Gap for brazing thin casting? Non-automotive
Took a while to get all the patches in the wall and pieces test fitted.
When the paint is dry I'll put the working register in. and then the grill. But this is a test fit with a spare grill.

Still working on a copying the control rod threads for the register that allows heat to go up the flew. Need it for a similar second floor control.
Looks like 24 threads per inch but its a rounded thread form.