Steel: "01" vs "A2"

C

Coober

Joined
Sep 11, 2005
Messages
6
Whilst looking to buy a new 'bushcraft' type knife, I've become puzzled by the different steels used on both sides of the Atlantic:

In the UK, many knives use "01" steel, which doesn't seem to feature so much in the USA. Conversely, "A2" steel seems to be used in the USA, but not much in the UK. Examples of this would be the "Ray Mears" knives and the various similar knives that have resulted - most (if not all) of which use 01. Chris Reeve (one-piece) bush knives use A2.

According to some graphs I found on-line, both 01 and A2 have very similar 'toughness' & 'wear resistance' profiles. Some further research suggests that both hold an edge extremely well. From what I've read, the only real difference seems to be that 01 has more of a tendency to rust than A2.

If indeed 01 is prone to rust, it would seem to be an odd choice for a blade that, if used for it's intended purpose, would often be in water or other damp conditions (jungle etc.).

Perhaps someone could point out the virtues/limitations of these two steels.
 
Just a matter of what's available in the market. A2 is not a standard European tool steel, and is thus not commonly available in EUrope. It is a very common tool steel in the US. It's just the way the markets developed historically. Your observations about them are pretty much right on. O1 is a little cheaper, easier to use (machine & grind), and can be heat treated from a lower temperature, if that is a concern. A2 is harder to machine & grind, but will hold an adge a little longer, and be a bit more stain resistant. There probably aren't many knife applications where one couldn't be suitable alternative for the other.
 
A2 is a very common steel in Europe too, for example Uddeholm sells it under the name "Rigor".
 
You'll find O1 here in America. Some Randall knives are made from O1.

Some Custom Knife-Makers favor it since it's easy to work with. But O1 requires quite a bit of care. Otherwise, it'll rust on you like you wouldn't believe.
 
I think it's the 'rust potential' that worries me the most. The most puzzling thing is that in the UK, the most well-known outdoorsman (Ray Mears) highly recommends knives made from 01 and almost all knives of a similar design ("Woodlore") are made in 01. If rusting were such an issue, surely this would have been mentioned somewhere (even if only how to maintain the blade to prevent rusting).
 
Coober said:
I think it's the 'rust potential' that worries me the most. The most puzzling thing is that in the UK, the most well-known outdoorsman (Ray Mears) highly recommends knives made from 01 and almost all knives of a similar design ("Woodlore") are made in 01. If rusting were such an issue, surely this would have been mentioned somewhere (even if only how to maintain the blade to prevent rusting).
Click to expand...

Rusting definitely is an issue with O1. Aside from that, it's an excellent steel for use in knife blades. But it requires a lot of care.... more so than other types of steels. Some don't consider it to be a huge disadvantage.
 
You have to decide on how important the rust issue actually is to you, and weigh cosmetics versus function. An absolutely WONDERFUL example that was brought up recently in another thread (if the author reads this, please claim it) was that the Titanic--a gigantic chunk of non-stainless steel--has been sitting in saltwater for 95 years now and is still there, and recognizeably a ship. Mariners went to sea for hundreds of years with simple iron and steel tools that must have stayed useable for their intended applications or they never would have stopped using bronze.

I'm not saying that you should purposely let your knife rust; nor that you'd be wrong to want to protect your investment. Just keep in mind that if it develops some surface rust, it doesn't mean that it has become "ruined" by any stretch, unless you're planning to keep it as a pristine piece of art rather than a tool. The leaf springs that have been holding the back of my truck up for 22 years now are completely covered in rust and none the worse for it.

In the case of a knife, what you want to ensure is that you keep the edge dry and relatively clean in between uses, so as to slow the dulling effects that corrosion will have on it, but that is easily done. I like carrying a little tube of chapstick with me to use on non-stainless edges. When you're finished with what you're doing, wipe the edge clean and then pull it through the wax and it'll be coated well enough to offer some protection.

Poorly done A2 will be easily outclassed by well done O1, and vice versa--the type of steel used on its own doesn't make or break the knife. The best thing to do when picking your steel is to ask the maker you're talking to what they are most comfortable working with, especially if they are doing their own heat treatment. If he/she has made 100 knives out of O1 and gave A2 a try once or twice in the last decade, go with the O1. For another example; I am fairly good at metalworking, while my father can do marvelous things with wood. Both of us understand the basics of working with either material, but knowing the basics and turning out superior products are not the same thing. :D

With proper heat treatment and blade/edge geometry for the tasks you want the knife to do, either steel will serve you very well.
 
t1mpani pretty much summed it up with his post. Either steel is a good choice. Just because O1 may get wet, doesn't mean it will immediately rust. Just try to keep it as dry as possible. Keep oil on it when stored away. A2 will rust also if left wet. I rate both as top steels for outdoor use blades. Both are tough, take a fine edge and hold it well.
Scott
 
The choice between O1 and A2 wouldn't be because of availability. O1 and A2 are part of what I call the "big three" tool steels: A2, D2, and O1. They are literally everywhere. There is a possibility that a large manufacturer could get O1 for a lower cost than A2, but A2 would be easier to heat treat for a manufacturer to heat treat because it is air hardening. When it comes to custom knives, O1 is fairly popular among forgers but A2 hasn't become popular with a whole lot of stock removal makers, though there are some who use it.
 
I've used both and find that their properties are extremely similar. Rust resistance are extremely similar. Not a big deal as it can be removed with simichrome.

I like the edge I can get with O1 better and it seems tougher in chopping (when both are hardened to HRC 60).

A lot of people call O1 a "beginner's steel" -but take a look at what the ABS guys can do with it at cutting competitions. It really is that good if you know what you're doing.

A2 is also easier to heat treat.
 
Isn't the Mccann Industries, whatzit auto that uses a cylinder with nitrogen, instead of a spring, made with O1?
 
Guess I'm pretty taken with the 'Woodlore' type that use 01.

My only remaining question therefore is to ask if there is any advice for keeping it as rust-free as possible. Naturally keeping it dry where possible, but as it will undoubtedly be used for food-prep, I'm a bit concerned about what coatings can be applied in this regard.
 
Coober said:
Guess I'm pretty taken with the 'Woodlore' type that use 01.

My only remaining question therefore is to ask if there is any advice for keeping it as rust-free as possible. Naturally keeping it dry where possible, but as it will undoubtedly be used for food-prep, I'm a bit concerned about what coatings can be applied in this regard.
Click to expand...

For food prep, keep a light coating of sunflower oil on the blade. This will protect it from rust, but also allow you to wipe off the oil and immediately use it on foods.
 
Yes, one is air and the other oil hardening. I have detailed materials data on the site.

-Cliff
 
When dealing with rust, a lot depends on your environment and usage. I live in dry Colorado, and even high carbon steels 10XX and tool steels don't rust here unless you really mistreat them. I store all of my knives in their sheaths, whether it's leather or kydex, and have never had a knife start spotting or rusting in it's sheath yet. Some I've stored this way since 1985. All I do is keep them dry, only oil them if I'm going camping.

Cape town might be a little more moist, but in a dry climate, it's really a non-issue.
 
mr.trooper said:
The chemical formulas iv seen for O1 and A2 are almost identical. Are they really that different?
Click to expand...


From http://www.ajh-knives.com/metals.html

Alloy________________O-1_________A2
Carbon______________0.9__________1
Manganese__________1.2__________0.6
Chromium___________0.5__________5.25
Tungsten____________0.5___________--
Vanadium___________0.2__________0.25
Molybdenum_________--___________1.1

​
 
What I've read is that because O1 has less chromium(which makes the knife more resistant to rust) than A2 it forms much smaller carbides while going through heat treatment which allows it to be sharpened to a keener edge more easily but it dulls a little faster.

This article was very helpful:

http://thewoodwhisperer.com/a2-vs-o1-tool-steel/
 
COOBER: Had to decide between O1 and A2 when ordering my Skookum Bush Tool. The maker's webpage mentioned it was easier to get a spark off a firesteel and an O1 blade + easier to sharpen. Knives don't rust too much when you use them. They really rust quickly when they are unloved in the back of a drawer, unoiled.
 
Monocrom said:
Rusting definitely is an issue with O1. Aside from that, it's an excellent steel for use in knife blades. But it requires a lot of care.... more so than other types of steels. Some don't consider it to be a huge disadvantage.
Click to expand...

Okay, I primarily use this knife for kitchen duty. It is made of O1. I don't oil it or anything, I simply give it a rinse in the sink after use and wipe dry then pop it into the block. Often times the knife sits there in the acidic juices of foods during food preparation. It rapidly develops a patina and that prevents rust. Every once in a while I want it shiny again so I'll use flitz polish or just sand it with 2000 grit. After a couple of weeks of use it gets that flat grey, blotchy patina again.

It never rusts on me. I know that salt air environments are more of a problem, but even when I was working in an ocean environment and using a 1095 blade as a boat knife, I just forced a patina on it with a lemon and it kept all the corrosion at bay. The whole corrosion thing is really only a deal if you want to keep your knife shiny all the time.

DSC_0017-13.jpg


Here is the same blade shiny

DSC_0070-7.jpg


Here is the patina of a 15N20 blade after I used it to cut up and process (removing the skins) 120 lbs of tomatoes for canning. Tomato juice is very acidic. I actually love how even a patina that produced!

DSC_0069-14.jpg


With respect to corrosion resistance, I think you are either - scared to hell of any corrosion and thus you should go the stainless route or maybe even one of those Nitrogen based steels like spyderco uses in the aquasalts, or you should just grin and bear it and go tool steel/carbon. I don't think you'll find such a difference in the relative corrosion resistance between A2 and O1 to make it a real deciding factor. If the environment and conditions are tough enough to spot O1, they will also do so for A1 after just a little more time.
 
You must log in or register to reply here.
Back
Top