I have a hollow rod that is too large for my humble printer to handle. I am also very much a novice when it comes to using 3D modelling software and CAD. I was wondering if anyone has any advice, tips, tutorials on how to go about tackling this challenge.

I have attached a screen capture of the part itself, which I got from Thingiverse. The 2 halves of the rod needs to be securely connected as it is a hub for other pieces. The outside diameter of the rod must also remain intact. On the other hand inner core of the rod could be made solid, or a portion of it for something like threading.

The object itself is part of a math spinner that I am building for my daughter.

Any assistance is greatly appreciated.
core_rod.jpg