Practical differences between four common steels

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Brian.Evans

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This has been bouncing around my head for a while, so here it is. Maybe the resident steel experts can help me out. I know other people have to be wondering it too.

What are the practical differences between O-1, 1095, 1084, and A-2? I can tell the difference grinding A2 and O1, but past that, what's the difference? Don't say air vs oil hardening, we know that. I mean in knife applications, edge retention, toughness, etc. Why were a bunch of pocket knives made in 1095?

And, if you happen to have a different steel you want to explain, by all means, throw that in there too.
 
Well, the 1095 thing is easily explained. It got a lot of internet hype because some of the most popular larger knives were made in it and buyers just see the steel designation as part of the hype without really understanding why that steel is good at a particular role. The knife companies made use of the popularity of 1095 and the fact that they can easily use protective coatings to minimize corrosion to sell a lot of folders. There are plenty of people who will buy the same knife in every version offered, so just because you have model xyz in cpm154, D2 and 440C doesn't mean you can't go for a whole new round of sales in 1095. Maybe even add S30V to really get every dollar out of the design.
 
O-1 = tougher than 1084- good for hard use larger knives and choppers. A good steel with fairly simple HT.
1095 = hard edge and can get a hamon - good for slicers with gentle use, kitchen and Japanese blades. HT is straight forward, but requires better temp control and the proper oil or a water quench.
1084 = gets hard with a simple HT - a great all around steel. The simples HT with a blade nearly equal to 1095.
A-2 = tough and has good edge retention - good for large blades, and sharp cutters with moderately hard use. Air hardening is an advantage in controlling warp. Requires more advanced HT equipment.
 
Thanks guys! That's what I like to see. So for small EDC 3/32" stock fixed blades and pocket knives, A2 or O1?

I only have a 2x42 grinder with no way to slow it down for post HT grinding, so I've been grinding al my thin stock knives from A2 just for the warp control. It's nice to know they'll take a nice edge as well.
 
Slowing down your grinder after HT is recommended but not required. You just need to use light pressure and you can't hold the blade on the grinder for too long. You'll screw up a couple of blades learning this but you'll get the hang of it. Don't wear gloves when you grind so you can get a better feel for the heat of the blade.

- Chris
 
That grinder runs FAST. If I can find a smaller drive wheel I might try it, but as it is, I'm just too afraid to try. Maybe I can buy some 1084 to practice on. A2 is kind of expensive practice steel. Lol
 
medicevans said:
Thanks guys! That's what I like to see. So for small EDC 3/32" stock fixed blades and pocket knives, A2 or O1?
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It really depends what you're going for; they're both good alloys. Assuming they both get appropriate HT, A2 should keep an edge longer and resist corrosion better. O1 will likely be easier to touch up.

When it comes to low-alloy steels, I'm an O1 guy myself, although 1084 is also pretty darn good. If I want a higher alloyed steel I skip A2 and D2 and go right to CPM-3V, CPM-154 and so forth.
 
Here are my thoughts about the above steels, but I have only worked with O-1 but studied them all.

O-1 and A-2 I would expect to be higher quality in the manufacturing and of course are much more expensive usually. Be particularly careful where you buy 1084 and 1095.

A-2 then O-1 then 1095 then 1084 will be the order of wear resistance if done at the same Hardness with proper heat treat.

A-2 will have larger carbides. The others should be relatively small. For instance, you may be able to make a finer edge on O-1 then A-2.

They will all be good at toughness. I think the Hardness level will be more important than the steel you choose as far as toughness goes.

1095 will take a hamon. (1095 seems to have the most failures during heat treat because of its requirements for a fast quench).

I reserve the right to be wrong about any of the above information.

David
 
I think its a little unreasonable to take out the differences in processing (air vs. oil quench, etc.). That's where as many differences lie as there are in end performance. People wanted a little more edge holding that 1084 was giving them, so went to 1095. They got tired of the cracked blades or didn't have fast enough quenchant to take advantage of 1095, so went to O1. Then they discoved that thinner cuts better, and started grinding O1 thinner before heat treatment. Now they have warped blades and maybe some cracks. Now it's on to A2. A2 is too expensive and the heat treatment is too complicated. Now we're back to 1084. It's a vicious cycle.
 
I have no problem paying for A2, if it means I can not ruin steel trying to grind after HT. I don't do my own HT, so how complicated it is has no bearing on my choice.
 
Then you need CPM M4. Very heat resistant. I thought you meant general differences, not your particular differences.
 
Me2, I was asking about generalities. I misunderstood your post. Sorry bout that. Thanks for the information.

I am asking about generalities in order to have the information to be able to decide what steels to get for my particular uses. I want to know why I'm using something instead of being told "use steel x, it's awesome."

I think I'll stick with A2 for my 3/32" stock blades as leaving .030" edges before HT is pretty thick and I'd like to go thinner before HT. Is thinner edge pre-ht feasible with A2?
 
In theory, you could go thinner with A2 before heat treatment, with respect to warpage and such. In practice, A2 requires higher austenizing temperatures, 1700+ for A2 vs. 1400-1500 for the others listed. If the A2 is protected, it might be ok. If not, you'll need to leave on extra material or use a lower hardening temp steel. I ground a couple of O1 blades down very thin, like 0.020" before heat treat, but they twisted in the quench. In hindsight, that was mostly due to my cobbled together heat treatment set up than any fault of the steel. If you're using a good heat treater, they have very nice equipment that can return your blades without any surface issues, in some cases not even coloring from tempering. Be sure to ask, as not every one has or uses this equipment for knives. I talked to a company in NJ that basically said I could do all but sharpen the blades, as they used vacuum ovens and such. Sadly, they went out of business. I've used O1, 1095, and have some A2 on the bench now. Of the two I have final results for, O1 wins hands down, except for price.
 
Choose your steel based on the properties you want in your blade, not based on whether or not you can HT it in a coffee can.

Brad Stallsmith at Peters' HT for the win. Thick or thin, air-hardening or oil-quenched, he returns my blades straight, clean, at the Rc hardness I request and ready for final polish every single time.
 
I have used O1 since I started as it was the easiest to come by. it was a little expensive but not too bad. I have had very little warping on any of my blades that I couldn't fix and most of them have been in 1/8" with a couple in 3/16". I just recently picked up some 1084, 15n20 and 52100 (thanks Aldo) and although I plan on trying some damascus with the 1084 and 15n20, I also plan on making blades with all three of the steels. As an average for all, I would say use O1 for an EDC.
 
james terrio said:
Choose your steel based on the properties you want in your blade, not based on whether or not you can HT it in a coffee can.
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Unless a coffee can forge is all you have or want. The steel you choose should always match your process and equipment.
 
Hesparus said:
Slowing down your grinder after HT is recommended but not required. You just need to use light pressure and you can't hold the blade on the grinder for too long. You'll screw up a couple of blades learning this but you'll get the hang of it. Don't wear gloves when you grind so you can get a better feel for the heat of the blade.

- Chris
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What Chris said.

I have a 2x42 Craftsman and pre-HT, I grind with gloves to get it where I want it quickly. I started leaving more meat on my blades pre-HT and doing more final grinding post-HT.

I take the gloves off post-HT. Your fingers/thumb will tell you when you've ground too much. Keep water handy and dunk often. Use sharp belts, dull belts build up heat quicker. Depending on thickness, I can usually get two passes before dunking the blade.
 
I'm barely an amateur, but have been going through this myself.
I've settled on Aldo's 1084 and A2 as my go-to steels, and here's why:

A2 out-performs O1 in terms of edge retention (wear resistance), corrosion resistance, and dimensional stability.
1084 is cheaper and more reliable to heat-treat than 1095, AND Aldo's variation is tops.

Once I came to understand that to get the best out of O1 I needed to use the kiln, I realized that the O1 heat treat was MUCH more complicated than A2, which also needs the kiln. Either I'm struggling to get the knife outof the foil packet and into the oil when it's super hot, or we have to burn up shielding gas in exchange for making the pull-quench operation smooth and safe. Might as well just throw the A2 knife, packet and all, on the aluminum plates and be done.

So A2 costs a bit more, but it performs better where it counts to me. Honestly, though, the heat-treat simplicity alone is worth the extra expense. Now if you're sending your blades out, this matters less. BUT if you decided you want to heat-treat at home, start with 1084.

Hope that helps.

-Daizee
 
james terrio said:
Choose your steel based on the properties you want in your blade, not based on whether or not you can HT it in a coffee can.

Brad Stallsmith at Peters' HT for the win. Thick or thin, air-hardening or oil-quenched, he returns my blades straight, clean, at the Rc hardness I request and ready for final polish every single time.
Click to expand...

What are you leaving for edge width on O1 and A2 prior to heat treat?
 
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