Knife heat treatment

[crockett]

I know 440C isn't PC but I use it because it is easy to work. In any event, I am confused about double drawn tempers and also sub-zero quenches. Are these treatments suitable for 440C or were they intended for other type steels?
This is for a PC folding knife I copied from the Smith's Key of 1816. I'll be using this one rather than hanging it on the wall so I want the best treatment.

 

[LRB]

Don't know about the double drawn tempering, but the blade will need a full cryo treatment, which is more than just sub-zero, for the best results. I worked in it for about ten years. Late seventies to mid eighties. I sent my blades to Paul Bos in CA. for heat treat. You might check with Texas Knifemakers Supply for HT services. Without the needed equipment, you will not get the best HT for that steel if you do it at home. You need a programmable HT oven. Protection for de-carb and scale. Liquid nitrogen. And thick aluminum blocks for the initial plate quench, although some makers, a few, not many, oil quench it, I would expect a lot of flame up with that method. With a good HT, with cryo treatment, 440-C makes a good blade that holds an edge quite well. Skeptics are welcome to believe that or not.

 

[Bo T]

I have a Buck 110 from the 70's that purportedly has a 440C blade. It is great for holding and taking an edge. I don't know that cryogenic treatment will increase its performance by much though.

 

[LRB]

440-c is prone to excessive or at the least, undesired amounts of retained austenite. The LN cryo treatment included in the quench process does well in promoting the conversion of more RA to untempered martensite, and requires it to be tempered afterwards, whether or not it was already tempered. I suppose that may be the "double drawn tempering", which threw me off a bit by that wording. All steel benefits, at least some, from a double, or even triple temper. In testing, there is a noticeable difference in edge retention if cryo is included in the heat treat process for most HC stainless steels. Does little to nothing for the common carbon steel blades, including 01. By the way, Paul Bos did the heat treating for Buck Knives, and also took on outside heat treating for makers like me, in another part of the building. Cryo was SOP for the Buck Knives, 440-C, ATS-34, and 154-CM. I don't know about D-2, I never worked with it.

 

[crockett]

I did one D-2 and it took a good edge. I showed it to Steve (?) at Knives A Lot(years ago) and he really liked the knife. 5" deep belly clip point, full but tapered tang, stag scales, no guard. Rawhide sheath. 3/16" so a big "hunk of knife".
I was told you couldn't get a mirror polish on D-2 , there was an "orange peel" effect however I got what I consider a very good polish.
On the Buck 110- now a days I think they are using a different steel than 440-C but I'm not certain.
On the 440-C I was told the second draw would raise the hardness one point which doesn't seem to be a big deal. The sub-zero quench I always have that done as I also was told of the benefits. I use Texas Knifemaker's Supply. BTW for those who made not know- they only treat air quenchable steels.
Well.....I guess I'll just keep on keeping on- I wasn't sure if I was missing something from the second draw. I don't think it would be that beneficial in my situation so thanks for the help.
BTW this folder- it's a square tang with no kick, regular slip joint. I am using a bronze bushing on the blade rivet and the anchor (spring) rivet is short and covered by the scales- something you see on a few pre-1840 folders. My biggest problem to date is the nail nick. The modern method is a milling machine that cuts the nick flat across the top and then circular on the bottom but if you look at the original blades the top and bottom are often curved and you'll see one side deeper than the other- which indicates to me the nick was stamped while forging rather than ground out. Right now I'm using a Dremel tool and being real careful but I'm not happy with the method.
I suppose if I continue in this direction I'll get a better name stamp with an insignia and also a nail nick stamp and try forging my own blades. I think such would require 01 or something similar. If the steel was air quenchable and I heated it so I could stamp the nick- the steel would harden unless I then annealed it. I think.

 

[LRB]

Most of the so called stainless steels are prone to have more retained austenite after quenching than do common carbon steels, which usually retain only a tiny amount of austenite. A single temper with the stainless, depending on heat and time, can convert some more of the RA to martensite. Especially if water quenched from that temper. The newly added martensite adds a degree of hardness with some brittleness, and it too needs to be tempered, so a second temper is advised. If the stainless is cryo treated after tempering, once again more martensite has been produced from the RA, and it needs yet another temper. What is commonly known as a sub-zero quench, is usually not much colder than -100°. A cryo treated blade is brought down to around -300°, or a bit lower, using liquid nitrogen for a timed soak period. The results are much improved over a common sub-zero treatment.

 

[LRB]

For the nail nick. Have you tried a graver type chisel? Before HT of course.

 

[crockett]

Thanks on the tempering. On the graver- I've thought about that but I've been a little fearful of a stray hit on a finished blade. Maybe what I should do is start the groove so it is "in place" and then grind the blade a bit and then deepen the groove and then grind the nick some more, etc.
The funny thing about this "recreating" thing is on the original they likely just knocked out the blades very quickly- a tilt hammer, a stamp for the nick, another stamp on the logo- and they're done. I'm spending far more time on stock removal, etc.

 

[LRB]

Yeah, that seems to be the way of these things. A so called "penny knife", as simple as they may be, can take enough time and trouble to become a bit more pricey than a penny.

 

[Bo T]

Google Albert Craven. He purportedly was able to forge a gross of blades in a day. The heat treatment was quench in water and temper to blue.

 

[LRB]

Thanks. A very interesting and entertaining video, and a very accomplished craftsman.

 

[Bo T]

Thinking about it, and limbering up my electronic abacus, Albert could have forged over a million blades in his life. :shocked2: