Look at me using X-Carve as a verb. Just set up the machine with Easel to the thickness of your material, I used ~1/8" thick ebony. Go slow with the 1/8" bit flute bit. The hardest wood on Easel is bubinga, ebony is ~25% harder than bubinga (14in/min or less). The depth should be shallow as well, I found ebony’s irregular grain make it want to chip, I went no deeper than 0.01"/pass. It takes awhile to carve, but not like you have to sit there and watch the whole time, unless you get hypnotized by the X-Carve like I was. Once the blank is cut out just chop it loose with a chisel. (Caution, the dust from ebony can be an irritant to some people.)
The leather is a bit trickier to setup on the X-Carve. I used 8-10oz vegetable tanned leather, this means the thickness is about 1/4"; though the thickness will vary slightly for any given piece of leather. The photo shows how the X-Carve did not cut though the leather at every spot. This is due to two reasons. First, it is difficult to get the leather to lay flat; second is the inconsistency of leather. Also the leather should be cut from the suede side. I did try cut the leather using the 1/8" flute bit from the top grain side, it tore up the grain. The bit is the same one as the ebony. Leather is easy for the X-Carve, use the acrylic setting on Easel (or more aggressive).
The blank needs to be shaped so that it can actually open paper (or plastic) envelops or Pony Express Mail. I used a file to do most of the shaping. Ebony is a very strong wood, so a thin piece can slice open letters, sharpen the edge to the consistency of a butter knife, that is plenty sharp. The center should be about ~1/8", a little less won’t hurt a thing.
When shaping the point, I braced the ebony against my finger because I felt it flexing with the file. Finally, shape with 100-180 grit sand paper, and finish it with ~220 grit sand paper.
Cut the leather pieces out using scissors, a knife, or a chisel like I did in the photo.
Use the tabs on the leather handle pieces as a guide; use epoxy to glue the leather handle pieces to the ebony. Don’t worry about the rough edges on the leather pieces at this time, we’ll take care of that in the trimming. Let the epoxy cure o/n, then trim all the edges.
I made a design change from the original here but cutting the corners off the letter opener’s handle with a coping saw, but any hack saw can do the job. I dyed the edges with red leather dye.
Let’s mark the position of the ebony on the suede side of the leather, then carve out the center with a gouge. Since the position of this groove is not critical it can be made by throwing it back onto the X-Carve (probably should do that before cutting it out). The space should bind the ebony, but not so tight that you could poke an eye out trying to pull the ebony out of the sheath.
Mark the spacing for stitching, you can substitute a stitch marker with a fork. Use the tabs to align the sheath parts, and secure the sheath pieces with a few single stitches.
Stitch the sheath. I used 4 cord waxed flax seed, but any waxed thread will do. Stitching can be hard on the hand and patience, so any method of securing the sheath together is fine (rivets, wire). You may need to glue if you decide to pass on stitching.
Once you are finished secure the two sheath pieces trim the tabs and the edge with a chisel. The dye the pieces the same color as the handle.
The leather edges should be fairly stiff after the dye dries. Take advantage of this by rubbing some wax on to the edge, I used beeswax, but any wax will do (no don’t use ear wax, if you can find ear wax in that quantity, then you might have a problem.) Use a hot iron to press the wax into the edge of the leather.
The iron should be ~160-180 degrees F (about the melting temperature of beeswax). If you don’t have a edge iron like I have picture you can do a situation substitution: An iron poker, a small hammer, a bar of metal, the bottom of a pan, etc.
Trim the edges, it’s not a necessary step, the tool is specialized. Your letter opener should look pretty good even without trimming. But trimming does add to the overall look of the project, if you want to sell this project, I suggest trimming, following by a good burnishing.
The last step is to apply a coat of Neatsfoot oil (wait o/n) on the leather parts then apply a coat of shellac (wait o/n) on everything. Shellac is great for wood and leather. Voila!