For anyone new to cad I recommend trying to learn exactly as you'd machine a part... unless you can't machine what you want to make because it is print in place 3d print or something.
Start with a form and remove material... when needed create sketches on faces to execute material removal. Learn how to create offset cutting planes, or 3d cutting tools, and to split bodies and planes.
Then learn to create splines
Quick Tip:
Need to model and 3D print a part fast and don't have reference dimensions, can't find a step or stl file of the part?
Cheat...
I needed to reuse the knock-out holes in the electrical cabinet of my lathe. But I needed to insert the much smaller PG7 wire glands I needed to use than the 3/4" hole. This is the PG7 glands I have without the retainer nut in place.
I couldn't find my stash of reducing spacers anywhere and a search of thingiverse turned up nothing.
When I turned to modeling spacers I thought it would be much more secure to make a spacer that the PG7 would screw directly into. I also wanted to use a solid screwed connection that filled the 3/4 hole for better security. I thought what I really need is a PG7 and PG13.5 combination piece.
But Fusion lacks the thread presets for DIN PG connector threads and I didn't want to go thru the effort to add them. So how to quickly model this combo piece?
Use the parts bodies and cutting tools that are readily available from mcmaster carr. Here is how I made this part:
I created a new component called adapter.
I selected insert mcmaster carr component and searched PG13.5 wire gland. I downloaded the step file and hit ok to insert into the fusion file.
Next I went to the component bodies and hid all the bodies except the main core of the PG13.5 as below.
Next I created an offset plane along the line I wanted to sever this part in two. Then selected modify "split body" selected the core and then the construction plane as the splitting tool. This is the result (after I selected the cast off portion of the body and hit "remove"
So now I had the portion that goes into the 3/4" hole in the electrical cabinet. But I needed to add threads to screw the PG7 into. How to get those when the thread tool doesn't have the correct threads? Cheat some more.
I went back to insert and downloaded the PG7 part from mcmaster carr.
I selected the PG7 bodies and hid every body except the core body again. I then moved the PG7 core into the unthreaded hole in PG13.5 like this:
Then with PG7 body still selected I hit modify and then scale and entered 1.01 for the scale factor just to create a little more thread clearance when the next step is performed.
Then I selected the PG13.5 body and selected modify and split body. I then selected PG7 as the splitting tool. This cuts the internal threads out of the PG13.5 core.
This leaves the part complete as I want it printed.
Export to cura as per normal and print.
The result:
It took way longer to write this than model the part. it took me literally less than 4 minutes to model this part to match the pg7 wire gland I have and the pg13.5 retaining nut I already have... but I'll model new nuts anyway.
In Mcmaster's models many of these types of parts dont have the thread cut in them so you would just use the same above technique