symetrical symbol application

[garyrinvegas]

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

 

[drawoh]

garyrinvegas,

Try forum1103.

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

 

[garyrinvegas]

HARD TO EXPLAIN. show a view with center line and above and below the actual object use the symetry symboll (two horizontal lines) just outside the object lines. one on each side of the object

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

 

[ctopher]

I suggest asking in the appropriate forum as drawoh suggests.
A picture will help...and spell check. ;-)

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 08
ctopher's home (updated Aug 5, 2008)
ctopher's blog
SolidWorks Legion

 

[drawoh]

garyrinvegas,

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

 

[garyrinvegas]

figure 33; page 12 of ansi Y14.5 19982 has what I am trying to do. But have found out they don't want to dimension these parts that way. different strokes.
thanks for all your help.

garyrinvegas

 

[drawoh]

garyrinvegas,

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