Almost all of the sheaths I make are deep sheaths. That is, they come up the knife handle far enough to hold the knife securely without a keeper strap. The common sheath with a snap-secured keeper strap is a nuisance, and an invitation to lose your knife. Some fifty years ago I lost a good Boy Scout sheath knife, because the keeper strap didn't stay snapped. When I was able to buy another, I made a sheath for it that didn't depend on a strap for retention. I still have that knife. Because there's no snap to fumble with, it's easy to get the knife in and out as needed.
The deep sheaths are also historically accurate, and you'll want this style to complement a traditional knife.
An exception would be very large knives, which border on being short swords. As a rule, these are sufficiently blade-heavy to stay put. Even here, a friction fit is a good idea.
If possible, study original examples from the period that you're representing. I strongly recommend "Knives and Scabbards" from the London Museum for early sheaths, and "The Knife in Homespun America" by Madison Grant for Colonial Period sheaths. The book "Knifemaking" by Bo Bergman has excellent instructions and illustrations for Scandinavian style sheaths. Sadly, this book has gone out of print, but you may be able for find a copy at your library.
You'll start with leather of course. You want tooling leather tanned with Oak bark, rather than the commercial chrome tanned leather. Tooling leather takes up moisture, and becomes soft and easy to work. If you're going to line the sheath with wood (more on that later), the leather can be quite thin. Otherwise try to find fairly stout leather. Pieces from the back of the hide are the most durable. Pieces from the belly are more likely to stretch, and work easily over a wooden core. Tandy's leather craft chain is a convenient source for small quantities. They may cost a little more, but you can buy small quantities, you'll be sure of getting tooling leather.
I get my leather from M. Steffan's Sons, Inc. This is probably the is the oldest leather goods store in the nation under the same name and family. Now operated by the fifth generation, it's a great source for leather and leather working supplies. This is where I get the leather I sell on the web page. You can reach Linda Steffan, the current owner, at 716-852-6771.
I like to sew with linen thread. It costs a little more than the artificial stuff, but it's traditional, and makes a nice appearance. Over long periods of exposure to moisture, it can rot however (like most natural fibers). Artificial sinew is a cheaper, durable alternative.
If you're being very historically accurate, and doing American colonial period, you may want brain tanned leather, and real sinew. If you have ready access to these materials however, you probably don't need this primer.
If you are going to line the sheath with wood, you can use any wood not prone to splitting. Basswood is light in weight and easy to carve. I expect Birch or Willow would be the common woods used for the purpose in Scandinavia. Birch is very durable, but a bit harder to carve. If you're making a wooden sheath, where the wood will show, you want something decorative of course. Curly Birch is the obvious choice for a Scandinavian knife, but figured Maple is often used for early American styles. Try to get a piece with consistent grain, large enough to make the handle and sheath out of the same block for a nice match. There is more on wood sheaths below.
Traditional deep sheaths are form-fit to the knife and sewn up the back. You want it to come up the handle far enough to hold the knife securely. That usually means up over the guard, if there is one, or over the swell of the handle. If the knife has a large guard, or double guard, this style will not work very well.
The sheath is suspended by thongs or straps. You can either sew these into the seam, or add them later. Period sheaths were sometimes made without any way to attach them to the belt. The buyer added straps depending on how it was to be worn. There are illustrations of sheaths worn vertically as we wear them today, but also sometimes at an angle, or horizontally, or attached to a belt pouch, shoved into a boot, hung by a thong around the neck, etc. Most likely you'll wear the sheath vertically, however. If you are making an early style sheath (medieval), or Nordic style sheath, the straps should be long enough for the sheath to swing freely. This allows the sheath to be worn in the front, and move out of the way when you bend over. In Scandinavia, it's also common to wear the knife on the left side, so that the sheath can be grasped by the left hand while the knife is drawn by the right. Alternatively, the sheath is pushed off the knife with the thumb of the right hand, while the knife is held by the last three fingers of the right hand.
If you plan on hanging the sheath by a strap, you can widen the seam toward the top of the sheath, and punch a hole in it as an anchor for the strap. It's common to wind the strap once around the sheath so the weight of the knife tightens the hold of the sheath on the knife.
Lay the knife on the leather at a right angle to an edge, so that the edge comes as far up the handle as you wish the sheath to come. Draw a line around the edge side of the knife, leaving extra for the seam. The amount you have to leave varies with the weight of the leather and the type of stitch you plan to use. About a quarter inch would be a good starting point.
Now roll the knife away from the line so the other side is down. Draw another line as before. If you're going to add extra for a strap hole, do so now. Cut out on the line, and soak in warm water to make the leather soft and pliable. If you are going to tool the leather, the maximum softness of the leather can be achieved by soaking it until it stops releasing bubbles, then wrapping it in a damp towel overnight.
Sew up the seam. There's several ways to do this. The traditional method is to punch holes with an awl (an icepick works fine), then use two needles and a "saddle stitch". To do this, punch the holes for your seam. You can get a hole spacer which looks like a gear on a shaft. You run it over the leather and it makes evenly spaced marks for your holes. If you have a drill press, you may want use it with either an ice pick prod, or a tiny drill. Fold the leather into position when making the holes, so you're sure they will line up. If you have a hole spacer you can do the sides separately, and count the holes so as to have the same number on both sides. Cut a piece of thread long enough for the seam (at least four times the length of the seam). Thread a needle and run it through the first hole. Center the thread so you have equal amounts on each side. Thread a second needle on the other end of the thread. Pass each needle in turn through the next hole and draw tight. When you get to the end, tie it off. The advantage of the saddle stitch is that it does not pull the sheath out of shape as an overhand stitch would. It also gives a much neater appearance. After stitching, trim the edges of the leather for a neat appearance.
Traditional leather workers use a “clam” or wooden vice to hold the leather being stitched to ensure the layers don’t shift during the process. This is helpful, but not absolutely necessary as long as you are careful to keep your holes properly lined up. Here’s a tutorial on the saddle stitch.
You can buy stitching awls ("Speedy Stitch", and others) that produce a lock stich like a sewing machine, and are supposed to make this easier. I have had very poor results with them. It's difficult to keep the holes straight, so the back of your seam is irregular. Unless you are very careful, the lock stitch becomes pulled to one side and betrays your non-period methods. Also the resulting seam is not as strong. In addition, I find them to be more work than doing it properly in the first place.
After the seam is stitched, mold the sheath to your knife. Wrap your knife in cellophane to protect the blade from the wet leather and provide additional space around the blade in the sheath. Re-wet the sheath. Work the sheath over the knife with the seam centered in the back. When it's all the way in, mold it to the knife with your fingers, or a smooth hard object such as the handle of a table knife. When you have it the way you want it, set it aside in a warm place for a day or two, with the knife still in it.
The leather will shrink a bit as it dries. But the layers of cellophane will help provide a bit of clearance and slide against each other so you can remove it the first time. Most knives used with deep sheaths do not have a finger guard. If your knife does have a pronounced guard you may have to use a spacer behind the guard while molding the sheath. Just cut a block of wood and wrap it with the handle in the cellophane. If you don't do this the leather will shrink to fit behind the guard and you won't be able to draw the knife.
When it's completely dry, it will be quite stiff. You need to seal it from becoming wet again, so it doesn't lose its shape. I like to use a mixture of wax and beeswax. I don't find the exact ratio of beeswax to paraffin wax to be critical. I've varied it from about half and half to mostly paraffin wax. The more paraffin wax in the mix the stiffer the sheath will be, but the difference isn't dramatic. Carefully melt the wax in a shallow pan long enough to hold the sheath. Bread pans work well. It's safest to to do this in a double boiler arrangement. If you use direct heat you might want to do it outside in case it flares up. At the very least, be sure you have a suitable lid to smother it if necessary. Do not leave it unattended while it's heating! Just after all the wax melts it should be warm enough. If it is too hot it will shrivel and damage the leather quickly. If it is too cool the wax won't penetrate evenly. Briefly dip the sheath into the melted wax mixture. It helps to have a piece of bent wire (coat hanger stock works fine) to manipulate the sheath. Watch the surface of the leather. As it takes up the wax it will darken. As soon as it is evenly darkened take it out. If you leave it too long it will shrink and distort. When it cools, it will be hard, durable, and waterproof. If the color is uneven, or if you have lumps of wax on the sheath you may want to use a hair dryer to melt the surface and wipe it down. If you don't want it to be quite so hard, add more beeswax, commercial waterproofing, or even neatsfoot oil to the mix.
Don't put the knife into the sheath until it's cool. If you put it in too soon the hardening wax will bond to the handle, and it will be almost impossible to get it out. (Do you hear the voice of experience here?) After waxing, the sheath will have a rich dark brown color. Waxed sheaths can be very durable. I have several that have been in use for many years.
You may wish to use a wood liner. This will protect the leather from the sharp blade and make the sheath more durable. It was a common practice in historical times, and is still often used for quality custom knives. Using a liner allows you to use a thinner grade of leather. Thinner leather is easier to work, so it partially offsets the extra work of making the liner.
Take a block of suitable wood and lay the knife blade flat along the grain with the end of the block at the handle. I like to work with basswood. It's easy to carve and has little tendency to split. White Pine, or Sugar Pine are easier to find, and work easily, but sometimes have more tendency to split. In Scandinavia Birch or Willow would probably have been common. Birch is very durable, but harder and a bit more difficult to carve. Trace the shape of the blade on the block. Carve out the trace until the blade fits below the surface. Then carve the sides and back, but leave a flair at the handle (top) end, so the wood of the liner transitions to the handle smoothly. Open the inside at the top in a funnel fashion to guide the knife in. Round the corners and smooth. You may want to make a top panel to completely enclose the blade. If so, glue the open side to a flat piece of matching wood, and shape to match the bottom. The top panel is left flat in the inside, so the join is not in the center. Period wood lined sheaths were made both with, and without, the enclosing panel. After making the wood liner, assemble as above, measuring the leather with the liner in place of course.
When building the one-piece liner, it seems logical to face the open side up, away from your leg. However most Nordic sheaths I've seen place the open side down, on the seam side, toward the leg. This allows the seam to fit into the opening and makes a neater job. If you're completely enclosing the blade, you may wish to carve a grove on the back of the liner for the seam.
While the liner seems like extra work, it allows you to use much thinner leather, which is easier to cut, sew, and shape. In the end it works out about even.
If you're using thick leather, you can make a neater job by using a butt stitch rather than a saddle stitch. In this stitch the edges of the leather butt up square. You use a criss-cross pattern, exactly as you tie your shoes, to draw them together. You do not have to allow as much for the seam when cutting the leather for this method. If you wish have a tab for a suspension strap anchor, you can transition to the saddle stitch near the top. A disadvantage of the butt stitch is that the threads are more exposed to wear. You can minimize this by pressing them into the softened leather before it dries.
Since you're using tooling leather, you could tool it. Borders, runic inscriptions, and stamped patterns are all suitable for various periods. Again, try to study some period examples if you can.
These are easier to make, but use more leather. Simply fold the leather over the knife, and leave a one to three inch border. Again, the sheath comes far enough up the handle to secure the knife. Stitch twice, once around the knife to form the sheath, and once around the edges. This leaves a lot of surface to decorate. You can use a stiffer grade of leather for this style. I've even seen some Viking period sheaths in this style made of sheet brass, elaborately decorated. A variation uses sheet brass on the skirt and at the throat. In the late American fur trade era, this style was commonly used with a wide slot cut in the border for the belt or sash. These were often fastened and decorated with brass tacks rather than stitching.
Wooden sheaths were quite common for swords, saexes and larger knives. The sheath usually encloses only the blade. It can be lined with felt or lambs wool for a friction fit. This style can be very striking. You can decorate with carving, wire inlay, tacks, or even jewels. The early versions had elaborate fittings of bronze, often gilded. Since a large sheath is a highly visible item of attire, in some periods it received as much attention and care as the contents.
Wood sheaths are made more or less the same as the wood liner, but using a quality hardwood. Try to match the sheath and handle woods. On better grades metal fittings are fabricated for the throat, tip, and suspension.
A variation is to make a visible wood sheath for the blade portion, and add a leather upper section for the handle. This is done in Northern Scandinavia by the Sami peoples. They may also use bone or horn rather than wood for the lower portion. The traditional join is accomplished by carving protruding ears at the top of the wooden portion to engage cutouts in the leather upper. The leather part is stitched up the back as above.
This is a non-traditional sheath. It's the pattern I worked out when I was a boy. It's very simple to make, and economical of leather. It is, I think, rather elegant. I've seen others like it in later years, which I'm sure, were developed independently.
Lay the knife on the leather; handle toward you, edge to the right (for
right handed). Draw around the edge, leaving a margin for the seam as before.
Draw a line perpendicular to the knife where you want the top of the sheath.
Roll the knife as before, and draw the other side. Draw an additional tab on
the top, which will fold down and form a belt loop. You want this centered
on the knife, and it should not extend to the edge of the sheath or you won't
be able to wrap the leather around the handle. It should be long enough to
fold down to the area of the blade. It will fold from the top of the sheath,
and the top of the sheath will ride level with the top of your belt.
Cut out the sheath and wet it as before. First fold the belt loop down and
stitch or rivet it in place. Do it right, because after you stitch up the
side, you won't be able to get at it again. Fold over the sheath and stitch
up the side. Mold it around the sheath as before. You may want to place a
single rivet in the side to act as a stop for the guard, and keep the edge
away from the stitching. You can also welt the seam. That is, insert a layer
of leather in the seam before stitching. You could of course line these with
wood also.
Because this pattern holds the knife tightly to the belt, you must wear it to the side or rear. If you wear it to the front, the knife could hurt you if you trip and fall.
Since writing this I've come upon Bo Bergman's book on knifemaking. The sections on sheath making are excellent. I wish I'd had the book when I was fumbling my way toward workable patterns and methods. I highly recommend the book to anyone interested in sheathmaking. It's now out of print, but should be available from local libraries or used book dealers.
I had intended to add photos of the process, but recently I've found there are so many excellent tutorials on the 'net it would be redundant. I still will if I get around to it. .