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sharpen-knife

pjt222
Updated 6 days ago
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About

This skill provides instructions for sharpening and maintaining knives using whetstones and other abrasives. It covers techniques from basic whetstone progression to field sharpening and edge assessment. Use it when a knife is dull, damaged, or before tasks requiring a sharp blade.

Quick Install

Claude Code

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npx skills add pjt222/agent-almanac -a claude-code
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/plugin add https://github.com/pjt222/agent-almanac
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git clone https://github.com/pjt222/agent-almanac.git ~/.claude/skills/sharpen-knife

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Documentation

礪刃

以礪、皮、權法養刃也。

  • 刃過甲不噬→用
  • 切需重壓或裂→用
  • 出行前需利刃(雕、炊、劈)→用
  • 重用後常養(每 1-3 野日)→用
  • 刃見缺、卷→用

  • :待礪之刃
  • :礪面(礪石、金剛板、瓷棒、野石)
  • :皮(革帶、紙板、滑木)與膏
  • :角規或錢以參斜
  • :墨筆(Sharpie)以顯斜
  • :磨油或水(依石)

一:察刃

驗以定礪級。

Blade Assessment:
┌─────────────────────┬──────────────────────────────────┬─────────────────────┐
│ Condition           │ Signs                            │ Action Needed       │
├─────────────────────┼──────────────────────────────────┼─────────────────────┤
│ Dull (most common)  │ Won't catch on fingernail;       │ Medium grit → fine  │
│                     │ slides off tomato skin;          │ grit → strop        │
│                     │ reflects light along edge        │                     │
├─────────────────────┼──────────────────────────────────┼─────────────────────┤
│ Very dull / abused  │ Visible flat spot along edge;    │ Coarse grit →       │
│                     │ tears rather than cuts;          │ medium → fine →     │
│                     │ edge shines under light          │ strop               │
├─────────────────────┼──────────────────────────────────┼─────────────────────┤
│ Nicked / chipped    │ Visible notches in edge;         │ Coarse grit to      │
│                     │ snags on material when drawing   │ grind past nicks →  │
│                     │ across                           │ reprofile → strop   │
├─────────────────────┼──────────────────────────────────┼─────────────────────┤
│ Slightly dull       │ Catches on fingernail but not    │ Strop only (or a    │
│ (maintenance)       │ crisply; still cuts paper but    │ few passes on fine  │
│                     │ not cleanly                      │ grit then strop)    │
├─────────────────────┼──────────────────────────────────┼─────────────────────┤
│ Rolled edge         │ Edge feels sharp on one side     │ Strop firmly on     │
│                     │ but dull on the other; blade     │ both sides; if that │
│                     │ curves microscopically           │ fails, light passes │
│                     │                                  │ on fine stone       │
└─────────────────────┴──────────────────────────────────┴─────────────────────┘

Light Test:
Hold the blade edge-on under a bright light. A sharp edge is invisible —
it has no width. A dull edge reflects a thin line of light where metal
has folded or flattened.

得:知刃況及所需粒。

敗:未明→始於中粒(1000)。可後細之。始過粗則白損鐵。

二:知礪

擇宜石。

Abrasive Types:
┌─────────────────────┬─────────────────────────────────┬──────────────────────┐
│ Type                │ Characteristics                 │ Best For             │
├─────────────────────┼─────────────────────────────────┼──────────────────────┤
│ Water stones        │ Soak 5-15 min before use;       │ Home sharpening;     │
│ (natural/synthetic) │ fast cutting; wear quickly;      │ best feedback and    │
│                     │ need flattening periodically     │ finest edges         │
├─────────────────────┼─────────────────────────────────┼──────────────────────┤
│ Diamond plates      │ No soaking needed (use water    │ Field use; hard      │
│                     │ as lubricant); very durable;     │ steels; flattening   │
│                     │ aggressive cut                   │ water stones         │
├─────────────────────┼─────────────────────────────────┼──────────────────────┤
│ Ceramic stones/rods │ No soaking; very fine grit;     │ Touch-up and         │
│                     │ hard and slow-wearing            │ maintenance; field   │
│                     │                                  │ carry                │
├─────────────────────┼─────────────────────────────────┼──────────────────────┤
│ Oil stones          │ Use honing oil; slower cutting;  │ Traditional;         │
│ (Arkansas, India)   │ very durable; less messy         │ workshop use         │
├─────────────────────┼─────────────────────────────────┼──────────────────────┤
│ Field stones        │ Any smooth, fine-grained stone;  │ Wilderness emergency │
│ (improvised)        │ river stones, slate, sandstone;  │ when no other       │
│                     │ unpredictable grit               │ abrasive available   │
└─────────────────────┴─────────────────────────────────┴──────────────────────┘

Grit Progression:
┌──────────────┬────────────────┬──────────────────────────────────┐
│ Grit Range   │ Purpose        │ When to Use                      │
├──────────────┼────────────────┼──────────────────────────────────┤
│ 220-400      │ Coarse         │ Reprofiling, removing chips,     │
│              │                │ establishing a new bevel         │
├──────────────┼────────────────┼──────────────────────────────────┤
│ 800-1000     │ Medium         │ Standard sharpening of a dull    │
│              │                │ blade; the workhorse grit        │
├──────────────┼────────────────┼──────────────────────────────────┤
│ 3000-6000    │ Fine           │ Refining the edge after medium;  │
│              │                │ polishing the bevel              │
├──────────────┼────────────────┼──────────────────────────────────┤
│ 8000+        │ Ultra-fine     │ Mirror polish; razors; optional  │
│              │                │ for most knives                  │
└──────────────┴────────────────┴──────────────────────────────────┘

得:擇正石備(浸、油、潤)。

敗:無正石→瓷杯底(無釉環)為細粒急用。車窗邊亦同。野→滑河石勝無。

三:覓配斜

斜定刃幾何。配既存之斜,除非重塑。

Common Bevel Angles:
┌─────────────────────┬───────────────┬──────────────────────────────┐
│ Knife Type          │ Angle (per    │ Notes                        │
│                     │ side)         │                              │
├─────────────────────┼───────────────┼──────────────────────────────┤
│ Bushcraft / fixed   │ 20-25°        │ Balance of sharpness and     │
│ blade               │               │ durability for wood, rope,   │
│                     │               │ and general camp tasks       │
├─────────────────────┼───────────────┼──────────────────────────────┤
│ Kitchen knife       │ 15-20°        │ Thinner for clean food cuts; │
│                     │               │ less durable on hard items   │
├─────────────────────┼───────────────┼──────────────────────────────┤
│ Japanese kitchen    │ 10-15°        │ Very acute; exceptional      │
│                     │               │ sharpness; fragile on bone   │
├─────────────────────┼───────────────┼──────────────────────────────┤
│ Machete / chopper   │ 25-30°        │ Thick for impact resistance  │
├─────────────────────┼───────────────┼──────────────────────────────┤
│ Folding knife (EDC) │ 20°           │ General purpose              │
├─────────────────────┼───────────────┼──────────────────────────────┤
│ Hori-hori / garden  │ 15-20°        │ Similar to kitchen; for soil │
│ blade               │               │ and root cutting             │
└─────────────────────┴───────────────┴──────────────────────────────┘

Finding the Angle:
1. Lay the blade flat on the stone (0°)
2. Slowly raise the spine until the bevel sits flush on the stone
3. The point where the entire bevel contacts the stone is the correct angle
4. Marker trick: color the bevel with a Sharpie, make one stroke on the stone.
   - Ink removed from the whole bevel = correct angle
   - Ink removed only at the edge = angle too high
   - Ink removed only at the shoulder = angle too low

Coin Stack Reference (for consistent angle):
- 1 coin under spine ≈ 12-15° (thin kitchen knives)
- 2 coins under spine ≈ 17-20° (general purpose)
- 3 coins under spine ≈ 22-25° (bushcraft / heavy use)
(Varies with blade width — wider blades need more coins for the same angle)

得:可恆持配斜之角。

敗:徒手不恆→用導或夾。角不恆乃礪敗最常因。先於賤刃試。

四:礪——粗至細進

由所需最粗至最細逐粒。

Sharpening Technique:

SETUP:
1. Place stone on a stable, non-slip surface (wet towel underneath)
2. Ensure the stone is fully saturated (water stones) or oiled (oil stones)
3. Position yourself so you can make smooth, controlled strokes

STROKE METHOD (per side):
1. Place the blade on the stone at the correct angle
2. Push the edge forward along the stone as if slicing a thin layer off
   the surface — from heel to tip in a sweeping arc
3. Maintain consistent pressure and angle throughout the stroke
4. Light to moderate pressure — let the abrasive do the work
5. 5-10 strokes per side, then alternate

ALTERNATING PATTERN:
- 5-10 strokes on side A → 5-10 strokes on side B → repeat
- As you approach a sharp edge, reduce to 3 strokes per side,
  then 1 stroke per side (alternating single strokes)

CHECKING FOR A BURR:
- After sufficient strokes on one side, a thin wire edge (burr)
  forms on the opposite side
- Feel for it: drag your thumb ACROSS the edge (never along it)
  from the spine toward the edge — the burr catches slightly
  on the side opposite to the one you were sharpening
- A burr means you have reached the apex — move to the other side
- Once both sides have raised and removed the burr, move to the
  next finer grit

PROGRESSION:
Coarse (if needed) → raise burr on both sides → move to medium
Medium → raise burr on both sides → move to fine
Fine → light alternating strokes → strop

得:最細石後,刃緊噬甲、利切紙(皮前少滯可)。

敗:20+ 擊不起芒→驗角。或過陡(磨刃上)或過淺(磨刃面)。再用墨筆。石蔽(鐵屑塞)→沖之、以那古拉石或平板擦。

五:皮刃

皮去末芒、整刃至剃利。

Stropping Protocol:
1. Use a leather strop, smooth cardboard, or bare softwood (palm side
   of a leather belt works in the field)
2. Apply stropping compound if available (chromium oxide / green compound,
   or fine polishing paste)
3. Lay the blade flat at the sharpening angle
4. Draw the blade SPINE-FIRST (opposite direction to sharpening —
   you are dragging the edge backward, not pushing it forward)
5. Light pressure only — less than sharpening
6. Alternate sides: 5 strokes per side → 3 → 1 → 1 → 1
7. Total: 20-30 strokes alternating

⚠️ CRITICAL: Strop spine-first (pull the edge backward).
   Pushing edge-first into a strop cuts the leather and
   dulls the blade.

Field Strop Alternatives:
- Smooth side of a leather belt (hold taut)
- Cardboard or newspaper laid flat
- Palm of your hand (careful! very light pressure, spine-first only)
- Smooth driftwood or the flat of a dry log

得:刃斷臂毛、利切薄紙、自重穿熟番茄。

敗:似利而滯→一面或留芒。再 5 細石單擊、後皮。仍不勻→一側或角異——墨筆糾之。

六:驗利

漸進測以察刃質。

Sharpness Tests (from easiest to most demanding):

1. FINGERNAIL TEST (basic):
   Lightly draw the edge across a fingernail at 45°.
   Sharp: catches and digs in immediately
   Dull: slides across without catching

2. PAPER TEST (good):
   Hold a sheet of printer paper by one edge and slice downward.
   Sharp: cuts cleanly with no tearing
   Acceptable: cuts with slight drag
   Dull: tears, folds, or won't start a cut

3. TOMATO TEST (kitchen standard):
   Place a ripe tomato on a cutting board.
   Sharp: the weight of the blade alone starts the cut
   Dull: requires downward pressure to break the skin

4. ARM HAIR TEST (very sharp):
   Lightly draw the blade across arm hair without touching skin.
   Sharp: hair pops cleanly
   Not quite: hair bends or pushes aside

5. HANGING HAIR TEST (razor sharp):
   Hold a single hair and bring the blade to it.
   Razor: cuts the hair with minimal pressure
   This level is unnecessary for most bushcraft/garden use.

Sharpness Standards by Use:
- Bushcraft / camp knife: pass paper test cleanly → good to go
- Kitchen knife: pass tomato test → good to go
- Carving knife: pass arm hair test → ideal
- Garden blade (hori-hori): pass paper test → sufficient

得:刃過合用之測。

敗:過甲而敗紙→需細石更久、皮更多。全敗甲→歸中粒、自步四再礪。

七:野礪(荒野法)

無正石時。

Field Expedient Sharpening:

RIVER STONES:
1. Find a smooth, flat, fine-grained stone (slate, granite, basalt)
2. Wet the surface
3. Use the same technique as Step 4 — angle, stroke, alternate
4. Won't produce a polished edge but will restore cutting ability
5. Look for stones with a slightly gritty feel — glassy smooth
   stones won't cut fast enough

CERAMIC:
- Bottom of a ceramic mug (unglazed ring) serves as a fine hone
- Excellent for maintenance touch-ups in camp

CAR WINDOW EDGE:
- The edge of a car window (rolled down slightly) is fine-grit ceramic
- 5-10 strokes per side for a quick field touch-up

SANDPAPER ON FLAT SURFACE:
- If you have sandpaper (any grit), place it on a flat log or rock
- Sharpen as you would on a stone
- Works surprisingly well

LEATHER BELT STROP:
- Always available in the field if wearing a belt
- Hold taut between hand and fixed point
- Strop spine-first after any field sharpening

Minimum Field Sharpening Kit (recommended carry):
- Small diamond plate (credit-card size) or ceramic rod
- Leather strop strip (10cm x 3cm, fits in sheath)
These two items weigh almost nothing and handle all field needs.

得:刃復可用之利、足野務。

敗:無宜礪→平硬木鋪細沙入紋、可權作礪面。求功而後求美。

八:護刃

防勝於復。

Edge Maintenance Habits:
1. Strop before each use — 10 strokes per side on leather or cardboard
   (this alone can keep a knife sharp for weeks between stone sessions)
2. Cut on wood, not stone, glass, ceramic, or metal surfaces
3. Never pry, twist, or use the edge as a screwdriver
4. Clean and dry the blade after use — moisture causes corrosion,
   and corrosion eats the fine edge
5. Store knives in sheaths, on magnetic strips, or in blade guards —
   never loose in a drawer where edges contact other metal
6. Carbon steel: oil the blade after cleaning (camellia oil, mineral oil)
7. Stainless steel: less maintenance, but still benefits from drying
   and occasional oiling

Sharpening Frequency:
┌───────────────────┬────────────────────────────────────────┐
│ Use Pattern        │ Recommended Frequency                  │
├───────────────────┼────────────────────────────────────────┤
│ Daily kitchen use  │ Strop daily; stone weekly              │
│ Weekend bushcraft  │ Strop before each trip; stone monthly  │
│ Occasional garden  │ Strop before use; stone seasonally     │
│ Heavy field use    │ Strop daily; stone every 2-3 days      │
└───────────────────┴────────────────────────────────────────┘

得:常養之法、刃於石間期亦利。

敗:屢需全粗至細礪→或鐵過軟(換硬刃)、或刃為誤用所傷(切硬面、橫扭、銹)。

  • 擇粒前察刃況
  • 識正斜而恆持
  • 各粒皆兩面起芒去芒
  • 末石後皮刃
  • 刃過合用之利測
  • 礪後潔、乾、油
  • 養法(用前皮)已立

  • 角不恆:礪敗第一因。擊中變角→圓刃非利。墨筆驗、慢練乃增速
  • 壓過重:重壓不增速——刨石、缺刃。任礪自切;中壓足
  • 跳粒:400 直至 6000 留深痕、細石不能除。每粒當去前痕
  • 不起芒:未兩面起芒而進次粒→未達峰、刃不利。耐之——芒為證
  • 皮刃前向:推刃入皮割革、卷刃。必脊先(拖刃後)
  • 忽單斜背:和式單斜唯礪斜面,平背仍需輕擊去芒。勿於平面建斜
  • 誤用石潤:水石用水、油石用油。混則塞石。永勿水於油石或油於水石

  • make-fire — 利刃為理絨、枝、羽棍所必,火與刃同養
  • forage-plants — 利刃可清、續、傷草最少之收
  • maintain-hand-tools — 園刃(hori-hori、剪)礪法同,此技深於刃

GitHub Repository

pjt222/agent-almanac
Path: i18n/wenyan-ultra/skills/sharpen-knife
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