Extruding symmetrical elements results in asymmetry?

curtis_vancura

I have a gouge blade (90 degree with 15 degree rake angle) that I am trying to model, and asymmetry is popping up.
The two cut sides should be the same... but one is 90 degrees, and the other has the proper angle.
I have spent hours trying to understand why, and would like some help.
https://cad.onshape.com/documents/5eb8957c9916dd8a2cc31ea6/w/fecf0985abc589292f81dbf9/e/32c73b253da8ed7d3f84b844

...also, a link to how to post in this forum (images, links, etc.) would be helpful...

Thanks, Curtis

curtis_vancura

Thanks mahir, this is the fix! 

curtis_vancura

Might this be a bug?

jakeramsley

When you look normal to sketch 6 (before the extrusion) you can see that one of the edges of your profile lines up correctly with the edge of the part and the other does not.  When cut away, this will cause it to skew.



You'll want to remove the vertical/horizontal constraints of the sketch, then make the lines coincident with the edges so that they are what the projected edges would be.  From here it should cut at the 15 degree angle.

bruce_williams

On posting links & images.  Maybe @lougallo could chime in if there is help on forum use - I do not find.  However, here are a couple tips.

To attach image:  Choose the image icon (next to attach file) and paste in a copied image (it does not have to be URL).

You can add links to text like this - Extruding symmetrical elements results in asymmetry?   By selecting the text, then the link icon, and paste in the URL.  Here is picture of steps -

curtis_vancura

I have updated the shared part to show the issue more clearly. None of the sketch 6 edges are coincident to any edge of the part, as can be seen.

...although there is symmetry in the sketch and its plane in relation to the part, but there is a dotted line (sketches 4 and 5) that shows asymmetry. I have tried to make two separate parts, but was unable to get the profile as desired.
Why does the extruded part become asymmetrical? The edge should cut a 15 degree angle on both side walls (following the dotted line), or at least that is what I want, and that is what this part becomes in real life, as cut.

Where is the mistake?
Thanks for looking at this, I really need some help, it is beyond me at this point...
-Curtis

mahir

The mistake is in the direction of one line in Sketch6. It is set to be horizontal, but it needs to be oriented symmetrically with the other leg of the "L". Take a look at my link for the fix. Also, it would probably be easier to accomplish this same geometry with two cuts, one on each leg. Or even a chamfer feature.

https://cad.onshape.com/documents/1f870af61556d44bac1bb194/w/7f8fb2db151dfb128c69a9f8/e/9a243b77fafa1077caaebdf4

curtis_vancura

Thanks mahir, this is the fix!