Diamond stitching chisel and French-style pricking iron side by side on a workbench with bridle leather.
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Diamond Chisels and French Chisels

ByPeter Joeseph 'Briefcase Maker' Kalafatis

Two tools that make the same holes on paper, and two different seams on the leather.

Diamond chisels and French chisels both punch a row of slanted holes for a saddle stitch, and the argument over which one to buy goes on forever on the forums because both camps are partly right. The diamond chisel is a set of long, angled prongs with a diamond cross-section that you drive straight through the work. The French-style iron, which plenty of sellers still call a pricking iron, has thinner, flatter teeth and leaves a slit that lays the thread down at a cleaner angle. Same job. Different ends. The way to see the difference is to follow the work from the first line on the leather to the last stitch pulled tight, and see where each tool earns its place.

Video: Punching Stitching Holes on Vegetable Tanned Natural Leather, from Marcellino NY Briefcase Maker on YouTube.

Names first, because the catalogs mix them up

Pricking iron, stitching chisel, French iron: three names, at least two tools.

Hand holding a diamond stitching chisel upright on thick bridle leather before a mallet strike.

Before you buy anything, sort out the words. Sellers use them loosely and you will pay for it.

On Leatherworker.net, a member called Markwell laid out the split in a thread on pricking irons, stitching chisels and lacing chisels. A pricking iron, in the old sense, only marks where the holes go, and you finish each one with an awl. A stitching chisel marks and pierces in one blow. In another thread on irons, chisels and holes, a member called zuludog adds the shapes: the pricking iron has short prongs that leave shallow marks, while the stitching chisel has long, narrow prongs with a diamond cross-section, set at an angle to the body.

Then the French-style iron muddies it. Maze Leather’s guide to leather stitching tools treats the pricking iron and the French-style chisel as one tool with a distinctive slanted tooth, and says it only goes about halfway through the leather, so an awl finishes the hole. Rocky Mountain Leather Supply sells its French-style premium pricking irons as tools whose thin teeth pierce the leather easily. One name, two behaviors. Whether a given French iron marks or punches depends on how long its teeth are and how thick your leather is.

So read the tooth length, not the name. The rest of this walkthrough treats a diamond chisel as the long-pronged punch-through tool and a French iron as the thin-toothed, slanted tool that may or may not go all the way.

Mark the line and choose the spacing

The tool you pick sets how many stitches land in every inch.

The first thing on the leather is a line, not a hole. Weaver’s hand-sewing instructions set a groove 1/8 inch from the edge before any chisel comes out. Every hole follows that groove, so if the groove wanders, the seam wanders with it.

Then spacing. This is where the catalogs actually help. Weaver’s diamond stitching chisel set comes in 3, 4, 5 and 6 mm, which it gives as 9, 7, 6 and 5 stitches per inch. Rocky Mountain’s French-style irons run from a #7 at 3.85 mm (6.6 stitches per inch) to a #10 at 2.7 mm (9.4). The Vergez Blanchard irons sold by the same shop go from a #5 at 5.4 mm, about 4.7 to the inch, down to a #14 at 1.9 mm, about 13.4.

Read those side by side and the pattern is plain. The French tradition goes much finer at the small end. The diamond sets cluster in the middle, around the spacings people use for bags, belts and straps.

The post on reading a maker’s stitch count explains what a buyer sees in that number. From the bench side, my opinion is short. Buy one spacing and learn it before you buy three. A seam is a row of small decisions, and you want the tool to be the one thing in it that does not change.

Punching through thick bridle

Square to the bench, one blow at a time, and wax on the teeth.

Macro view of diamond chisel holes beside thin slanted French iron slits in vegetable-tanned leather.

Now the holes. On thin leather the two tools behave close to the same. On thick bridle they split apart.

A diamond chisel is built to go through, and the Maze guide credits it with getting through a thick layer of leather. Weaver’s sewing page gives the rules: keep each chisel straight up and down, strike with a rawhide mallet, work on a poly board so the teeth do not ding, set the first tooth in the last hole you made to keep the spacing even, and rub beeswax on the chisel so it comes back out without lifting the leather.

A French iron with short teeth often will not go through heavy stock at all. In a Leatherworker.net thread asking whether a pricking iron can stand in for a stitching chisel, one member, chrisash, notes that pricking irons have very short blades, about 5 mm at most, and treats them as markers that set the spacing for an awl. Another, Tugadude, says they pierce thin leather well and that an awl is the easier road on very thick work.

On thick work, I pre-punch and line up every hole before a needle comes near it, because heavy bridle will not stitch any other way. My hand-stitching page admits what that costs. Hand stitching “tends to have slightly bigger holes because they are punched by hand.” The same page says the hand is limited to how small it can go, especially with thick bridle saddlery leather. That sentence matters more than any tooth profile. On a briefcase gusset, the leather sets the floor on hole size, whatever the tool in your fist.

The post on punching stitch holes in thick bridle leather goes further into that part.

Corners and curves

The short iron does the hard part of every seam.

A straight run is easy with either tool. Line up, strike, step, strike. Curves are where seams go wrong.

Both traditions solve it the same way: a short tool. Rocky Mountain sells its French-style irons as single teeth, 20-tooth bars, or sets of 2, 5 and 9 teeth. The Vergez Blanchard sets come as a 2-tooth iron for curves and a wider iron, roughly an inch, for faster work on the straights. Weaver’s diamond sets carry 1, 2, 4 and 6 prong tools in most sizes. The long tool covers ground. The two-prong walks you around the corner.

I punch around a curve one step at a time, a hole or two per strike, letting the line turn under the tool rather than forcing the tool to turn on the line. Go too fast with a long bar on a curve and the outer teeth land off the groove, like a nail gun with the safety off. Then you have holes you cannot take back.

Keep the tool square to the bench and the line will forgive a lot. Tip it, even a little, and the holes on the back come out somewhere other than where you aimed. On a thin wallet nobody sees that. On a three-layer seam through heavy bridle, the back is half the job.

What the seam looks like after

The French slit lays the thread down. The diamond hole lets it sit up.

Finished saddle-stitched seam on a bridle leather briefcase gusset with harness needles and pliers.

Pull the thread through and the two tools start to tell on themselves.

The Maze guide says the diamond chisel’s holes can leave the back of the work frayed, which it calls a “not so perfectly flush stitch.” It credits the French-style iron with a high-end look, with very little thread showing. That matches the reason people buy French irons: thinner teeth, a narrower slit, and thread that sits down in the leather at a steady slant instead of standing proud of it.

The other half of the job is the needle. Weaver uses two harness needles on one thread, cut about four times the seam length. On very thick leather I wax the needles and pull them through with pliers, because fingers alone will not do it all day. Three layers of the heaviest bridle, gusset and panel and pocket, is hard on the hands whatever made the holes. The Maze guide says French irons limit you to thread up to around 0.6 mm. A briefcase seam often wants more thread than that.

Then check both faces. My Maker page puts the standard in one line: “The side nobody sees is where a weak stitch gets found out.” A pretty face and a chewed back is a seam that lied to you.

Where the pretty tool loses

On thin goods the French iron wins. On a briefcase, it gets close to even.

Here is the argument for the French iron, and I mean it. It makes the finer seam. The thread lies flatter, the slant is cleaner, and at the small spacings it does things a diamond chisel cannot. If I were making a card wallet out of thin calf, I would reach for one.

Now the reversal. Almost none of that survives thick bridle.

The teeth that make the French slit so fine are the same teeth that stop short in heavy leather, which puts an awl back in your hand for every hole. The thread limit on the Maze page rules out the heavier thread a bag seam wants. And the finest spacing in the Vergez Blanchard range is wasted on leather that, by my own page’s account, sets a floor on how small a hand-punched hole can get. Even the prestige name is no guarantee. In the thread on using a pricking iron as a chisel, a member called TomE reports a Vergez Blanchard iron with “Stubby teeth with rough unfinished edges” that took hours of work, and says he is happier with Rocky Mountain’s. That is one man’s iron and not a verdict on the firm, which Dictum lists as making tools in France since 1823. The bench does not care what the catalog says.

My opinion: the pretty tool loses on thick stock, and the diamond chisel, with its crude back, comes closer to even there than its reputation says. On heavy bridle the angle you hold matters more than the tooth profile, and a consistent hole beats an elegant one. If you mostly stitch thin goods, buy French. If you stitch belts, straps and bags, start with a diamond set and a good awl, and keep the French iron for the day you make something small. The post on whether a complete tool kit saves money weighs the buying side.

Japanese diamond-style irons, like the Kevin Lee set at Leatherbox in 3, 4 and 5 mm, which the seller says punch thicker leather smoothly, sit somewhere between the two. I would want to see one go through a gusset before I said where.

Weaver Leather Supply Diamond Leather Stitching Chisel Set: A set of 4 mm diamond stitching chisels for punching saddle-stitch holes. See it on Amazon (affiliate link).

General Tools Scratch Awl with Hardwood Handle: A scratch awl with a hardwood handle. See it on Amazon (affiliate link).

WUTA Wing Divider: An adjustable stainless steel wing divider for marking a stitch line. See it on Amazon (affiliate link).

Leather Carving Hammer Mallet: A nylon-headed mallet with a wooden handle for striking chisels. See it on Amazon (affiliate link).

Beesworks Yellow Beeswax Bars, 6 oz: Yellow beeswax bars, 6 oz, for waxing thread. See it on Amazon (affiliate link).

Aiskaer Leather Stitching Punch Set: A diamond-tooth stitching punch set. 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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