I was playing around with my new welder, and eventually, I did this. That is a 3/16" round attached to a 1/4" flat - a very common joint for a truss rod. It's not beautiful, but it is strong, you can see how I tried to pull it apart. Then I sawed the end off, and you can see it is solid - no slag inclusions, just two pinpricks at the 'corners' of the round. Welding is not as scary as I thought, but it is going to take a lot of practice. My welds seem to be a matter of luck, but my luck is improving.