symetrical symbol application
symetrical symbol application
(OP)
Can somebody please describe how the symetry symbol is used in a drwaing. where it is placed and the correct way to display the view using it? so far i've been told a couple of different ways but would like to find the most common usage.
thanks in advance
thanks in advance





RE: symetrical symbol application
Try forum1103: Drafting Standards, GD&T & Tolerance Analysis.
In the ASME Y14.5M-1994 standard, it is shown applied to a symmetrical dimension on page 155, Figure 5-61. The feature control frame contains the symmetry symbol, the tolerance, and the datum the feature is to be symmetric across.
What are you trying to do?
JHG
RE: symetrical symbol application
enabling U to dimension without originating at an edge or showing allot of dims and still conveying design intent.
sample i referred to was in the design and drafting standards which our company uses.
thx again
RE: symetrical symbol application
A picture will help...and spell check.
Chris
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RE: symetrical symbol application
My big problem with the symmetry symbol is that I cannot see a requirement I need to specify that would be described by symmetry. An actual feature I want might turn out to be symmetric, but that is not what I am after.
You have a feature located to a datum. The feature has size tolerances as well as location tolerances. You can use the true position tolerance to locate the feature, regardless of where the datum is. True position controls parallelism as well. You can use profile to control the size and position, again, regardless of where the datum is.
If the datum is at your feature, is there any reason why it cannot be your feature. You cannot get any more symmetric than that!
GD&T is a language, not a procedure. What are you trying to accomplish?
JHG
RE: symetrical symbol application
thanks for all your help.
garyrinvegas
RE: symetrical symbol application
Aha! In ASME Y14.5M-1994, this is figure 1-33.
This is not a feature control question. This is a drawing notation question. The notation on Figure (1-)33 looks fine to me. If someone wonders what the heck you are doing, you can point them to the standard. This is much better than telling them that this is how your uncle Bob did it back in the seventies.
What are you actually saving with all this? If you were on a drafting board, you would save drawing time. In 2D AutoCAD, you would draw one half of your shape, and mirror it. In 3D CAD like SolidWorks, you have to model the whole thing, and you have several mirroring resources to make this easy. All you can possibly save is space on your drawing. The moment someone has to come to you to explain the drawing, you have wasted whatever time it is you tried to save.
JHG