sharpen-knife

name	sharpen-knife
locale	wenyan-lite
source_locale	en
source_commit	82c77053
translator	Julius Brussee homage — caveman
translation_date	2026-05-03
description	Sharpen and maintain knives using whetstones, field stones, and improvised abrasives. Covers blade anatomy, bevel assessment, whetstone technique (coarse to fine progression), stropping, sharpness testing, field sharpening methods, and ongoing edge maintenance. Use when a knife fails the fingernail test, when cutting tasks require excessive pressure, before a trip where a sharp blade is essential, after heavy use, or when a blade has visible nicks or a rolled edge. Applicable to bushcraft blades, folding knives, and garden cutting tools.
license	MIT
allowed-tools	Read
metadata	{"author":"Philipp Thoss","version":"1.0","domain":"bushcraft","complexity":"intermediate","language":"natural","tags":"bushcraft, knife, sharpening, blade, maintenance, whetstone, tools, gardening"}

磨刀

以磨刀石、皮帶條與野外權宜法磨利並維護刀刃。

適用時機

• 刀刃輕劃指甲不能掛住
• 切割任務需過大壓力或產生粗糙切口
• 出行或執行需鋒利刀刃之任務前（雕刻、處理食物、劈柴）
• 重度使用後之例行維護（依使用情況每 1-3 個野外日）
• 刀刃出現可見之缺口、崩裂或捲邊

輸入

• 必要：待磨之刀
• 必要：磨蝕表面（磨刀石、鑽石板、陶瓷棒或野外石塊）
• 選擇性：皮帶條（皮帶、紙板或光滑木材）配合磨膏
• 選擇性：角度導引或錢幣供斜面參考
• 選擇性：簽字筆（Sharpie）供斜面視覺化
• 選擇性：磨刀油或水（依石材類型）

步驟

步驟一：評估刀刃

審視刀以確定所需磨利程度。

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.

預期： 已知刀刃狀況及所需粒度。

失敗時： 若不確定，從中粒（1000）開始。隨後可進一步細化，但對近乎鋒利之刀以過粗開始將去除多餘金屬。

步驟二：認識磨蝕材料

為任務擇選正確之石材。

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                  │
└──────────────┴────────────────┴──────────────────────────────────┘

預期： 已選妥磨蝕材料並備好（依需浸泡、上油或潤濕）。

失敗時： 若無正規磨石可用，陶瓷馬克杯底（未上釉之圈）可作細粒應急磨刀器。汽車車窗底邊功能類似。野外時，光滑河石勝於無物。

步驟三：找出並匹配斜面角

斜面角決定刀刃幾何。除非重塑刀刃輪廓，否則匹配既有角度。

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)

預期： 能以一致之角度持刀，與既有斜面相符。

失敗時： 若徒手無法保持一致角度，使用磨刀導引或夾具系統。角度不一致為磨刀效果不佳之最常見原因。在貴重刀上動手前先以廉價刀練習。

步驟四：磨刀——由粗至細遞進

依所需從最粗至最細逐級磨製。

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

預期： 經最細石材後，刀刃可穩固掛住指甲且能俐落切紙（皮磨前略有拖滯尚可）。

失敗時： 若 20 餘下後仍未起毛邊，檢查角度——可能太陡（在刀刃上方研磨）或太淺（研磨刀身平面）。再用簽字筆法。若石材已釉化（積金屬粉），沖洗並以名倉石或整平板擦拭。

步驟五：以皮帶條磨光

皮磨可去除最後之毛邊，並對齊刀刃至剃刀般之鋒利。

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

預期： 刀刃可削斷臂毛、俐落切如電話簿般薄之紙，或憑自身重量滑過番茄。

失敗時： 若刀感覺鋒利卻仍掛或拖滯，可能某側仍有毛邊。於細石上再做 5 下交替單擊，再皮磨。若刀刃仍不一致，可能某側角度略異——以簽字筆標記並修正。

步驟六：測試鋒利度

以遞進測試衡量刀刃品質。

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

預期： 刀刃通過符合預期用途之鋒利度測試。

失敗時： 若指甲測試通過而紙測試不過，需於細石上多花時間並加強皮磨。若連指甲測試都不過，回到中粒，自步驟四重新磨製。

步驟七：野外磨刀（荒野方法）

當無正規石材可用時。

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.

預期： 刀刃恢復至足以勝任營地任務之功能性鋒利度。

失敗時： 若無合適磨蝕材料可尋，將細沙揉入紋理之硬木平面可作粗糙磨刀面。優先使刀刃可用，而非完美。

步驟八：維護刀刃

預防勝於修復。

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      │
└───────────────────┴────────────────────────────────────────┘

預期： 維護常規可使刀刃於完整磨刀之間保持鋒利。

失敗時： 若發現自身頻繁需要由粗至細之全套磨製，要麼鋼材對任務過軟（考慮較硬之刀），要麼刀刃因誤用而受損（在硬面上切割、橫向扭力、腐蝕）。

驗證

• 選擇粒度遞進前已評估刀刃狀況
• 已識別正確斜面角並一致保持
• 每一粒度階段皆於兩側起毛邊並去除
• 最後石材後已皮磨刀刃
• 刀刃通過符合預期用途之鋒利度測試
• 磨刀後已清潔、擦乾並上油
• 已建立維護常規（用前皮磨）

常見陷阱

• 角度不一致：磨刀失敗最單一常見之因。中途變角將圓化刀刃而非磨利。以簽字筆法驗證，並先練習緩慢、刻意之動作再求速度
• 壓力過大：用力按並不能加快磨利——徒在石上挖出溝痕並可能崩刃。讓磨蝕材料切削；中等壓力即可
• 跳粒度：自 400 直跳 6000 留下細石無法去除之深劃痕。每一粒度應抹除前一粒度之劃痕
• 未起毛邊：若兩側皆形成毛邊前即進入下一粒度，未達頂端則刀不利。耐心——毛邊為檢查點
• 以刀刃方向皮磨：將刀刃推入皮帶條切斷皮革並使刀刃向後折。皮磨務必刀背先行（將刀刃向後拖）
• 忽略單斜面刀之背側：日式單斜面刀僅於斜面側磨，但平背仍需數下輕擊去除毛邊。勿於平面側磨出斜面
• 使用錯誤之石材潤滑劑：水石用水。油石用磨刀油。混用堵塞石材。切勿於油石用水或於水石用油

相關技能

• make-fire — 鋒利之刀對處理火絨、引火柴與羽絨柴至關重要；生火與刀具維護為配套技能
• forage-plants — 鋒利刀刃可實現乾淨、可持續之採收切口，將植物損傷減至最低
• maintain-hand-tools — 園藝刀刃（hori-hori、修枝剪）遵循相似磨刀原則；本技能提供更深入之刀具專屬技巧