I get a lot of interesting jobs to do. I've been at it for 40 yrs and maybe that's why. If you have access to air arc carbon, and have the correct size, it will stop weld metal from migrating into holes, (Threads or no threads). Round ceramic backing material works also. Simply place the carbon or ceramic in the hole and weld. I try to stay away from metals like aluminum, brass and copper, because they tend to get stuck in the holes. If the carbon or ceramic gets stuck you can punch them out, and in blind holes you can pulverize them and remove with air.

Dennis