Time to drill/shape the square hole in the F-757 gusset. I have been marking parts like this with my caliper. It makes a straight precision location scratch mark. Then I go back and draw a black sharpie line on top of the scratch mark.
As you can see in image 1, I started by drilling ¼” holes in the corners. I used the drill press but did not clamp down the gusset. Used a small dermal tool cutoff wheel to cut out the center.
I finished the corners with a small file as seen in image 2.
Image 3 shows finishing off the straight edges with a sanding stick. I have this new idea to make sanding sticks. I affix sandpaper to a scrap piece of aluminum with double sided stick tape. Works good.
