CAD for laser-cut leather patterns
Stitch Hero brings five centuries of saddle-stitch tradition to the laser bed — a desktop CAD app whose stitch holes match your pricking iron tooth for tooth, and line up hole for hole across every piece you cut.
v0.2 · free while in development · macOS universal · Windows 10+ · MIT
Chord-true gaps that match a physical iron — on straights, around curves, through corners.
Duplicated, mirrored and seam-shared pieces punch identically. Every time, by construction.
Clean closed polylines for LightBurn or Illustrator — or print at true scale, tape and cut.
The idea
The saddle stitch has never been improved on. Two needles, one thread, every stitch locked on its own — a seam no machine can make. And the tool that spaces it hasn't changed either: a pricking iron's teeth are rigid steel, a fixed distance apart, and every leatherworker's rhythm is built around that pitch.
The drudgery deserves no nostalgia: wing dividers, tick marks, recounting holes around a corner and hoping two panels agree. A laser cuts and punches a whole pattern in seconds — if the file is right.
Stitch Hero exists to make the file right.
Problem 01 — corners
A traditional CAD tool marches holes a fixed distance along the contour (arc length). Around a rounded piece the corners land wherever they fall and the loop closes on a leftover gap. Stitch Hero auto-fits instead — it nudges the pitch a few percent per span so every corner is symmetric about its apex (a hole on it, or an even pair straddling it) and the whole loop closes evenly. No counting, no fudging.
Marched at a fixed 3.85 mm along the contour. Steady on the straights, but the corners land inconsistently and — the perimeter not dividing evenly — the loop closes on a crammed 1.5 mm gap where the stitching meets itself.
Auto-fit nudges the pitch a few percent per span (3.79 mm average here) so every corner sits symmetric about its apex and the loop closes even — all the way around. Computed, not counted.
The same auto-fit in the app — a strap end whose holes stay symmetric about the apex all the way around a full 180° cap, chord-spaced to the iron. No lone hole drifting off a bend, no crammed closure.
Problem 02 — registration
A front and its lining must share identical hole positions or nothing lines up at the bench. Stitch Hero guarantees it three ways —
Same outline + same settings = byte-identical hole layouts. Duplicate a panel and the holes already match — no re-punching, no drift.
Flip a piece to laser it from the back and every hole stays registered — slanted slits mirror too, so they line up when the piece is turned over.
Different outlines meeting on one edge — gusset against panel? Draw one stitch line and every piece against it gets exactly the same holes.
Make back piece (Ctrl+M) mirrors a panel and regenerates its stitching so the two register hole-for-hole — laser one from the front and one from the back and they still line up. Same outline, same settings, byte-identical holes.
"The romance is in the stitching — not in marking out four hundred holes with a wing divider and a prayer."
The drawing bench
Not a plugin, not a spreadsheet of coordinates — a proper millimeter-true drafting tool that happens to know what a pricking iron is.
Rectangles, circles by 2 or 3 points, polygons, 3-point arcs and a vector pen with bezier handles. Arcs stay arcs — node-edit everything.
Click the part of an outline you don't want; it's cut back to the nearest intersections. Arcs survive, closed shapes open, open paths split.
Endpoints, midpoints, centers, quadrants, intersections, stitch holes — with Illustrator-style alignment guides and construction lines.
Millimetre-true canvas, type-in sizes, a live measure tool, and dimension annotations that track the shapes they're pinned to.
Color-coded Cut / Score / Engrave / Stitch layers map straight onto laser operations. Hide Cut to inspect just the stitching.
Per-shape irons from 2.0–5.0 mm or SPI, in four punch shapes — round, oblique, French, diamond — rendered and exported with the true tooth.
SVG and DXF as clean closed polylines LightBurn understands, JSON projects, and 1:1 tiled PDF for tape-and-cut.
Bring existing SVG or DXF drawings in as editable shapes — or drop a photo behind the canvas, calibrate it to real millimeters, and trace over it.
Boolean union, difference and intersect punch windows and card slots straight out of a panel — and offset an outline for a true seam allowance.
Shape-aware nesting packs your pieces onto a sheet to save leather, and kerf compensation grows each cut by half the beam so parts come out drawn-size.
Leather area and waste, saddle-stitch thread length, and a full cost breakdown when you feed it your prices.
The workflow
Sketch your pieces in millimeters — snap, trim, radius the corners, type exact sizes.
Pick your iron. Chord-true holes flow around the outline — symmetric, fitted, registered.
Export layered SVG or DXF straight into LightBurn — cut, score, engrave and punch in one job.
Two needles, one thread. The holes line up — because they were never allowed not to.
Ready-to-run builds for both platforms — no setup, no dependencies. Open the app, draw a card holder, and burn it tonight.