Ok, my inexperience is going to be very apparent here, both in not knowing how to do this and not really knowing for sure how to ask! I have a rectangular 1"x1-1/2" hole milled all the way through a 2" block (4140) and I need to clean up the corners. I have the hole milled to size but the corners have a 1/4" radius (?) because of finishing with a 1/4" end mill. How do I finish these corners?

The fit is not critical here (a part for a plow) and I could finish it with a file but I am trying to get it as perfect as possible because I need to learn how for future projects. How would I approach this if it was indeed to be a precision part with both fit and appearance being critical?

The fit is not critical here (a part for a plow) and I could finish it with a file but I am trying to get it as perfect as possible because I need to learn how for future projects. How would I approach this if it was indeed to be a precision part with both fit and appearance being critical?

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