A hand-crank machine splitting a strip of bridle leather on a wooden workbench.
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Skiving and Splitting: Thinning Bridle Leather Without Weakening It

ByPeter Joeseph 'Briefcase Maker' Kalafatis

Every shaving that comes off the leather was holding something.

Skiving and splitting both make bridle leather thinner, and both take strength with them on the way out, which is the part nobody prints on the box. I split and skive strips on an old-school hand-crank Weaver machine. I have skived bridle loops for a briefcase flap pivot bar and split an English bridle strap. Nobody gets to thin leather for free. The only real question is where on the case you can afford to pay.

Video: Splitting / Skiving Leather Strip With An Old School Hand Crank Weaver Machine, from Marcellino NY Briefcase Maker on YouTube.

Two cuts that get confused

One thins an edge. The other thins the whole piece.

Hands skiving the end of a bridle leather loop with a knife on a glass surface.

A woodworker would see it in a second. Plane the face of a board and the whole board gets thinner. Chamfer an edge and the board stays as it was, with only the corner eased off. Leather has the same two moves, and people swap the names all the time.

The Leather Dictionary’s entry on skiving draws the line clean. Skiving thins the edges of a piece to a set thickness, tapering toward the border, and leaves the rest of the piece alone. It gives the reasons: an edge that has to fold, a part that has to join another, the overlap where two strap ends meet and need more surface for the bond. Splitting is the other move. The conservation glossary hosted by Conservation OnLine defines it as dividing leather horizontally into layers, and says tanneries today do it with a high-speed endless band knife and rollers that set how deep the cut runs below the grain.

At my bench, splitting means feeding a strip through the crank machine so the whole length comes out at one thickness. Skiving, the way most makers use the word, means a knife or a skiving machine taking a taper off the last inch or two.

SkivingSplitting
What changesEdges or ends, taperedThe whole piece, to one thickness
Typical toolsSkiving knife, safety beveler, paring knife, skiving machineHand-crank or powered splitter, tannery band knife
Where it helpsFolds, turned edges, overlaps, strap endsStraps and loops that must be thinner along their full length
What it costsStrength at the tapered part onlyStrength along the entire strip

The table makes it look tidy. The leather never read the table.

What the split takes away

The strength sits in the middle of the hide, and splitting cuts through it.

Here is the fact that should stop your hand on the crank. The CoOL entry says it straight: “Splitting always causes a loss of strength per unit width,” and the two layers together come out weaker than the leather was before the cut. It puts nearly all of leather’s strength in the corium, the fibrous middle layer, not in the grain on top.

Its numbers are for vegetable-tanned calfskin, not bridle, so they carry over only as a warning. For that calf, the grain split kept between 3.5 and 12 percent of the original breaking strength, while the flesh split held roughly 54 to 70. The grain is the pretty side. It is not the side doing the lifting.

English leathermaker Tusting lays out the layers its own way: tightly knit fibers at the grain, a looser and messier middle, a tighter weave again at the flesh. Its point is that a split layer without the grain is far less resilient and can tear easily, and that full-grain leather keeps its tear strength even when thinned a great deal. Both can be true at once. Full grain split thin is still stronger than a split pretending to be full grain. It is weaker than the same full grain left thick.

A leatherworker.net thread on grain versus flesh strength shows how unsettled this gets once it hits the bench. One poster cites a 1926 study that found splitting always weakens leather. Another points out the study tested one area of one kind of hide and never pulled anything to breaking. Nobody in the thread claims to know exactly how much a given bridle strap loses, and that kind of honesty is worth more to me than a confident rule.

The hand-crank splitter

A splitter is only as even as its blade and its rollers.

Cross-section of bridle leather showing full thickness next to a skived taper.

The machine is simple to describe. Weaver Leather Supply sells a Master Tool hand-crank splitter with an 8-inch hollow-ground blade, roller bearings, and a lever that adjusts for leather from 3 to 14 ounces. It bolts to a bench and weighs about 87 pounds boxed.

Easy to describe. Harder to run. In a thread on setting up a crank splitter, one owner reports getting the blade sharp and still finding that test cuts came out either paper thin or barely shaved, with nothing usable in between. Weaver’s own product page carries a customer review complaining of uneven splits on 8-ounce leather. Neither is a reason to skip the machine. Both are reasons to run scrap first, every time the blade or the setting moves.

My opinion: bridle makes all of this harder. I call it waxy, thick, heavy and stiff on my Leather Choices page, and my view is that a stiff, waxy strip leaves a splitter less room for error than a soft one does. A strap that feeds unevenly comes out with a thin spot, and a thin spot in a strap is where it stretches first.

A crank machine is slow. In my opinion that is no drawback when the strip coming out the far side has to hold up a briefcase full of files, every working day, for years.

One reason I split a strap is to put it back together. Two thinned pieces, flesh to flesh, stitched into one strap with a good grain face on both sides. It sounds like going the long way around the block to reach the house next door, and it is, but the strap looks finished whichever side ends up against the coat.

Skiving by hand and by machine

Thin, sweeping passes with a sharp blade, and scrap before the real part.

Most of the thinning on a briefcase is skiving, because most of the trouble lives at the ends: a loop that wraps a bar, a strap end that doubles back, an edge that has to turn. Jeff Peachey, a book conservator and toolmaker, has written about paring leather with more care than anyone else I read on the subject. In an overview of paring tools he notes that English-style knives with a straight, angled blade are easy to learn and suit edge paring, while rounded French-style knives can thin larger areas but are harder to control.

His longer guide to paring leather says to build the taper with a run of cuts at lower and lower blade angles instead of one hard pass. “As the leather becomes thinner, it becomes weaker,” he writes. So he changes his grip and his pressure for the later cuts, and when the work goes wrong, the first thing he suspects is a knife that is not sharp enough. Stray crumbs of leather under the workpiece, he warns, can push the blade through and cut a hole.

He works mostly with thin bookbinding skins, not heavy bridle, so his methods carry over to my kind of work as principles, not recipes. In a leatherworker.net thread on skiving evenly, one maker using a safety beveler reports stropping it every five to ten cuts, working on glass or marble, beveling the outer edge first and then taking the interior down in thin passes no deeper than that edge. Another poster suggests sending large areas to a saddle or shoe shop with a machine.

The bench test is the same either way. Run the taper on an offcut of the same leather first.

How much to leave

Thin where it folds. Full thickness where it pulls.

A skived bridle leather loop stitched around a brass pivot bar beside test strips.

Here the woodworker earns his keep. Plane a board too thin where a hinge screws in and the screws pull out. Leather fails the same way, right where the load meets the thinned part.

Some thinning is part of the design. My gussets run thinner than my panels so the case bends at the sides without creasing across the face. That is a whole part split down on purpose, and it works because a gusset folds and does not carry the handle.

For strap ends, a leatherworker.net thread on skiving strap ends lays out the two camps. Some makers skive only the very tip so the folded section stays full thickness. Others thin the whole fold. The maker who answered takes off about a third of the thickness over the whole fold area, and gave the example of skiving about three inches where a buckle tine passes through at an inch and a half, so the snaps, keeper and buckle sit on full-thickness leather. The original poster agreed that the same rough fraction suits bag shoulder straps. That is one craftsman’s rule, reported as his. It is not a standard, and no source I fetched gave a universal number.

My opinion, as a maker: the safe places to thin on a briefcase are the ones that fold or overlap and carry little load on their own, such as a turned edge or the tail of a loop stitched flat. The place I would not thin is the stitched join that carries the handle or the strap. That join is where the saddle stitch does its work, and a stitch can only hold as much leather as is left around it.

Also my opinion: a briefcase that gets carried hard has to be thick leather. Thin leather built up with cardboard filler breaks down once moisture gets into it, and thin cases with big price tags can come apart under heavy use well before anyone expected. Skin and paper. Paper loses.

Where the argument breaks down

Full-thickness bridle refuses to fold neatly, and sometimes that costs more.

The case against thinning has a soft spot, and skipping it would be cheating. In my view, full-thickness bridle wrapped around a pivot bar will not lie down. It bunches. A strap end doubled back at full thickness can get so fat that a keeper fights to pass over it, and that bulk leans on the stitch line every day the case gets carried. Bulk breaks things too. It just takes longer about it.

Weaver’s guide to hide cuts warns that the bend’s thick fibers are prone to cracking when bent, which is the same problem coming in from the other side. So the choice is not thin and weak against thick and strong. It comes down to which way you would rather lose, at that one spot on the case.

My opinion: that is the case for skiving a loop that wraps a flap pivot bar, or splitting a strap down, before forcing full-thickness leather around a tight radius. The cost is real. The CoOL figures say so, and so does the paring guide. A loop that cracks on day one costs more.

The vegetable tanning put that strength into the hide over weeks. Taking it back out should happen only where the case has no other way to bend.

Leather Skiving Knife Set, 2 Pieces: A two-piece metal skiving knife set for thinning leather edges. See it on Amazon (affiliate link).

As an Amazon Associate I earn from qualifying purchases. A commission may be earned if you buy through this link, at no extra cost to you.

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