X
I did, I was even forced to do it myself, I still don't like it. ![]()
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| fsincox (Aerospace) | 9 Mar 12 10:55 0 M* i# a3 _- F% d* U r
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CH,
( V& S( {$ [" H- \* d7 p& \/ m$ HAre you kidding? I cut my teeth on that. It is what I was looking to GD&T to help me escape from. ;)) W3 A1 d; w% l
This thread has confused me a bit with the whole perpendicularity zone centered, center implies a location. Seems like at least part of the perpendicularity zone must be in the location tolerance zone or you would just move it.0 u# ~1 z3 b8 D' F3 L" t2 x# W' ^
Frank
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發表于 2012-12-25 16:54:48
