Steel matchup
8670 and 5160, compared on the five things that decide a blade: toughness, edge retention, corrosion, heat treat and how each one grinds.
Band-saw steel turned knife steel: ~0.70% carbon with a nickel addition that buys elite impact toughness at working hardness, a cheap price per bar, and one of the most forgiving heat treats in the shop. Low wear resistance is the honest tradeoff — this is a chopper's steel, not a slicer's.
The classic chromium spring steel: outstanding toughness at moderate hardness, low cost, and a leaf-spring heritage that makes it the default choice for swords, machetes and camp choppers — provided you resist the urge to run it hard.
Dimension by dimension
Each steel's own note, its score out of five, and what separates the two in that one column. The higher score in a row is marked in purple.
| Dimension | 8670 | 5160 | What separates them |
|---|---|---|---|
| Toughness | The reason to buy it. Measured at roughly 27–50 ft-lbs around 59–60 HRC (Knife Steel Nerds — batch and machining dependent), which only the 5160/15N20 class matches among common knife steels. The nickel lets it keep that toughness at a hardness where 5160 is usually run softer. | The whole reason to choose it. Low carbon content means very little excess carbide, and the chromium and manganese give clean, deep hardening — the result is a steel that bends, absorbs impact and returns rather than chipping or snapping. This is why it dominates sword and chopper work. Critically, the advantage lives at 57–59 HRC and is largely spent by 61 HRC. | A statistical tie at the top of the charts — this pairing is the 1a/1b of budget toughness. The practical difference: 5160 is traditionally run softer (56–58 HRC) where it is nearly indestructible, while 8670's nickel lets it keep elite toughness at 59–60. Same class, different sweet spots. |
| Edge retention | Low wear resistance and no vanadium carbides — a fine-grained edge that takes a keen apex, dulls faster than any alloyed steel, and comes back with a few passes on a cheap stone. For its intended hard-use knives that fast maintenance loop is a feature, not a flaw. | Modest, and honestly so. At roughly 0.60% carbon there is neither the hardness nor the carbide volume for long slicing life — it will need touching up sooner than 1084, O1 or 52100. In exchange it sharpens back to working sharp in a few passes on almost any stone, which is the right tradeoff for a field blade. | 8670 slightly, mostly because it is comfortable a point or two harder — at equal hardness there is little between them, and both are low-wear steels that trade endurance for easy field sharpening. |
| Corrosion resistance | Carbon-steel rust behavior; the sub-1% nickel does not meaningfully slow it (15N20 carries twice the nickel and still only manages a shade better). Oil it, dry it, patina it. | None to speak of. The ~0.8% chromium is a hardenability alloy, not a stainless one. Expect rust on neglected blades and a fast patina on working ones — for a machete or camp knife that patina is a perfectly good protective finish. | Both rust readily; neither alloy addition helps meaningfully. Spring steel patina stories and band-saw rust stories are the same story. Oil, dry, repeat. |
| Heat treat | Austenitize 1500°F, 10–15 min soak (1475–1550°F window; avoid 1450°F and 1600°F+). Parks 50 or AAA both reach full hardness. Temper 2×2h anywhere in 300–450°F — hardness/toughness trade is linear with no tempered-martensite embrittlement in that range. ~58–60 HRC at a 400°F temper; forge heat treating works well thanks to decent hardenability. | Normalize and thermal cycle first, especially for forged blades or reclaimed spring stock. Austenitize at ~1525°F with a 10 minute soak, quench in a medium-fast oil — the chromium provides enough hardenability that a violent quench is unnecessary, which helps long blades survive straight. Temper twice for two hours at 400–450°F to land 57–59 HRC. Resist going higher: above about 60 HRC you trade away the toughness that is 5160's entire reason for existing. | Both are forge-friendly, deep-enough-hardening steels with wide margins. 5160's chromium wants a decent soak to do its job — rushed forge cycles leave performance on the table more often than people admit. 8670's tested 1500°F recipe with its linear no-trap temper range is about as foolproof as heat treating gets. Slight nod to 8670 for predictability. |
| Grinding | A pleasure. Annealed 8670 grinds, drills and files like the band-saw stock it is, forges smoothly, and its thin common bar sizes (often ~0.080–0.125 inch) mean less hogging to start with. Belts last, files bite, nothing tears. | Grinds and files easily in the annealed state and forges beautifully, which is why it is a bladesmithing staple. Hardened 5160 at 57–59 HRC is also comparatively cooperative on the belt. New bar stock behaves far better than reclaimed leaf springs, which arrive with scale, service fatigue and unknown history. | No meaningful difference on the belt — both grind cleanly and quickly with cheap ceramics. Stock is the real difference: 5160 runs thick (spring heritage) and suits big-blade builds; 8670 runs thin and saves grinding time on knife-sized work. |
Best use
8670
camp knives and choppers at knife scale, batoning blades run slightly harder, budget builds where thin stock and low price move the decision.
Open the 8670 reference5160
swords, large choppers, tomahawks, anything with spring flex in the design brief, traditional forged big blades.
Open the 5160 reference
The long answer
These two sit at the very top of the common-steel toughness charts, close enough that testing struggles to separate them. 5160 earned its reputation in leaf springs and swords; 8670 earned its in band-saw blades that flex millions of cycles without cracking. The choice usually comes down to hardness targets and what your supplier actually stocks.
Keep comparing
Keep reading
5160 is a forgiving steel on the grinder, and the challenges it does present come from the blades people make out of it rather than the alloy itself…
8670 might be the most cooperative steel a 2×72 ever meets. It arrives thin, grinds clean, tolerates heat-treat improvisation, and sharpens on anything…
Every knife steel is iron plus a specific recipe of other elements, and each of those elements pulls the steel’s behavior in a particular direction…
Same bench
Whichever steel wins, the grind is only as flat as the platen behind it. I machine the parts, hand-assemble, track and test Torus grinders in Sterling, Illinois.
Current dual-axis platform with a fiber-laser-cut 6061 chassis and single-knob tracking.
Current dual-axis platform with a steel chassis, more mass and less vibration.
Prior-design aluminum chassis, 90-degree tilt and 1.5-inch tooling arms.
One-man shop
Tell me what the blade is for and how you heat treat, and I will tell you which of these I would put on the bench — including when the answer is neither.
