Editing STL file of a wheel - making outer diameter bigger while keep the center hole the same size

[jimsujimsu]

I have a STL file of a propulsion wheel for a tennis ball training machine.    It converts a tennis ball machine to a pickleball machine.  The design is for a different machine and for my machine it needs to be bigger.  There is a center hole for a screw to secure the wheel which currently fits perfectly.  I was able to make the wheel bigger, from the current 118.36mm to 138.36mm, but it changes the entire unit so it also changes the size of the hole in the center. 

How do I make the outer diameter bigger without modifying the size of the hole in the center.  I am guessing I need to split the single unit into parts but I am a beginner on 3D design and printing so need help on this.

[laughingcreek · Accepted solution]

I would only rely on the stl for a visual reference.  model it natively in fusion then make adjustments from there.  attached is a good start.  edit the dims in the sketches to get to where you want.

[jimsujimsu]

Thank you so much!  This helps quite a bit with the different sections separated.  Would you mind letting me know if you did that through Fusion or another program and what is that function or procedure called to separate the sections.  That way I can look into how to do that in the future.  Thanks again!

[laughingcreek]

my model was done completely in fusion.  I don't know what you mean by dividing it in sections.  i sketched it from scratch and started using the solid modeling tools that made sense for the geometry.

I suggest stepping thru the timeline a few times to see how each step was done.  ask questions about the steps you don't understand.

[jimsujimsu]

Understood and that is impressive. I didn't think that you had made it
from scratch and thought you had edited the original file. Thank you
again.

[etfrench · Accepted solution]

You can also use the Mesh tools to add on to an existing mesh.  Once you have the section sketch, you can either use it to add on or use it to create a new native Fusion model with relatively accurate measurements. 

For something this simple, it would be best to just model it like @laughingcreek shows😁