Herein I aim to list what I did and learnt whilst building it from conception to completion. I used a couple basic pointers from this Instructable on Leatherworking, but the majority of this was experimentation.
Conception
The first thing I did before anything else was sketch out the basic design and dimensions of what I was aiming to create. Historically, seaxes varied in shape and construction but one of the most commonly related factors among them was that these single-edged blades were kept horizontally inside a scabbard with the edge facing upwards. As I was looking to do something similar and this proved to be beneficial since the construction of the foam seax meant the back of the blade was the thickest part, which made it easier to shape a piece of leather around it with the edge facing the seam and suspend it from a belt rather than the other way around.
I had a pair of snaps on swivel hooks from a couple old wallet chains sitting around (because I hang on to 'useless' junk like that) and decided they would make excellent straps for attaching the sheath to a belt. Not exactly period but hey, this is for a fantasy LARP so to Hel with exact authenticity. They make the sheath a bit more modular without having to undo ones' belt to add/remove the scabbard. I can also attach each snaps to each other if I ever need I larger mount. Also my reasoning for placing the slightly shorter strap near the throat of the sheath was to give it a tiny upturn to the hilt-side of the blade.
Mock-Up
Now that I had my basic blueprint, the first thing I did was construct a mock-up sheath out of cardboard. I actually did this twice, as I realized the first one I made was going to be too tight for the rivets and lining I was planning to add (also I redesigned the point); I adjusted my plans accordingly and made another mock-up with the correct dimensions. I also used a bunch of binder clips instead of staples to close the mock-up and simulate the rivets; I used them to figure out their general placement along with the eyelet straps, and tested the balance of the whole piece by wearing it around.
Cuttin' Time
This was a vital part for me, I had to make sure my pattern was correct else I'd be wasting precious leather. I took my mock-up, unfolded it, and placed it upon my vegetable-tanned leather, where I then traced its outline upon it and then cut the piece from the leather. I then wrapped the piece around the blade and clipped it up, again testing its arraignment.
Because the inside of the leather would be too abrasive on foam dagger and might rub the paint off the blade, I measured a piece of felt the length and circumference of the blade for a protective lining.
Making Impressions
I wanted to try my hand at making actual designs on the leather, as so far it looked a little plain. The difficulty arose lacking the specific tools to carve and 'tool' (leave impressions on a moist surface); also since the local leather supplier had closed I was unsure where I could acquire these tools; so I made do with the (somewhat unorthodox) items what I had available.I didn't have any transfer paper to move the vector images I had selected onto the surface, and I didn't trust plain paper to hold up to the stress of being drawn upon with a stylus against wet leather. Rooting through my junk I found a bunch of printable labels, so I experimented with both the sticky label and the non-stick back by printing the appropriately scaled images on both sides.
Using a damp sponge, I moistened the leather so it'd take an impression better. Using a pointed wooden stylus (normally used for sculpture) I traced the lines of each of the printed images through the template onto the surface of the leather. Both the label (serpent) and it's non-stick, water-resistant backing (raven) worked fairly well for their purposes; though the label held fast enough to the damp surface to get a reasonably accurate transfer without slipping, I was initially concerned that when I peeled the label off of the moist leather it raised some of the surface along with it (noticeable in the top-right photo), but fortunately that has since disappeared.
The basic imprints looked okay, but since I lacked a swivel knife to carve a deeper impression, I opted to use a solid-point burning tool to make the images stand out more. Following the impression lines was fairly easy and the results look great.
Painting
Now, many people dye their leather; I, instead, opted to paint mine using acrylic paint. A couple of the reasons for this are a) I don't know how to confidently dye leather, and b) the Missus used just paint on the leather helmet she built for me and it looks awesome. Any future marks to the leather can easily be touched up with a bit of paint. After the paint dried I gave it a quick layer of boot polish.Then I stitched a small strip of rabbit fur to the end of the felt liner facing the mouth of the sheath (partially to provide additional tension on the blade, as a wipe, and for looks) and glued the whole thing to the inside of the sheath.
I ran into a bit of a challenge as the glue we opted to use was a wood glue that was too liquid-y and seeped through the felt and into the leather before it had time to dry. I then used ordinary white glue, which better suited my purposes.
Hammer Time
Once everything was dry, it was time to punch holes for the eyelets, rivets, and the stitches. We have/had a proper leather punch somewhere, but I was unable to find it where I last recalled it being. Instead I used a hollow length of thin copper pipe with a partially conical end; it worked perfectly for punching the eyelet and rivet holes. I placed the rivet holes relatively evenly across the spine of the sheath approx. every 2 inches, and placed the eyelets between them about 6 inches apart.Stitchin' Time
I used a proper stitching awl for puncturing holes. I knocked numerous holes into and stitched together the sheath point with a thicker buttonhole thread that I waxed prior by drawing it through a lump of beeswax (to improve weather resistance and prevent the thread from drying out and cracking). I worked along the seams one way making a 'Z' pattern, then went in the opposite direction with an 'S' weave.Once I had both sides of the sheath's point sewn up, I did a similar process along the spine towards the throat. I didn't place the stitch holes as frequently as I did on the point (thank the gods); about every centimetre. I kept the rivets in loosely, to ensure the binding didn't offset the punched holes.
I may have made a mistake because when I reached the throat at the opposite end, as I went and fully hammered in the rivets; doing so might've made my attempt to back-stitch down the spine extremely difficult (I broke a needle and my patience in the process). Even when punched, sewing hard leather is arduous for the uninitiated/those without the proper tools. Probably would've been far easier with an actual sewing awl. Plus my stitch holes weren't lined up as parallel as they should've been.
I am unsure if the rivets were to blame and/or if the initial stitching itself combined with poor hole placement made the whole thing too taut to do my back-stitch. I feel the final result might've looked more complete, but with the current mixture of rivet and stitch, I have no concerns about the overall sturdiness of the sheath.
Finishing Touches
I hooked the two swivel straps through the eyelets, and bent them closed. Finally, I gave the whole thing another coat of shoe polish and then blasted it with a heat gun to really bring out the shine.Overall I'm quite happy with the end result, though I have a minor gripe beyond the incomplete back-stitch: I found the white interface backing of the rabbit fur around the throat far too noticeable when viewed up close; it looks better now that I've painted it a darker shade but I would've rather if I didn't have to do that in the first place.
I've worn the sheath during rather vigorous activity and it performs admirably; it's tight enough the blade doesn't slip or fall out, but not too tight as to make it difficult to draw. All-in-all this was a good project that improved my confidence, know-how, and skills when working with leather.