Attach your file, but you must fix something, like tjhe gap between the wheel and the axe and merge the bodies I think
I'd click on the face of the cylinder that's tangent to the disc and choose "Extruded Boss/Base". That will open a sketch on the face, and the face will still be highlighted. Choose the sketch tool "Convert Entities", which will place a circle coradial with the outside of the cylinder face. Close the sketch, and choose "Up To Body", select the disc, and make sure the "Merge result" box is checked.
You can only added fillets to one solid body per. fillet feature. So edit the cylinder feature (extend its length) to 'intersect' the intended body and select 'Merge results', then add desired fillet.
Keep in mind, Merge results default is to merge all bodies (that intersect), so if you have a body you don't want it merge with the other bodies, you have to change feature scope to 'Selected bodies'
Thanks this helped a lot.
extend the cylinder into the hub-
combine the two required bodies- your tree shows 4 bodies atm
fillet or edit as desired
there's some good tips in the SW tutorials
hope this helps - have a good'n -