Making a knife out of an old file?

[svk9612]

Thank you sir. I wouldn't have taken your advice as criticism, and I do appreciate it. I guess I left out the part about annealing the files, which
I do. These knives don't normally sharpen so easy as to indicate softness; I will though raise the tempering heat. Would 450 be a better choice? I do normally try to get a more orange color when I
heat for the quench, I just didn't go into enough detail. I've always gone by color, never used a magnet. I need to get back into it, I've been kind of lazy the last couple of months. Thank you for your advice.
Be safe,
Steve

 

[LRB]

Sounds to me like your on the right track for the method you are using. I did mine much the same for a number of years, even the 425o temper, but I got just enough feed back on them being a little hard to sharpen, that I upped them to 450o. If you get no complaints, you might want to stay with what your doing and experiment with one at 450o, and then decide if you want to change. One problem I ran into, was that many customers do not know how to sharpen, and do not have stones that will get the job done easily.

 

[dlemaster]

Wick
That's great information . I didn't know about using several temper heats. I'm going to try that.
Thanks.

Regards, Dave

 

[LRB]

If you are using your kitchen oven, do your best to use an oven thermometer that you fully trust. Oven thermostats are notoriously off. In the 400o range, mine is almost 75o hotter than the setting.

 

[davy]

If you are using your kitchen oven, do your best to use an oven thermometer that you fully trust. Oven thermostats are notoriously off. In the 400o range, mine is almost 75o hotter than the setting.

Howdy Wick

A couple of questions here ...

1) When tempering in the oven .. do you just turn the oven off and let the blade cool down in the oven between heats ... letting the oven cooling period retard the cooling speed somewhat .. or do you just pull the knife from the oven and set it out to cool more quickly in the air?

2) When do you normalize your steel .. between what steps a.. and may I ask what your process is for doing so?

If possible ...it would be nice to hear some of you guys normalizing, quenching, and tempering process from start to finish. :hatsoff:

Thanx

Davy

 

[LRB]

Bring the oven up to heat first. You may have to play with it a bit to get the temp right. Once you have your desired temp, put the blade in edge up when possible. I always used the middle rack, some may have other ideas. Your oven will be hotter up higher, but if you leave the thermometer close to your blade, that will give you the temp, which ever rack it's on. After each hour remove the blade and leave the oven on. The blade should cool in about 15 minutes. After the last heat you can turn the oven off and leave the blade in, or take it out. No matter at this point. Any heat source that will bring the blade somewhere above non magnetic, or close to a quench heat will begin the normalizing, which is just a quick anneal. Three times like the temper, letting it cool between heats. After the second heat, it is a good time to correct any warpage. I found that if you continue normalizing until you stop getting warpage, you will have less, often none after you do the hardening quench. Heat the blade if possible, in a point down position hanging from a wire, or clamped in position, or just hold it with tongs. You can reheat as soon as all color has left the blade. I have a very large propane torch that I used to use. You can also forego the normalizing, and just thouroghly anneal the blade by heating it to a red orange, hold the heat for a maybe a minute, do not let it over heat though, if you ever have a piece of steel go yellow, throw it out and start over, the grain has grown beyond the point of recovery, then plunge it into a bucket full of vermiculite and cover it well. The next day it will be pretty much annealled. To get a maximum anneal, you would have to hold that heat for around ten minutes, and have decarb protection, making it all a bit difficult. I have a heat treat oven making the process much easier.
Here's a little tip to correct warpage. After the hardening quench, and the blade is still uncomfortable to handle without gloves or a rag, you have about 5 minutes in which you can straighten it with your hands. Things are still moving inside the steel for a short time. If you have warpage after the temper process, you can put the blade in a vise, it needs to be polished where you can see the colors, with a small propane torch, apply heat to the spine where the warp is until the area turns straw color, over correct a little bit, and pour water on it to cool while you continue to hold it. DO NOT let the heat go to the edge though. You may have to repeat this, but it does work. I learned this years ago from a Bill Moran tape. Good luck, take care

 

[davy]

Thanx for the explanation Wick! :grin: Appreciate amigo! :thumbsup:

Davy

 

[J.D.]

I's my understanding that triple tempering works only with steels that contain chrome. It is also my understanding that one should wait 24 hours between each tempering cycle to allow the grain structure to change, as much as it will, from each tempering cycle.

I haven't traveled in knife making circles for about 10 years, so I'm curious as to where you came by your triple tempering process for file steel?

Thanks,
J.D.

 

[LRB]

Hi JD. A triple temper is widely used for any steel, with a few exceptions. In a case where it does little good, it does no harm. With some steels, including 01, which does contain chrome, time in temper depends more on thickness, although with knife blades, this is not a real issue. Some makers will temper for one set time and be done with it. I am more comfortable with a triple temper as I strive to produce the best blade I can. The only mention I have ever seen on waiting 24 hrs between, came from Ed Fowler concerning 52100 ball bearing steel, and Mr. Fowler is not a metalurgist, but then neither am I. In my research, metalurgists disagree with Mr. Fowler on this, but new discoveries happen every day in this world, and I am sure that metalurgists disagree on some things among themselves. From everything I have read on the subject, once the steel is down to room temp, nothing more is going to happen. The last article I read concerning the triple temper was from a metalurgist/knifemaker who does much experimentation, and has all the equipment, or access to, to test his efforts. He recommended the triple process and in his opinion, it was required with most steels in order to allow a more complete, and stronger result. As you probably know, tempering allows some of the martinsite to revert back to layered pearlite, at the sacrifice of some of the carbon atoms changing position in, or leaving the atomic cube, making the steel softer, yet stronger. It is my understanding that with three heats, all that is going occur, will. I do not recall just what the cool downs accomplish, but he had reasons for it. Possibly to slow the process, allowing a better transformation. As I said, I am not a metalurgist, but I study all that I can understand about it, when I have time. If you wish for a better explaination, I will see what I can find. Take care my friend.

 

[LRB]

A bit more on the above. After re reading my post, I don't think I was clear on the steel changing after assuming room temp. It can and will after the hardening quench because of stresses. The tempering takes care of this. Once you have achieved a maximum temper, any changes later on are so minor as to be insignificant. After checking some notes, I can add the following. A 100% change from austenite to martinsite is not possible, and retained austenite can transform to martinsite after an incomplete temper, making the steel harder, and more brittle after time. Incomplete being the key word. Therefore, it is wise to do as complete a temper job as is practical, in order to transform as much of the retained austenite crystals to pearlite. Two, to three heats is considered sufficient to acomplish this goal in most of the commonly used knife steels. The length of the heat times are dependent on the steel, and thickness, but it would seem that there is no too long a time in temper. This applies to the simple steels as well as some of the more exotic. We all know that the resulting hardness from tempering is dependent on the level of heat, but the transformation of retained austenite to pearlite is also a matter concerning time to do so. It would seem that only so many carbon atoms will leave or shift in the atomic cubes at a given heat level, This I am not clear on, but it seems to be the way it is. In other words, as I understand it, which could be a screwed up grasp of things, in theory, one could leave a blade all day at a given temp, and find it no softer than after a few hours at the same heat, but any retained austenite would be coverted as much as it ever would. Raise the heat and then more of the martinsite would convert to pearlite, making the steel softer. Many novice, or uninformed knifemakers assume the degree of hardness is the only important part of heat treating, but in reality one should be concerned as well with toughness, and be seeking a balanced combination, depending on the intended purpose of a particular blade.

 

[Charles/NM]

Let me interject my two cents worth here:
IMHO, y'all are making this knife making thing way too hard. I've made well over 700 knives. I started out using saw blade material but it was too hard to find in the quantities I needed so I changed to O-1 tool steel. I made a few file knives for customers who insisted on them but don't make them as a part of my trade. I'll do it with the caution that the knife may be not be as satisfactory as one made from O-1. I am thinking of making one for myself just for fun because they look cool if you leave some file marks on the unground sides and top and are historically correct for the early times we are interested in.
Over the years I've decided that a few knife makers have tried to mystify the knife making process like the famous Fowler triple tempered ball bearing knife. Keep in mind he forges his blades. Stock removal blades and forged blades are NOT the same! Not even from the exact same steel. I make both, but mostly stock removal. Also keep in mind I'm a retired mechanical engineer and a firm believer in the KISS principle.
I use mostly Starrett brand tool steel. It ain't cheap. And just like a turkey it comes with cooking (hardening) instructions on the wrapper. The tempering temps cited here are way higher than they recommend and what I use. As a side note I can assure that a magnet is a good indicator of the correct 1450 to 1500 degree quenching temp. I go a little higher than the magnet indicates just like Moran tells you to do in his tapes and articles. I get a red-orange color, closer to orange, with the magnet in the subdued light of my shop. You can tell when you've gone too hot because you'll find you're making a sparkler as the carbon burns out of the steel. The reason for using a magnet is that the level of ambient light makes a big difference in how you see the color of heated steel and the magnet gives you a consistent base line temp reference.
I use olive oil for my quenching medium. It's characteristics are very close to commercial quenching oil.
From there I go to a pre-heated toaster over at 357 degrees. That's a little lower than Starrett recommends but in my shop and with my process it makes for a perfect balance of hardness and toughtness in the blade. I have never had a stock removal blade break or be too soft.
Forged blades are a completely different subject and in my shop require a different approach.

 

[LRB]

Other than having to remove stresses, how would you treat a forged 01 blade any different?

 

[Charles/NM]

I heat treat the forged knife in my coal fired forge, not with the oxy-acetylene torch I use for stock removal knives. If my stock removal blade is longer than 7" or of an unusually heavy section I heat treat it in the forge too. I make a slightly rich, slightly oxygen starved pocket in the firebox. The blade is pulled back and forth in this fire with the cutting edge down. The blade is turned on it's side ever so often to keep to keep some color in the back of the blade too. I have perviously checked the color of my steel for it's nonmagnetic state so I don't overheat the blade in the fire. I find it's very easy to over heat in the forge. Once I have the blade to heat and have held it there for at least 30 seconds I plunge it point first into room temp olive oil. When it's cool enough to touch I put it in a preheated toaster oven for an hour at 375 just like my stock removal blades.
Now that I wrote this down I can see that it's not all that different an approach. I guess it's mostly my mindset that's different when I forge. I do find my forged blades to be a lot harder and more corrosion resistant than my stock removal ones. I can only guess that carbon is infused into the steel from the forge fire and some work hardening has taken place.
I don't make a lot of forged blades partly because O-1 isn't the best choice for a forging steel, it's prone to cracking if hammered too cold, but it's mostly what I have on hand. I am going to try to straighten out an automotive coil spring and see what results I get with that steel.