1084 Performance ?

[B.V.]

Quick question for you guys that know all this stuff....I have been shooting for an edge hardness of around 62 HRc with O1 differentially heat treated in a "home built" forge. I have had pretty good luck (I think) so far. However, after reading some of the recent threads I am thinking about giving 1084 a try. Can I get that out of 1084 as well? I may even try to etch it afterwards.

 

[Ed Caffrey]

Unless this blade needs to be that hard for a specific reason, I have to ask....Why would you want an Rc 62?
In my opinion that's far too hard. Most "high performance" forged blades don't exceed 57-59 Rc.
Almost any forgable steel would suffer from a level of hardness that high. The edge would need to be very thick to hold up with an Rc 62, which would make the cutting resistance very high, and it would be a real pain for a customer to resharpen.

My thought is to concentrate on geometry and how effiecient the edge cuts rather than thinking that a high hardness level will help (I'm assuming that your line of thinking is that the harder the blade, the better it will be.)

 

[B.V.]

Thanks for the reply Mr. Caffrey. You are right in my thought process. I read some where that some of the hard use tactical knives are made that way and I wanted to duplicate it on my own for use at work (Since I can't afford to buy them). After having made a couple of them I see why they are not cheap! I am using the stock removal method (for now) and wanted a knife that would take a beatin. The torture tests have gone well but I thought maybe 1084 would be even better and easyier to work with after some of the reading I've done. The edge stays sharp a long time....but it is hard to resharpen for sure. Right now I'm at my limit attempting to grind straight lines. Geometry is way above me still but I will try to learn more on the subject. Oh yeah....I think customers are years down the road anyway. I would post photos if I knew how to bring them over from photobucket!

 

[Ed Caffrey]

Thanks for not taking my input the wrong way. After reading your post, it seemed that you were equating hardness with the quality of the blade. With the the methods your using, I think that 1084 or 1080, oil hardened, and tempered at around 415F will give you the combination of toughness and cutting ability your seeking. Much will depend on the geometry, but with that steel and the tempering temp I gave you, a very fine convex edge works very well. To add some toughness, you'll want to increase that tempering temp to about 430-450F. If your more concerned about having a harder edge, then you can decrease the tempering temp to 400F. At that tempering temp the edge will not be as durable, but will be harder....if thats what your seeking.

Good Luck!

 

[B.V.]

It is...Thank you for taking the time. I think I will try some then. Just for info., I will be trying to make a hunting knife for elk soon. The info will be especially helpful on that project. Thanks again.

Brad

 

[LRB]

My question would be, how would you know, it was that hard? Do you have a rockwell tester, or other means of knowing? Yes, you can get that hardness, but I have to completely agree with Mr. Caffrey. Why? iF you reach the point of selling a good amount of knives, many of your customers are going to complain about them being too hard to sharpen, and they are going to be brittle in the edge. A long lasting edge depends more on the steel, and it's proper HT, than it's acual hardness. Hard, does not always mean that you will get good edge holding, just because. Early Randall knives were in the low 50's, up to around 54 Rc in hardness, and they built their reputation on such knives. If you have a way of gaugeing it, 1084, at around 56, to 58, will give you fine performance, assuming everything else is good. If hard mean't everything, then all custom knives would be around 64/65 Rc. Properly HT'd, 01 will surpass 1084, at almost any hardness over 55 Rc, even if the 1084 IS 62 Rc., simply because of the alloys, and extra carbides. 01, is formulated for abrasion resistance. Now then, with a simple forge arrangement, you will not get the best from 01, but you can get the best that 1084 has to offer, as long as you don't try to make a better mouse trap. Each formulation of steel, has it's limits, and you need to work with those. Shoot for around 56/58 Rc, with 1084, and you will have a very good blade.

 

[B.V.]

I wish I did have a way to test it, but first I would like to get a good grinder. I'd also like to know how hard the rest of the knife is. My "guesstimation" is from following a recipe from a video and from reading online. With all three of the knives I've made so far, each has gotten better and all three perform better as far as edge retention goes than the store boughts I have used. And yes...the O1 does seem to cut very well. In the mean time, I'm not even sure I can spell geometry.....

 

[Stacy E. Apelt - Bladesmith]

Ed's advice is right on. Unless you are using a high alloy stainless steel, forget Rc62. Shoot for a quality HT and a final Rc57-58.
Stacy

 

[B.V.]

Will give that a whirl....Thanks!

 

[ryan9977]

the only blade i would want that hard would be a kitchen knife.....i commonly use kitchen knives in the 60+ range.....ryan

 

[jdm61]

Ed is right on the money. I was originally using Admiral 1075/80. I was quenchingit in Tough Quench or worse, home brew and tempering it at 400 in the kitchen oven. I got some of Aldo's larger 1084, which has a higher carbon content and some Parks #50. 400 in the Paragon left it a bit on the "chippy" side. By contrast, I temper W2 at 450-475 and it is still probaly 60 or harder and holds up just fine. But in the case of the W2, a bunch of guys had already figured out the correct recipe for Don Hanson's stuff, so that made life easier. You are going to have to play around with anything new a bit.

 

[Kevin R. Cashen]

For what it is worth, and you can take this or leave it, as it is my opinion, I believe that 57HRC is too low for anything but the larger choppers. Of course each steel will determine which Rockwell you can indeed go to and be safe with. 62hrc may be out of line for larger blades or anything that will see a lot of impact but for a skinner or other blades that will do a lot of slicing and needs to handle wear it is not at all out of line. The problem comes in when you have to account for abuse. Most of us guys that forge tend to err on the softer side because of all the hype and the fools who are influenced by it and will abuse their blades. Roman Landes has a nice section in his book that covers how much more performance we could all get from our knives if we would just use them correctly. A pure slicing knife at 62HRC or even a little higher would be a great edge holder and performer as long as we didn't try to use it for a hatchet. So instead we tend to make more general purpose knives to account for this kind of abuse instead of getting the high performance of specialization. The flip side of all this is how one could make a great little slicer out of something like wootz that is only 45HRC and gets all of its slicing ability from the carbides, but if the same idiots used that skinner for a hatchet it wouldn't chip out, it would wrinkle or roll.

Abrasion resistance is the one thing that we can really play with everything thing else in our heat treatment is a balancing act between strength and toughness. Excluding alloying and working simply off from carbon content (which is entirely applicable to a 1084 discussion) the most effective way to balance strength versus toughness is with Rockwell type hardness. Since 1084 is eutectoid we eliminate proeutectiod carbides so now we are very, very relevent with this discussion.

Without the benefit of extra carbide, edge holding will be via material strength alone, so the greater the hardness the greater the edge holding but this will be at the expense of toughness. But if you go for toughness the strength will drop and the edge will not be as durable. So if you are looking to cut and not chop higher hardness will allow the edge to go thinner with the higher strength. A fined grained 1084 will handle a 62HRC with a thinner edge much better than 1095 and may indeed need a higher hardness to get the equivalent cutting ability in a thin edge. 1095 could go much lower in overall hardness as long as the carbides were present to make up for it in abrasion resistance.

The whole flexing issue that I so often reiterate ad nauseum has most folks very confused about how knives will stand up or fail due to hardness. Flex is a function of cross section and geometry, strength is a function of overall hardness via heat treatment with alloying, and toughness is a function of overall hardness via heat treatment with alloying playing a huge role. Abrasion resistance is a function of alloying that is heavily influenced by heat treatment but can be very conveniently independent of strength or toughness. So we can have a very strong blade with abrasion resistance as well as a very tough blade with abrasion resistance. One will handle impact very differently than the other by either deforming or fracturing. A thinner edge will flex much farther and return to true but yield via plastic deformation (wrinkling) will always occur sooner than fracturing. If you want to avoid either you can up the amount of force required to deflect things at all by making the edge thicker thus increasing the amount of material that has to move. Thus it is the softer edge that sees the most benefit from being thicker due to the nature for brittle failure.

1084 gets no extra help from alloying or chemistry, so it is more important with this steel to decide if this will be an excellent slicer, a good chopper or a mediocre compromise. The excellent slicer could be HRC 62, the good chopper could be 57-58 HRC, mediocrity in either category would be a compromise somewhere in the middle. Mediocrity may be boring but it is also much safer.

 

[Sam Salvati]

Could "happy medium" be substituted for "mediocrity" if the idea is to have a knife that does both equally well, not the best they COULD do it as if the knife was specialised to do one or the other, but still good?

 

[Stacy E. Apelt - Bladesmith]

My advice was to a novice who has no ability to control and verify his HT. The recommended range should allow a serviceable blade ( who's function is unknown).

Most of my blades are higher Rc, with the exception of camp knives, bowies, and chopping use knives. Slicers ,indeed, can be a very high Rc and excel at their task. Problems occur when a knife is a general use knife that gets a blend of cutting tasks.
I feel that steel selection, edge geometry, and quality of HT are more important than a difference of 2-3 Rc points. Point being that a skinner with the wrong edge won't cut worth beans at Rc65, but a thin,hollow ground K-mart cheapie can slice up a deer at Rc56.

Kevin's blades are made under strict control and he can certify that they are at an exact set of parameters.
A knife made by an inexperienced maker,from O-1, with the HT done in a "home built" forge, with the knowledge from a video and some articles.....would be best left a bit on the softer side to avoid many of the problems that could occur.

I agree totally with Kevin on the use of 1084 to learn on. It will eliminate many of the problems that can arise with more or less carbon or with alloys added. I wish more people would understand the eutectoid. A plug for Aldo's new 1084FG is due here. This should make some excellent blades. It is eutectoid steel (.82C) plus a touch of molybdenum and a trace of vanadium to reduce the grain size.
Stacy

 

[mete]

It's still mediocre as it does neither job well. Same as 'all purpose flour'. Doesn't make the best bread and doesn't make the best cake . It's then all purpose HT rather than specialized .

 

[Sam Salvati]

It's still mediocre as it does neither job well. Same as 'all purpose flour'. Doesn't make the best bread and doesn't make the best cake . It's then all purpose HT rather than specialized .

OK, got it thanks Robert.

 

[Kevin R. Cashen]

Sam, "happy medium" would simply be a euphemism, and if it is one thing can’t bring myself to do in any area is resort to euphemisms. I don’t like candy coating reality in order to allow more comfort in not dealing with it; that is the slippery slope of political correctness. It is a horrible thing to sacrifice accuracy for the sake diplomacy, in matters of taste and opinion one can be diplomatic e.g. “that dress makes your @$$ look HUGE!” vs. “I liked the other dress more than that one”. But if one replaces the sights on a rifle with loops for fishing line in order to make the ultimate backwoods survival fishing pole they sacrificed a good rifle to make a mediocre fishing pole not matter how pretty we phrase it.

However if accuracy leaves the semantics too cold and harsh for folks another term that could be used is “compromise”, the general purpose knife is an acceptable compromise of strength versus toughness. After all, due to toughness so often being the inverse of strength almost everything we do in heat treating is matter of finding an acceptable compromise of these two extremes. A 30HRC piece of 1084 will have all the toughness we could ever want, but would to offer no strength. A 66HRC piece of 1084 would have the most strength we could get but it would lack any toughness. Our job is to find the compromise that works best somewhere between these two extremes. But since we deal with edges that need to defeat other materials, our working range naturally falls more on the strength side. Our goal is to find a minimum strength that is just a bit more than the strongest material the blade could encounter, the real hard part is predicting what that material could be depending on the rationale of the end user, however the life of the edge could depend on how much more strength we give it beyond that minimum.

Edited to add- The original question concerned O1 and 1084 at HRC62, I personally have found much success with both of these steels at this hardness level for many applications in a thinner edge. Many variables will affect this but they can be overcome. I guess things change from shop to shop I thought I would just share how this has worked in mine.

 

[Kevin R. Cashen]

...A knife made by an inexperienced maker,from O-1, with the HT done in a "home built" forge, with the knowledge from a video and some articles.....would be best left a bit on the softer side to avoid many of the problems that could occur...

And indeed grain size, quaility of austenization and proper rate of quench will all be critical to determining what final hardness a thin edge can handle in use. Previous thermal threatments and steel conditions will also heavily affect things, all the time I am seeing things that really can only be dealt with in proper normalizing and other treatments prior to final heat treatment.

 

[Sam Salvati]

Sam, "happy medium" would simply be a euphemism, and if it is one thing can’t bring myself to do in any area is resort to euphemisms. I don’t like candy coating reality in order to allow more comfort in not dealing with it; that is the slippery slope of political correctness. It is a horrible thing to sacrifice accuracy for the sake diplomacy, in matters of taste and opinion one can be diplomatic e.g. “that dress makes your @$$ look HUGE!” vs. “I liked the other dress more than that one”. But if one replaces the sights on a rifle with loops for fishing line in order to make the ultimate backwoods survival fishing pole they sacrificed a good rifle to make a mediocre fishing pole not matter how pretty we phrase it.

However if accuracy leaves the semantics too cold and harsh for folks another term that could be used is “compromise”, the general purpose knife is an acceptable compromise of strength versus toughness. After all, due to toughness so often being the inverse of strength almost everything we do in heat treating is matter of finding an acceptable compromise of these two extremes. A 30HRC piece of 1084 will have all the toughness we could ever want, but would to offer no strength. A 66HRC piece of 1084 would have the most strength we could get but it would lack any toughness. Our job is to find the compromise that works best somewhere between these two extremes. But since we deal with edges that need to defeat other materials, our working range naturally falls more on the strength side. Our goal is to find a minimum strength that is just a bit more than the strongest material the blade could encounter, the real hard part is predicting what that material could be depending on the rationale of the end user, however the life of the edge could depend on how much more strength we give it beyond that minimum.

Edited to add- The original question concerned O1 and 1084 at HRC62, I personally have found much success with both of these steels at this hardness level for many applications in a thinner edge. Many variables will affect this but they can be overcome. I guess things change from shop to shop I thought I would just share how this has worked in mine.

OK got it, it seemed harsh at first but now you explain it I understand much better and no longer feel the same sentiment. How would you address a customer that would want something that would not be a "DO ALL AMAZING DEAL ULTIMATE SUPER SURVIVAL KNIFE" but is looking for a not completely specialised knife?

 

[the possum]

How would you address a customer that would want something that would not be a "DO ALL AMAZING DEAL ULTIMATE SUPER SURVIVAL KNIFE" but is looking for a not completely specialised knife?

Use CPM 3-V, at fairly high hardness. Then you'll have strength, wear resistance, and toughness all at the same time.