As I am a lazy engineer I am always looking for the quickest way to get to the end result. So, when machining a radius in the lathe I use corner radius milling cutter. This saves time and a lot of time grinding high speed steel (HSS) They can also be used to create both internal and external radius. The cutting edge also gives a good finish. When I go to tool sales auctions I look for damaged radius cutter as they are worth buying as they will be cheap, you can also point out to the seller it is damaged so a cheap deal can be struck. As there are normally four cutting edges on a corner radius cutter and as long as the tool has one good edge you can use them in the lathe.
Again, not a homemade tool but hopefully helpful to some
Thank you again for viewing
The Home Engineer