Intersection od 2 cilinders


Continuing the discussion from Welcome to the SketchUp Community!:


wait, what is the discussion? cylinders or the discourse forum?


I’ve been looking for this topic and I found instructions. The thing is sometimes it work sometimes it doesn’t- Most of the times, however, I get the up intersection but not thr lower one.
The work is one large cilinder horizontal, crossed withe a smaler diameter cilinder vertical.
I draw both cilinders, separatly, then group each one, then position them, the smaler diameter one across the bigerr one.
Then I select rhe biger one and click Insertion. I then erase the smal one.
The result changes any time, although I perform the same operations.

  1. No insertion line is set on the big cilinder, therefor it cannot be edited:
  2. Both lines are set on the big cilinder and the work can be dane (very few times))
  3. Only the uper intersection can be edited, so I can complete the upper hole but not the lower one (90% of the times).
    I realy would like to know why this strange random behaviour hapens.


Your intention is to cause the two cylinders to cut each other and then to use some geometry from each cylinder to make the final shape (which I presume is to be a hole in the larger cylinder, although you didn’t say). The point is, in order to interact with each other (cut each other and then fit together to make an integral object), both cylinders must be in the same context when you invoke the Intersect command. “The same context” means the same group or component or in no group or component at all. When you group the cylinders separately, they can’t operate upon each other.



In fact I want the two holes in the large cilinder. I have tried to explode both groups and then make a single group.
Some times it works, sometimes it doesn’t. Most of the times, as I said before, I manage to do the upper hole but not de other one.
I don’t understand this random result, although some times I manage to do both holes (vary rarely).
Thanks for your answer


What’s up with the groups? There’s no part of what you’re doing that requires a group at all, and they seem to be complicating a simple matter.

It’s hard to guess what your problem is. Perhaps if you upload the model we can spot the difficulty.


Edit: Two more things: First, if the cylinders are small, say less than an inch or a couple of centimeters in diameter, you’re going to run into problems. Second, with regard to random behavior, as between a computer program and a human being, which one do you think is more likely to behave seemingly at random?

Oh, and:

That sounds like a total of three cylinders, not two as your subject implies.


So I don’t need to group the objects, just select them together. I’ll try, thanks


Something like this perhaps.


iIs there a minimum size for the cilinders?


Due to rounding off errors for small dimensions make the things big and reduce (scale) them afterwards.