Beginner Question Cutting on an angle

In drawing a simple cylinder how can I cut it on an angle. Take for example the hood on each light of a traffic signal or on a railroad signal. I draw two circles and push down on the middle to create a hollow cylinder. Now I want to cut the cylinder on a 45+ degree angle to form the hood over the light that is used to prevent the sun from distorting the color of the light. Here is the prototype of what I want to draw and 3D print.

Draw a rectangle and rotate it to the angle you want so it passes through the tube. Then use Intersect Faces to intersect the rectangle with the tube and erase what you don’t need.

Model railroad stuff?

  • Make a component of the cylinder.
  • Draw a rectangle at the required cutting angle and place it in the desired place overlapping the component (draw it outside the component so that you can move it around without affecting the cylinder yet)
  • edit->cut the rectangle, open the component for edit, and do Edit->Paste in place.
  • select the cylinder and rectangle, right-click and choose Intersect Faces with…Selection
  • use the eraser tool to clean up the parts of the cylinder beyond the cut and also the now extraneous rectangle.

Depending on the size of the parts, you may have to use the “Dave Method” to avoid issues with SketchUp deleting small faces.

Assuming this is for a model railroad, you could model at full size (assuming you know the real world dimensions) and then scale the model down by the required factor. For O-gauge, for example, scale down by 0.0208. This saves you having to calculate all of the scaled dimensions. I’ve done this for our N-scale stuff.

1 Like

Thanks guys that I will try. Yes it is for PRR position light signals for my layout. DaveR, the only concern I would have using prototype dimensions is getting too thin. The signals are fairly simple from a dimension standpoint and I have prototype plans so not much trouble to use scale dimensions so as to control minimum thickness my printer can handle. I work generally in 0.18 mm layers to get smoother prints. I am using a LulzBot Mini first version. They do have a new nozzle with half the size but it is $300, so not for a while.

Understood on things getting too thin and on the nozzle. Save your shekels. :wink:

The scale may be too small for it to matter, but you could make that cutting plane more akin to the profile of a light hood for a more elegant look?

Also, showing another way to get that angle if the intersecting/cutting is too tricky.

Thanks again and a video to boot. You guys are the best. I will give it a try.

Each signal head has 7 hoods. Can I do one, make six copies, and then attach to the back plate?


Yes. In fact that makes the most sense.

I would make the one in the center, copy it horizontally to the side in each direction and then use Rotate/Copy to make the other two on each side.

Another way with the extension TrueBend



@Cotty probably shows a result that would be closer to the way the original was made since the original hoods would likely have been formed out of sheet metal instead of cut from a tube.