How far do I need to cut to get to good metal to weld?

You guys are awesome!

As an old man who's never done this before I really appropriate you folks taking the time to teach.

Since I have worked on helicopters and airplanes most of my life I am familiar with my metal guys repairing drama g e around the world. I am fortunate enough to have a few hundred Clekos and have come knowledge of how to use them.

I purchased eight of the clamps shown above by Tooljunkie from Eastwood. I am sure in other places they will be useful. The Brass idea is killer as I have a whole lot of trim holes to be filled.