A leather panel on a workbench with one rounded corner, surrounded by a corner punch, round knife, ruler and washer.
| |

Rounding Corners Cleanly

ByPeter Joeseph 'Briefcase Maker' Kalafatis

A square corner snags a sleeve, catches a door frame and frays first. A round one has to be cut right.

Rounding a leather corner looks like the easiest cut on the piece and is the one people look at first. The eye goes to the corner of a case before the stitching, before the hardware, because that’s where the outline turns, and a flat spot or a little hook in the curve shows from across a room. My page on The Maker says hand stitching lets me get shapes and corners a machine can’t, but the stitching only follows the cut. If the curve is wrong, the stitches trace the mistake. So this is a buyer’s guide to the tools that make that curve, what each does well and where each lets you down.

Video: How to Use the Corner Round Leather Punch, from The Leather Guy on YouTube.

Corner punches

One strike, one radius, the same corner every time.

Hands holding a corner punch upright on bridle leather over a poly board, about to strike with a rawhide mallet.

A corner punch is a curved blade on a handle that you stand on the corner and hit. It’s the fastest clean corner there is, and the reason people buy one is repeatability. Four corners on a card holder come out the same because the steel decides the curve, not your wrist.

Tandy Leather sells the Craftool Japanese round corner punch in three sizes, with radii of 1.0, 1.5 and 2.0 centimeters, listed at $44.99 to $49.99 when I checked. The page says to strike it with a non-metallic mallet and adds, “For best results and extended tool life, use over a Poly Cutting Board.” Sailrite’s 1-inch radius corner punch is listed at $49.30, and its page tells you to “pair this punch with a leather maul and cutting board.” At the top end, Leatherbox carries a Kevin Lee set of seven round corner punches in carbon steel, from 10 to 40 millimeter radius, at €164.95, though the page showed it as unavailable.

Follow the mallet advice. My opinion: a steel hammer has no business on the top of a punch, and Tandy’s note about tool life tells you what a hard surface under the blade does to the edge. The poly board gives the steel something to cut into.

Here is the gap. None of those three pages says how thick a leather the punch will take. That matters on heavy bridle. A punch that falls through a thin wallet card in one blow may need several on a thick panel, and every extra blow is a chance for the tool to shift. My opinion: hold the punch dead upright, keep it pressed down between blows, and if it moves, stop and look before you hit again.

The other limit is the radius itself. A punch gives you exactly one curve. Briefcase panels often want a bigger, looser corner than any small punch makes, which is where the knife comes back in.

Strap end punches

Built for straps. Both corners in a single blow.

A strap end punch rounds the whole end of a strap, both corners and the line between them, at once. It’s a different tool from a corner punch, sized by strap width instead of radius. Weaver Leather Supply’s round strap end punch comes in widths from 1/2 inch to 1-1/2 inches, made from hand-forged carbon steel with a polished barrel, listed at $40.50 when I checked.

For a belt, a leash or a closure strap this is the tool. The end comes out centered on the strap, which is the hard part to do by eye, because a strap end that’s off center by a hair looks crooked on every buckle it goes through.

Buy it to match the strap width you actually cut. A punch that’s a size too wide leaves a shoulder on each side, and one too narrow nibbles the edges. Neither can be fixed without cutting the strap shorter and trying again.

A strap end punch won’t help with a panel corner. It only knows straps. If you make cases and nothing with a buckle tongue, skip it.

A knife, a washer and a French curve

Cheapest tools in the shop, and the hardest to use well.

Macro of a burnished rounded corner on bridle leather with stitching holes following the curve.

Before anybody sold corner punches, people traced something round and cut. That still works, and on big corners it is often the only thing that does. In a 2010 leatherworker.net thread on making perfectly round corners, one member traced steel fender washers with a craft blade and touched up the edge with sandpaper. Another, Kevin, rocked a round knife around the line “like you’re just taking off a little chip at a time,” moving the leather as he went. He said cutting a curve in one long pass stretches the leather, and taking it in chips doesn’t.

For briefcase-size corners, a 2007 thread on rounding corners on a briefcase had makers drawing the curve freehand and then matching it with a drafting tool. One of them, Art, explained why: “The French Curve allows you to vary the radius of the curve.” A corner that isn’t a perfect quarter circle often looks better on a big panel, softer at one end, tighter at the other. Another member in that thread traced a washer onto stiff illustration board to make a template he could reuse.

There is a third road between the punch and the knife. In a 2017 thread on getting nice round corners, Dwight described grinding a sharp bevel on the end of a piece of steel conduit, cutting it to a half or a quarter circle, and striking it like a punch after dampening the leather. With the leather damp, he said, “they go through like hot butter.” Another member punched a round hole in each corner and joined the holes with straight cuts.

The knife is the cheapest tool here and the one that asks the most of you. Keep it sharp enough to shave. Hold the blade upright so the edge stays square to the face, and cut the curve in short strokes, turning the leather toward the blade rather than dragging the blade around the leather. A dull knife on a curve doesn’t cut. It pushes and then it jumps.

Finishing the corner after the cut

The cut sets the curve. Sanding, beveling and the stitch line decide whether anyone notices it.

No cut comes off perfect. A light pass with sandpaper wrapped on a flat stick, or an edge rasp, takes out the flat spots and the little steps where one stroke met the next. Sand along the curve, never across it, and check it by running a fingertip around the edge with your eyes shut. The finger finds a flat spot that the eye forgives.

Then bevel and burnish it the same way as the straight edges, which I covered in beveling and creasing a leather strap and in hand burnishing edges on vegetable-tanned leather. I burnish by hand because that’s the tradition, and the corner is where hand burnishing earns its time. A beveler wants to skip off a tight curve, so take it slower there and roll your wrist with the turn.

The stitch line is the last test. Weaver’s page on choosing a stitching chisel says a single-prong chisel is “Used for corners and tight curves,” while a two-prong helps on gentler ones. In a 2020 thread on diamond chisels on round corners, one maker started at the center of the bottom edge and worked out to each side, so both runs met the top evenly. Another said that on a curve you should only press one prong lightly into the last hole to mark the next spot, because seating it hard stretches that hole and twists the angle.

That matches how I work. Around a curve I punch one step at a time, never a full chisel at a run, and on thick leather every hole gets punched and lined up before a needle goes near it. Thick work won’t stitch any other way. A corner punched in a hurry gives you holes that fan out like a bad haircut, and the thread shows it on both sides.

Which one to buy

Buy for what you make most. Then learn the knife anyway.

A finished bridle leather document case with four matching rounded corners and hand stitching following each curve.

Small goods, wallets and card holders: a corner punch in one or two radii. It’s quick and it repeats, and the poly board and soft mallet come with it whether the box says so or not. Straps and belts: a strap end punch in the widths you cut. Big panels: no punch on the market will make that corner for you, and a washer, a French curve and a knife will. If money is short, start with the knife and a washer, because every other method here still needs a sharp blade at some point.

Now the part that cuts against everything above. I just spent a whole guide selling templates and punches, and I don’t use templates. I work my briefcases out with a ruler and my eye, the way a sculptor works, and when I have used templates at all it was for bags made for me in a factory run, not the ones I build by hand. Each corner on a case gets drawn and cut on the bench. That isn’t a boast. It’s slower, and there’s nothing to copy from one corner to the next.

So, in my view, the punch is the better buy for most people, and I’m the wrong man to ask if you want proof of it. The tool that never moves will give you four matching corners on the first day. The eye takes years, and a ruler, and a lot of offcuts, and it still has days when it lies to you.

If you are cutting a briefcase out of a bridle leather bend, cut the panel square first. Round it last, when every other line is already true.

SELMAIDY 5 Pcs Arc-Shaped Leather Punch Set: A five-piece arc-shaped punch set for rounding corners. See it on Amazon (affiliate link).

OWDEN 9 Pieces Leather Hollow Punch Set: A nine-piece hollow punch set for round holes. See it on Amazon (affiliate link).

WUTA Leather Carving Hammer: A poly-head maul for leatherwork. See it on Amazon (affiliate link).

Leather Round Knife with Wooden Handle: A round knife with a wooden handle for cutting leather. See it on Amazon (affiliate link).

Farberware 12 x 18 Inch Reversible Plastic Cutting Board: A reversible plastic cutting board, 12 by 18 inches, usable as a cheap cutting surface under a knife. 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.

Sources

You Might Also Like

Similar Posts

Leave a Reply