O1 is an oil-hardening tool steel that has long been popular with custom makers and bushcraft knife brands.
O1 Steel at a Glance
| Type | Tool steel |
|---|---|
| Made by | Many mills (AISI O1 oil-hardening tool steel) |
| Typical hardness | 58-62 HRC |
| Key elements | Carbon about 0.95%, manganese about 1.2%, chromium about 0.5%, tungsten about 0.5%, vanadium about 0.2% |
| Edge retention | 4/10 (modest) |
| Toughness | 6/10 (good) |
| Rust resistance | 1/10 (low) |
| Ease of sharpening | 8/10 (easy) |
| Best for | Bushcraft and custom |
Ratings are relative 1 to 10 scores for typical factory heat treatments. See how O1 ranks against 46 other steels in our Knife Steel Chart.
What Is O1 Steel?
O1 hardens in oil, which makes heat treatment more forgiving than water-hardening steels. Tungsten adds a little wear resistance.
O1 Steel Properties
- Edge retention: Modest.
- Toughness: Good.
- Rust resistance: Low. Keep it dry and lightly oiled.
- Ease of sharpening: Easy.
O1 vs Other Steels
O1 vs 1095
Compared with 1095, O1 holds an edge slightly longer. 1095 is slightly easier to sharpen. Read our 1095 guide.
O1 vs 52100
Compared with O1, 52100 is slightly tougher. Read our 52100 guide.
O1 vs D2
Compared with D2, O1 is tougher and is easier to sharpen. D2 holds an edge longer and resists rust better. Read our D2 guide.
Is O1 Steel Good for Knives?
Yes, for bushcraft, carving and custom knives.
Pros:
- Takes a very fine edge
- Easy to sharpen
- Decent toughness
Cons:
- Rusts easily
Knives That Use O1 Steel
Makers sometimes change blade steels between versions, so check the listing to confirm the steel before you buy.
Frequently Asked Questions
Is O1 steel stainless?
No. O1 is not stainless and will rust or patina if left wet. Keep it dry and lightly oiled.
How hard is O1 steel?
Knives in O1 are usually heat treated to around 58-62 HRC.
Is O1 easy to sharpen?
Easy. Most standard stones and pull-through sharpeners work.