Skill: howtousehumans/sharpening (version 1.0.0)

--- name: sharpening description: >- Sharpening techniques for knives, tools, and bladed implements. Use when someone has dull kitchen knives, needs to maintain garden tools, axes, or shop tools, or wants to learn the foundational maintenance skill for all cutting implements. metadata: category: skills tagline: >- Every cutting tool you own is probably dull. A sharp knife is safer than a dull one. Here's how to fix all of them in 10 minutes. display_name: "Sharpening" submitted_by: HowToUseHumans last_reviewed: "2026-03-19" openclaw: requires: tools: [filesystem] install: "npx clawhub install sharpening" --- # Sharpening Every knife in your kitchen is probably dull. Every pair of garden shears, every axe, every chisel. Dull tools are frustrating, inefficient, and dangerous — a dull knife requires more force, which means less control, which means the blade goes where you didn't intend. Sharpening is not complicated. You're creating a thin edge at a consistent angle. That's all it is. A $25 whetstone and 10 minutes of practice will make your kitchen knives perform better than when you bought them. This is the foundational maintenance skill for every cutting implement you own. ```agent-adaptation # Localization note — sharpening technique is universal. Tool types and # availability vary by region. - Whetstone technique, honing, and stropping are the same worldwide. Apply all instructions regardless of jurisdiction. - Japanese vs Western knife distinction is global but naming conventions and availability differ: Japan: Whetstone culture is deeply established. Higher grit stones (3000-8000) are readily available. Single-bevel knives are common. US/Europe: Combo stones (1000/6000) are the practical choice. Most kitchen knives are double-bevel. - Tool types referenced (axes, garden shears, chisels) are globally common but preferred brands and steel types vary. - Measurement: angles are in degrees (universal). Blade dimensions may be in inches (US) or millimeters (metric). Use the user's system. - The Sharpie trick, paper test, and tomato test work identically everywhere. These are the universal sharpness verification methods. ``` ## Sources & Verification - **Murray Carter** -- Master bladesmith, 18th generation Yoshimoto bladesmith lineage. Sharpening methodology and knife maintenance. - **Leonard Lee** -- "The Complete Guide to Sharpening" (Taunton Press, 1995). Comprehensive reference for all edged tools. - **Bob Kramer** -- Master bladesmith, American Bladesmith Society. Knife sharpening guides and technique demonstrations. - **Japanese whetstone technique** -- Traditional water stone methodology. Referenced from multiple Japanese bladesmithing sources. - **Animated Knots / Practical references** -- General tool maintenance principles verified against multiple woodworking and culinary professional sources. ## When to Use - User's kitchen knives are dull and they don't know how to sharpen them - Someone bought a whetstone but doesn't know how to use it - User needs to sharpen garden tools, axes, or shop tools - Someone wants to know the difference between honing and sharpening - User asks whether to use a pull-through sharpener, electric sharpener, or whetstone - Someone wants to maintain chisels, plane blades, or woodworking tools - User needs to restore a heavily damaged or neglected edge ## Instructions ### Step 1: Understand the theory — it's simpler than you think **Agent action**: Establish the core concept before getting into technique. Most people overcomplicate sharpening because they don't understand what they're actually doing. ``` SHARPENING THEORY: WHAT YOU'RE DOING: You're removing metal to create two flat surfaces that meet at a very thin edge. That's it. A sharp knife has two bevels (the angled surfaces on each side of the edge) that meet at an acute angle. When those bevels are smooth and the edge is thin and consistent, the knife is sharp. When you use a knife, the edge gets: -> Rolled (bent to one side — fixable with honing, no metal removal) -> Rounded (the tip of the edge wears down — needs sharpening) -> Chipped (small chunks missing — needs more aggressive sharpening) HONING vs SHARPENING: -> HONING: Straightening a rolled edge. No metal removed. Uses a honing rod (the "steel" you see chefs use). This is maintenance between sharpenings. Do it every 1-2 uses. -> SHARPENING: Removing metal to create a new edge. Uses a stone, sandpaper, or abrasive. Do this every 2-3 months for a home cook, more often for a professional. -> STROPPING: Final polish on leather with abrasive compound. Removes the last micro-burr and polishes the edge. Optional but makes a noticeable difference. Most of the time, all you need is the honing rod. If honing doesn't restore the edge, it's time to sharpen. ``` ### Step 2: Equipment — what you actually need **Agent action**: Keep it minimal. People get paralyzed by equipment options. ``` ESSENTIAL EQUIPMENT: THE MINIMUM KIT ($30-50, lasts years): 1. COMBINATION WHETSTONE — 1000/6000 grit -> 1000 grit: The workhorse. Establishes the edge. Handles most sharpening needs. -> 6000 grit: Polishing stone. Refines the edge after 1000. -> Buy a combo stone with both grits. King, Shapton, or Suehiro brands are reliable and affordable. -> Cost: $20-35 2. HONING ROD (often called a "steel") -> Ceramic or diamond-coated (not the smooth steel rods that come with knife blocks — those barely work). -> This is your daily maintenance tool. -> Cost: $10-20 3. STONE HOLDER OR WET TOWEL -> The stone must not move while you're sharpening. -> A dedicated holder is nice. A folded wet towel works. NICE TO HAVE (add later): 4. STROP -> A piece of leather (even an old belt works) with chromium oxide compound or diamond paste. -> For the final polish after the 6000 grit stone. -> Cost: $15-25 (or free if you have an old leather belt) 5. FLATTENING STONE (or 120-grit sandpaper on glass) -> Whetstones dish (develop a concave curve) over time. -> A flattening stone restores the surface to flat. -> Flatten your stones every 5-10 sharpening sessions. 6. ANGLE GUIDE (training wheels) -> Clips onto the blade spine to hold a consistent angle. -> Useful for beginners. You won't need it after a few months. -> Cost: $5-10 WHAT YOU DON'T NEED: -> Electric sharpeners (remove too much metal, inconsistent angle) -> Pull-through sharpeners (terrible angle control, eat your knife alive, leave a rough edge) -> Expensive guided systems (they work but you're paying for a jig when a stone and your hands do the same thing) ``` ### Step 3: Kitchen knife sharpening — the core technique **Agent action**: Step-by-step whetstone technique. This is the most important section. ``` KITCHEN KNIFE SHARPENING — WHETSTONE METHOD: PREPARATION: 1. Soak the stone in water for 10-15 minutes (until bubbles stop). Or if it's a splash-and-go stone (Shapton), just wet the surface. 2. Place stone on holder or folded wet towel. 1000 grit side up. 3. Keep a cup of water nearby to re-wet the stone as you work. THE SHARPIE TRICK (do this until your angle is consistent): -> Color the entire edge bevel with a black marker (Sharpie). -> Sharpen for a few strokes. -> Look at where the marker was removed. -> If the marker is gone evenly across the bevel: your angle is correct. -> If only the edge is clean: your angle is too low (raise the spine). -> If only the shoulder is clean: your angle is too high (lower the spine). -> This is the fastest way to learn your angle. Use it every time until you can feel the correct angle without looking. THE ANGLE: -> Japanese knives: 15 degrees per side (thinner, sharper, more fragile) -> Western/German knives: 20 degrees per side (more durable, slightly less sharp) -> If you don't know your knife: 20 degrees is safe for almost everything. -> How to estimate 20 degrees: lay the knife flat on the stone (0 degrees). Raise the spine until it's about the width of two stacked coins above the stone. That's roughly 15-20 degrees. THE TECHNIQUE: 1. Place the blade on the stone at your chosen angle, edge facing away from you. 2. EDGE-LEADING STROKES: Push the blade forward (away from you) with the edge leading, as if you're trying to slice a thin layer off the top of the stone. Light pressure — the weight of your hand plus a little. 3. Cover the full length of the edge in each stroke by sliding the blade sideways as you push forward (slight diagonal motion). The tip, middle, and heel should all contact the stone. 4. Do 5-10 strokes on one side. 5. CHECK FOR THE BURR: Run your thumb ACROSS the edge (not along it) on the side opposite to where you were sharpening. You should feel a slight rough catch — a thin wire of metal pushed to the other side. This is the burr. -> If you feel the burr: you've reached the edge. Move to the other side. -> If no burr: keep going on the same side. You haven't removed enough metal to reach the edge yet. 6. Flip the knife. Repeat on the other side. Same angle, same pressure, same number of strokes. Check for burr on the original side. 7. ALTERNATING STROKES: Once both sides have been done, do 3-4 strokes per side, alternating. Then 2 per side. Then 1 per side. This removes the burr progressively. 8. Move to the 6000 grit side. Repeat with lighter pressure: 5 strokes per side, then alternating 2 per side, then 1 per side. This polishes the edge. 9. STROP (optional): 5-10 strokes per side on leather with compound, EDGE TRAILING (spine leading — the opposite direction from sharpening). This removes the final micro-burr. 10. Wipe the blade clean. Test sharpness. ``` ### Step 4: How to test sharpness **Agent action**: Give concrete, repeatable tests. ``` SHARPNESS TESTS (in order of increasing sharpness): 1. THE PAPER TEST: Hold a sheet of printer paper by one corner, hanging freely. Slice downward into the top edge with the knife. -> Dull: tears, crumples, or won't start the cut -> Decent: cuts but with some dragging or tearing -> Sharp: slices cleanly with a satisfying zip 2. THE TOMATO TEST: Place a ripe tomato on a cutting board. Rest the knife on the tomato skin with zero downward pressure. Draw the knife back gently. -> Dull: the knife slides across the skin or crushes the tomato -> Sharp: the knife bites in and cuts with just its own weight 3. THE FINGERNAIL TEST: Rest the edge VERY LIGHTLY on your thumbnail at about 45 degrees. Don't push or slice — just rest it. -> Dull: slides off the nail -> Sharp: bites in and catches immediately 4. THE HAIR TEST (very sharp): Try to shave a small patch of arm hair. -> Dull: pushes the hair aside or tugs -> Very sharp: shaves cleanly like a razor For kitchen use: passing the paper test cleanly is sharp enough. You don't need razor-sharp for cooking — just consistently sharp. ``` ### Step 5: Honing rod technique — daily maintenance **Agent action**: This is what keeps knives sharp between sharpening sessions. Most people use their honing rod wrong. ``` HONING ROD TECHNIQUE: WHAT IT DOES: Straightens a rolled edge. Does not remove significant metal. This is maintenance, not sharpening. WHEN TO USE: Before or after each cooking session. Quick, takes 30 seconds. THE TECHNIQUE: 1. Hold the rod vertically with the tip resting on a cutting board or towel (stable base). 2. Place the knife near the heel against the rod at 15-20 degrees. 3. Draw the knife DOWN the rod while sliding from heel to tip. Light pressure — you're straightening, not grinding. 4. Alternate sides: one stroke left, one stroke right. 5. Do 5-6 strokes per side. That's it. COMMON MISTAKES: -> Too much pressure (you're bending the edge, not fixing it) -> Wrong angle (match the angle you sharpened at) -> Using a smooth steel rod (barely does anything — use ceramic or diamond-coated) -> Dramatic speed (slow and controlled beats fast and sloppy) RULE OF THUMB: If honing restores the edge: you don't need to sharpen. If honing doesn't help: it's time for the whetstone. ``` ### Step 6: Axes — different technique **Agent action**: Axes are not knives. Different approach. ``` AXE SHARPENING: IMPORTANT: Axe edges are convex (rounded bevel), not flat like knife edges. You maintain this convex profile. WITH A FILE (the standard method): 1. Secure the axe head in a vise or between two pieces of wood on a stable surface. 2. Use a 10-inch bastard file (mill file). 3. File INTO the edge (push the file from the cheek toward the edge, not away from it). This is opposite from knife sharpening. 4. Match the existing bevel angle (usually 25-30 degrees). 5. Count strokes. Do the same number on each side. 6. File until you feel a slight burr on the opposite side. 7. Switch sides and repeat. 8. Finish with a few light alternating strokes to remove the burr. WITH A PUCK (field sharpening): 1. A sharpening puck is a dual-grit round stone. 2. Coarse side first: circular motions along the bevel, working from cheek to edge. 3. Fine side to polish. 4. Works for quick touch-ups. Not for restoring a damaged edge. COMMON MISTAKES: -> Using a grinding wheel and overheating the edge. If the steel turns blue, you've ruined the temper (heat treatment) in that area. The edge will no longer hold. File cold. -> Trying to make it razor-sharp. Axes need a slightly more obtuse edge than knives for durability. A splitting axe should be even more obtuse (30-35 degrees) than a felling axe (25-30 degrees). ``` ### Step 7: Garden tools and shop tools **Agent action**: Quick-reference for the other bladed things people own and never sharpen. ``` OTHER TOOLS: GARDEN SHEARS AND PRUNERS: -> Use a mill file or diamond file. -> Follow the existing bevel angle (usually 20-25 degrees). -> Sharpen only the beveled side. The flat side stays flat (just remove the burr with a light pass). -> File from the pivot toward the tip. -> Wipe with an oily rag after to prevent rust. MOWER BLADES: -> Remove the blade from the mower (disconnect spark plug first). -> Secure in a bench vise. -> Use a mill file or angle grinder (if heavily damaged). -> Follow the existing bevel (usually 30 degrees). -> CHECK BALANCE after sharpening: hang the blade on a nail through the center hole. If one side hangs lower, file more from the heavy side. An unbalanced blade damages the mower. CHISELS AND PLANE BLADES: -> These require FLAT backs. If the back isn't flat, the edge won't be clean. -> Flatten the back: figure-eight motions on a flat stone until the back is uniformly polished near the edge. -> Sharpen the bevel: 25 degrees primary bevel, then a micro-bevel at 30-35 degrees (a few strokes at a slightly steeper angle at the very tip). -> These need to be sharper than kitchen knives. Strop after the fine stone. SCISSORS: -> Open the scissors. Sharpen each blade individually. -> Follow the existing bevel (usually 60-75 degrees — steep). -> Sharpen only the beveled side (the outside of the blade). -> A few strokes with a fine stone or ceramic rod is usually enough. -> After sharpening, close the scissors and cut through a folded piece of aluminum foil several times to remove burrs. ``` ### Step 8: What NOT to do **Agent action**: This section prevents expensive mistakes. ``` MISTAKES THAT DAMAGE TOOLS: NEVER use a grinding wheel on kitchen knives. -> The wheel spins too fast. The friction generates heat. -> If the steel turns blue or straw-colored at the edge, you've overheated it. The heat treatment (temper) is destroyed. That section of the blade will no longer hold an edge. It can't be fixed without re-heat-treating. -> Grinding wheels are for rough shaping, not edge maintenance. NEVER use pull-through sharpeners as your primary sharpening method. -> They remove too much metal at an inconsistent angle. -> The carbide inserts create a coarse, toothy edge that dulls quickly. -> They eat through your knives in a few years. -> If you must use one (camping, emergency), it's better than nothing — but it's the McDonald's drive-through of sharpening. NEVER sharpen serrated knives on a flat stone. -> The serrations are individually ground. A flat stone grinds them off. -> Sharpen serrated knives with a tapered ceramic rod, working each serration individually. Or send them to a professional. -> Most serrated knives stay adequate for years without sharpening. NEVER press hard on the stone. -> More pressure does not equal faster sharpening. It creates uneven wear on the stone and inconsistent results on the blade. -> Let the abrasive do the work. The weight of your hands plus light additional pressure is all you need. NEVER sharpen on a dished (concave) stone. -> A stone that's no longer flat will round your bevel and prevent a clean edge. -> Flatten your stones regularly with a flattening stone or 120-grit wet/dry sandpaper on a piece of flat glass. ``` ## If This Fails - **Can't maintain a consistent angle?** Buy a $5-10 angle guide clip. It attaches to the spine and keeps the angle consistent while you develop the feel. Use it for a month, then try without. - **Edge still dull after sharpening?** Check three things: (a) Are you raising a burr? If not, you're not reaching the edge. Keep going. (b) Are you at the right angle? Use the Sharpie trick to verify. (c) Is your stone flat? Flatten it and try again. - **Knife has chips or major damage?** Start with a coarser stone (400-600 grit) to remove material faster, then progress through 1000 and 6000. Major damage may need professional repair. - **Overwhelmed by all the tools and grits?** Start with one combo stone (1000/6000) and one kitchen knife. Practice until you can consistently pass the paper test. Then expand to other tools. - **Stone is glazed or not cutting?** Your stone is loaded with metal particles. Flatten it with a flattening stone or sandpaper on glass. This also exposes fresh abrasive. ## Rules - Always emphasize that a sharp knife is safer than a dull one. This is counterintuitive to many people and must be stated explicitly. - Match the sharpening method to the tool. Don't recommend whetstone technique for axes or grinding wheels for kitchen knives. - Include the common mistakes for each tool type — these are where most damage happens. - Recommend honing before sharpening. Most people sharpen too often and hone too rarely. - Never recommend pull-through sharpeners as a primary method. They are acceptable as emergency or convenience tools only. ## Tips - A honing rod before each cooking session is the single most impactful thing you can do for your knives. It takes 30 seconds and extends the time between sharpenings from weeks to months. - The Sharpie trick is the best training tool for beginners. Use it every time until you can feel the correct angle without looking. - Buy one good knife and keep it sharp rather than a set of expensive knives you never maintain. A $40 Victorinox Fibrox sharpened properly outperforms a $200 knife that's dull. - Check your whetstone for flatness by laying a ruler across it. If you see daylight under the ruler, flatten the stone before sharpening. - After sharpening, wash the knife with soap and water. Metal particles left on the blade will transfer to food and accelerate corrosion. - If someone offers to sharpen your knives with a bench grinder, politely decline. ## Agent State ```yaml state: assessment: tool_type: null # kitchen_knife, pocket_knife, axe, garden_tool, chisel, scissors blade_steel: null # stainless, carbon, high-carbon_stainless, unknown blade_style: null # japanese, western, serrated, single_bevel current_condition: null # slightly_dull, dull, chipped, damaged, neglected equipment_owned: [] sharpening: technique_taught: false angle_determined: null burr_concept_understood: false sharpie_trick_introduced: false sharpness_tested: false test_result: null # paper_pass, paper_fail, tomato_pass, hair_pass maintenance: honing_frequency: null sharpening_frequency: null stone_last_flattened: null follow_up: next_sharpening_reminder: null ``` ## Automation Triggers ```yaml triggers: - name: tool_identification condition: "assessment.tool_type IS null AND user_asks_about_sharpening" action: "What are you sharpening? Kitchen knives, pocket knife, axe, garden tools, or shop tools? The technique is different for each, and I want to give you the right approach." - name: honing_first condition: "assessment.current_condition == 'slightly_dull' AND assessment.tool_type == 'kitchen_knife'" action: "Before we sharpen, try honing first. If the edge is just rolled (not rounded or chipped), a honing rod will fix it in 30 seconds. Do you have a ceramic or diamond honing rod?" - name: equipment_check condition: "sharpening.technique_taught IS false AND assessment.equipment_owned IS EMPTY" action: "You'll need a combination whetstone, 1000/6000 grit. King, Shapton, or Suehiro are reliable brands, $20-35. And a ceramic honing rod for maintenance between sharpenings, $10-20. That's all you need to start." - name: angle_training condition: "sharpening.technique_taught IS true AND sharpening.sharpie_trick_introduced IS false" action: "Try the Sharpie trick: color the entire edge bevel with a black marker, then make a few strokes. Where the marker was removed shows whether your angle is correct. It's the fastest way to calibrate." - name: maintenance_reminder condition: "sharpening.sharpness_tested IS true AND sharpening.test_result CONTAINS 'pass'" schedule: "90 days after last sharpening" action: "It's been about 3 months since you sharpened your knives. Have you been honing regularly? If the knives are struggling with the paper test again, it's time for another session on the whetstone." ```


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