Scratches in Aluminum Wing Brackets

[birdus]

I'm about to finish my first set of aluminum wing brackets for my Super Baby Great Lakes. To clean up some of the marks which got onto the bracket while working, I placed a piece of 320 grit sandpaper on my table saw (cast iron table) and ran the piece over it with some vigor. That cleaned it up quite nicely. I had also run a piece of 220 grit around the edges by hand just before this. The piece feels completely smooth to the touch, both around the perimeter and on both sides. However, one can see scratches all over the piece from all the sanding. I'm guessing the scratches are all small enough that primer/paint will make them invisible, although I don't know that with certainty.

My question is how small do the scratches need to be so as not to be a concern for stress risers?

Thanks,
Jay

 

[Matt G.]

 

[birdus]

 

[TJay]