Got bits of high-carbon steel too small for a full knife? Perfect. A kiridashi—the traditional Japanese marking/utility knife—is a brilliant way to turn scrap into something sharp, useful, and gift-worthy. You’ll practise profiling, heat-treating, and chisel-grind sharpening on a project you can finish quickly and use every day in the workshop.
What is a Kiridashi?
A kiridashi is a compact, single-bevel knife used by Japanese carpenters and makers for marking lines, scoring, carving, opening boxes, trimming leather, and general workshop chores. Traditionally laminated, but a simple monosteel version from offcuts works beautifully. Because it’s chisel-ground (bevel on one side, flat on the other), it teaches excellent control and sharpening fundamentals.
Why it’s a great scrap-steel project
- Uses small pieces: 3–6 mm thick, 20–25 mm wide, 80–120 mm long.
- Skill builder: layout, bevel control, heat-treat, and scary-sharp finishing.
- Actually useful: lives on your bench; also makes a tidy gift with a quick sheath.
Materials & Tools
- Offcut of high-carbon steel (1084/1095/80CrV2/5160, old file or leaf spring)
- Angle grinder or hacksaw; files; belt grinder (optional)
- Drill + 4–6 mm bit (lanyard hole, optional)
- Forge or torch for heat-treat; canola oil for quench
- Sandpaper (120 → 400/800+), stones or diamond plates, strop
- Oven for tempering, magnet, PPE
- Paracord or leather strap for a simple wrap; scrap leather for a sleeve
Tip: If you’re using hardened scrap (old file), anneal first: heat to dull red and let it cool slowly in vermiculite/ash or in the turned-off forge.
Typical Dimensions & Geometry
- Overall length: 90–120 mm
- Thickness: 3–5 mm (stout and comfortable)
- Tip angle: 30–45° from the spine
- Bevel angle: ~20–25° on the bevelled side
- Micro-bevel (optional): +1–2° for durability
Handedness: For clean layout cuts, you usually want the flat face against your straightedge/workpiece. Choose the bevel on the opposite side to match how you naturally hold and mark (right- or left-handed).
Step-by-Step: Making a Kiridashi from Offcuts
- Choose & Prep the Steel
Spark-test if you’re unsure it’s high-carbon. Degrease, remove heavy scale, and square the blank. If starting from a file, grind off the teeth. - Lay Out the Shape
Scribe a straight spine and a 30–45° nose. Add a subtle belly on the edge if you like. Mark a lanyard hole at the tail (optional). - Profile the Blank
Cut/grind to your lines. Break all sharp corners on the spine and handle for comfort. You can hammer dimples in the handle for a textured grip. Drill the lanyard hole now. - Establish the Chisel Bevel
Pick your handedness. File or grind a single bevel to ~20–25°, leaving ~0.3 mm of edge (don’t go to zero before heat-treat). Keep the flat side truly flat—that’s key to clean marking. - Normalise (especially for forged or mystery steel)
Heat to just above critical (non-magnetic), air cool to black—3 cycles, reducing heat each time. This refines grain and reduces warps. - Harden
Heat evenly to critical; quench tip-first into warm canola oil. Test with a file— it should skate on the edge. (If it doesn’t harden, your steel may be low-carbon.) - Temper
Clean the blade; temper in an oven 200–220 °C for 2 × 1 hr, cooling to room temp between cycles. Aim for a tough, working edge. - Finish Grind & Sharpen
- Thin the bevel to the edge and true the flat face.
- Progress through stones (e.g., 400 → 1000 → 3000+).
- Add a tiny micro-bevel for durability.
- Strop on leather with compound until it bites fingernail easily.
- Handle Comfort & Wrap (Optional)
Chamfer the spine/choil. Wrap the handle with paracord or a leather strip; seal with thin CA or wax. If you take out the core of the paracod you will have a flatter cord for the wrap. Punch out a quick leather sleeve from offcuts for a safe pocket carry. - Etch & Oil
Add your maker’s mark, wipe with camellia/mineral oil, and call it done.
Using Your Kiridashi
- Accurate layout lines in timber (flat face to rule)
- Scoring veneer, leather, and fibrous packing
- Trimming shims, paring end grain, opening boxes
- A tidy gift for a mate—include a note about handedness!
Troubleshooting
- Warp after quench? Temper once, then gently clamp between flat plates while warm; re-temper.
- Edge micro-chips? Increase the micro-bevel a touch or temper 10–15 °C hotter.
- Doesn’t harden? You may have mild steel—save it for a tool and try a known high-carbon offcut.