Technique for extruding from opposite faces

I’m trying to draw a scroll saw rocker arm.

I drew the geometry on a flat plane and then tried to extrude to the desired thickness from each side. One side extrudes well but when I go to the reverse side, the closed face has disappeared. If I redraw lines I can close the face and extrude but that seems very cumbersome.

I would appreciate any help with making this easier. Here’s the skp file.
Excalibur rocker arm problem.skp (143.9 KB)

On phone so can’t look at your model. As a guess delete the surrounding plane and you should be able to extrude in one hit.

If I were modeling this I would give the arm the thickness along the center before adding the details to the sides. Since it is symmetrical I would model one half of it and then copy and clip it to make the other half.

I tried it that way but I found I had to redraw the geometry on the reverse side and that seemed awkward. When I tried it this way I saved my flat plane geometry in case I have to start over.
Excalibur rocker arm1 flat plane with geometry both sides.skp (106.7 KB)
Excalibur rocker arm1 flat plane with holes marked.skp (93.9 KB)

You could copy the geometry from one side to the other or you could just model half, then copy and flip.

It looks like you started by drawing a 2D version on a helper face and then began pushpulling the various parts? That’s a good way to keep the initial drawing all on one plane, but you need to delete or isolate the rest of the helper face before doing pushpull because when you pushpull an interior shape on a face, SketchUp assumes you mean to cut an opening and deletes the starting shape. You can avoid this by pressing ctrl (alt on Mac) before doing each pushpull.

lost face

As @DaveR notes, it would also be faster to model half and then flip a copy to create the other symmetric half.

Having now looked at your model the most straightforward answer is you need to look at the fundamentals available at the campus.

1 Like

Thanks for the tip on pressing ctrl when extruding to avoid opening up the face on the opposite side. It helps a lot with my labor intensive technique of developing geometry on opposite faces.

I will be following up on Dave’s suggestion to work on one face and then copy the geometry to the opposite face. Sounds like that should cut my work in half.

1 Like

Pun intended?

Seriously though, whenever a part has symmetry you can reduce your work and your mistakes by doing half and then mirroring.

Point taken. I was just reviewing the fundamentals course, and I see in the section on the push/pull tool that they identify the ctrl modifier key with push/pull to leave a copy of the surface. It seems obvious now but I know I missed that before.

You do have to be careful using Ctrl with Push/Pull because it can leave internal faces which are a problem for 3D printing.