>>1804028I think you're over thinking this. It's just filing a bump off of a flat piece of metal.
Stabilize the fork sideways so the lips are failing straight up. Clamp it to a table with one leg going under the table, one leg on top (like the fork is straddling the tabletop. A countertop would work here too)
Made this picture, black is table, red is fork, green is the lips. But really this is just how I'd do this. There's a million ways and you probably can do it wothout clamps
Then just get your big flat file and take long even strokes. I think it won't take you as long to do it by hand as you think it will. Metal files are pretty quick on small work like this.
