Cupid Bows, in zillions of variations, are a common decoration on mitre planes (see the works of Bill Carter and Daed Toolworks for some of those variations). The basic shape is pretty simple but it took me a while to figure it out so I thought I’d write it up. I present two forms: square and champfered.
Get a piece of metal the correct width (I like to leave it long so I can grip it in the vise and have room to file). Using a triangular file, notch the center and two spots about a third (measured to the center) of the way in from the edge. Using round files, enlarge the edge notches (this plate is 1″ wide, the final file is a skinny 1/2″).
Using a knife file and elliptical needle file, add a “beak”. Be careful with the knife file, it jams in the slot and is really easy to break. I think a hacksaw would also work here.
File down the middle nubs, this gives bow a more bow like shape. Then round over the nubs (I use s square files and triangular needle files (all with safe edges, which is important as I use the safe edge as a steady rest). If this is a square bow, your done.
Now add the champfer. I try to make it so it is level (when installed), the longer the champfer, the more dramatic it is. I also taper the champfer. I use the safe edge files mentioned above plus a rat tail file. I try to keep the champfer flat.
Last is the not so fun part, polish. Clean as much as possible with fine files, then sand (I start at 120 and go to 400). Rounding over the leading edges on the face (with sand paper) seems to add a nice effect. I do this by sanding side to side with my finger as the pressure pad. That is good for a matte finish, otherwise, off to the buffer with the green crayon.