To hold the centerline on the workpiece will help the device shown in the figure.
Recommend to read
PETAL COPIER
To get a perfectly accurate joint of the flat parts with a curved surface allows simple reception. Take a sheet of thick paper, such as Whatman; one edge cut into a narrow strip and...
WELD DC
Advantages of welding machines DC before they "perimentally brothers" is well known. It's mild arc, and the ability to connect thin-walled parts, and less spatter, and the lack of...