Heat Treating Rebar Knife

[Mrhappybottms]

Ok, first off, i know that Rebar is not a good metal for making knifes, but i just started trying to make knives and i didn't want to waste the only piece of high carbon i have, but the knife is coming out better than i thought. Is there a way of heat treating the knife to make it stronger then heat treating it the normally? or should i just treat it as i would with high carbon. (and by heat treat i mean the whole prosses, including the temper)

[Rich Hale]

Try the process you use and see how it turns out,,one of the reasons i always chose high grade walnut for gunstocks is if it happened to come out really nice it wouild be a lot better than if i use pine!

[Woody]

I would take a piece of the rebar and heat it to non magnetic, and quench in oil. Then hit it with a file, if the file skates over the metal without cutting it, you have some pretty high carbon steel and you can heat treat your knife accordingly. If the file will cut it, reheat the steel and quench in water, then try the file test. If that hardens the metal to your liking, heat treat your knife using a water quench. My guess would be that there isn't enough carbon in the rebar to be suitably hardened for knifemaking purposes. A while back I saw some ASTM minimum requirements for carbon content etc for various grades of rebar but as I recall they were minimum requirements and the maximum amount of carbon in rebar can vary considerably. I had some old stuff laying around that I made into a couple of chisels about 12 years ago and with a water quench the stuff is harder than chinese arithmatic.

[pkrankow]

There is a set of instructions in an older text (c.1900) available online that boils down to forging a sample to near net shape, taking a "long" heat from overheated at the end to cold in the middle, quenching, file testing, breaking, then repeating at the determined temperature and drawing temper by running color in a similar manner. You can quench in air, oil, water, or brine to determine your best temperatures to quench from.

I just don't remember the text to reference and due to my regular computer dying I can't look through my downloaded books right now. Hopefully someone can point out the correct text.

Phil

[Shawn S]

I quench rebar everyday at work about every twenty five minutes and it cracks every time.

[bigfootnampa]

Well I would use an oil quench, as I have often done. Most rebar that I have worked with is low to medium carbon that I would estimate at around 1030 to 1035. As such it will make usable edges and I would not be hesitant to recommend such treatment for your knife. It will not be the best knife you'll ever make... but YOU will treasure it! I usually flame off my oil quench to temper... immediately after quenching. I will redip into the oil quenchant and flame off the oil film about 6 times and then cool and grind and hone the final edges. Leave your cutting edges about dime thickness until after quenching and tempering. This may not be optimal and your steel is not great, but such edges are pretty functional for many everyday uses! I often make them this way for use around the farm cutting baling twine, weeds, ice, etc.

[ThomasPowers]

I know that Las Vegas New Mexico has places where you can get an automotive coil spring and have enough *better* steel to make a dozen knives; Shoot I'll be driving through Las Vegas New Mexico in about a month on my way to CO for a week camping and forging and I can drop you off a couple of coil springs as I can find them or be gifted them for free far faster than I can use them. I should be there around lunch time on Aug 28. Where shall I drop them off?

[Rhettbarnhart]

I would use good steel but rebar is easy to forge and if u quench in water and skip tempering it will be decently hard one big problem is it rust quickly in my experience but I'm just a newb:}

[Steve Sells]

Most all steels will rust if left wet, and as you said, you have no experience. Skipping on the temper cycle is asking for trouble if it harden at all. Also water for a first attempt to quench anything is also also bad, read the HT sticky if you wish to know why.

[Rhettbarnhart]

Steve I am not recommending this just sayin wat I did and more experienced ppl can tell him more about it

[Perrin Aybarra]

Steve, would you mind posting a link to that sticky? I'm on the mobile version and can't seem to find it.

[r smith]

I get so tired of people whining about rebar. What type of rebar are you using- or do you know? Many types and qualities available- junk metal available for sidewalks is not the same as high strength or welding rebar that is much more controlled in its recipe. All of the info needed is on the bar- those letters and numbers are not random.
smith out

[Steve Sells]

near the top of Knife reference section http://www.iforgeiron.com/forum/151-knife-class-reference-material/

[ThomasPowers]

I would think that a lot of stuff that is welding "OK" would be guaranteed to be of lower carbon to NOT get HAZ cracking. I do notice that they tie a lot of the critical use stuff like interstate bridge deck re-bar which would lead me to believe that it might be a higher strength version. Unfortunately the use case is still for tough whereas knife alloys generally go for hard/brittle

[McClellan Made Blades]

I guess I'll stir the pot a little and go ahead and mention to the fella wanting the info, to google Super Quench, it is a combination of a lot of different house hold items, including dish detergent, that stuf that drys your dishes in the dish washer, get the generice version, etc, there is more to it, I would have to get up with Wayne Coe as he is the one thatgave ot to me, who ever, I never used it. There are many that swear by it.

I believe that if I am going to put my sweat, pain and pleasure into a blade, I will make something useable, maybe only worth being seen by me, as it will be ugly as sin! Remember this, there are many many different areas or skills, that you will need to put energy, time and of course money, into this obsession, why not make the best of each one, because each one will be lessons you will have to learn, that must be retained, I know you're trying to avoid burning the one piece of HC steel you have, I guarantee you just about everyoneon here can empathise with you, because we felt the same way at one time or another, but what was learned was to make a knife out of the best quality steel/materials you can get your hands on . Look at where you are right now, learning how to HT a steel that you'll NEVER USE a knife blade. Yep pretty much useless info, other than learning what not to do, which there seems to be so much more of that, than what to do! When I first started (only 4 years ago), I was trying to make Excalibur, or so I thought, I scraped piee of steel after piece of trying to make it turn out perfect. Never mind getting to the steps of HTing, or the wood working, learning handle ergonomics. I soon realized that I would have to take whatever MY BEST was and like it, or I would NEVER finish a knife. Once I realized that, I started seeing the places that were make it or break it for that individual knife, and adjusted my process to be able to finish it with out destroying it, fo rme it was taking it back to the grinder after HT, so I started finishing the blade all the way out completely hand sanded to 600 to a 1000 grit, of course once it comes out of HT you have to do that all over again, but sanding aint never hurt no..., killed no one, it hurt a many that has had Tennis Elbow flare up from hand sanding for hours on end.

Do your research, like Mr. Powers said he is getting coil spring, great steel for making knives on a budget, (WHAT I mean is that while it is good steel and if you have a ton of it you can dial in every nuance of the steel, learn every aspect of it and be able to make a good knife, I feel like to make great knives you need to start with great materials, now I'm not talking about Buying CPM154CM or anything else fancy, you'll soon learn that you can make an exceptional blade from 1084, that was made for KNIFE MAKING! Contact Aldo Bruno for his 1084FG, can't get any cheaper than that, makes a great knife that can perform better than some better quality steels) easy to HT in a forge or with a map torch, Oxy/act, whatever you have that will get it to non magnetic, quech in oil and Temper, your process here may take some learning so hope he gets you A LOT! There are even lessons to be learned just heating the stuff up and hammering out into a bar. If you love to learn new things, then congratulations you hit the jack pot on a skill tha requires you to learn more stuff to have fun than probably anything else i have ever heard of, and it is THAT challenge that makes all crazy to figure out how to do it better everytime we light a forge!

There now you'll be thoroughly confused, my advice finish out the rebar, just to get a feel for whatever it'll be with out using up too much of your resources(cash), then work toward better quality steel, that way when you hit it just right, you will have something you can test, that starts another epic journey! Rex

BTW sorry fo rth eTypos, at work gotta go!

[ThomasPowers]

"Free material" can be very expensive it it won't do what you need it to.

In the scheme of things the amount of time it makes to do a blade---especially by hand---is a massive overkill compared to the cost of the steel you are working on. It behooves you to get the best you can. I suggest automotive springs, new where possible, as they generally are a decent steel easily worked by a beginner.

[FredW]

Most of all have fun.  Try the superquench, may do the job for you. And go ahead use the cheap steel if you like. One thing you will learn from that is hammer skills, which is very important. I also used cheap steels when I first started, never sold any, but was sure fun to do. Carbon steel is not that expensive but can add up fast when learning something new. Also, if you are like me and live in a rural area, the shipping cost can be more than the steel. Fastenal here also sells some tool steels, though you are going to pay more than you would if you purchased it from a steel supplier, but there aren't any shipping cost to speek of. Once you get the hang of using the hammer and other tools then use the better steels. Just my opinion and I am in no way as experienced as these guys. I see nothing wrong with using the rebar either, no different than using the RR spikes. Now pay attention to these guys on here as they are a wealth of information and will make the learning curve much less pronounced.

 

Fred

[Evan m.]

Not tempering rebar is not as bad as people think. Because of its low carbon content it has a lower max Rockwell hardness and is less likely to crack even when not tempered. My suggestion is selective hardening where you only harden the edge of a knife and leave the spines soft. This is a great technique that's used when metal quality is low. 

 

Edited May 30, 2017 by Evan m.

[Charles R. Stevens]

Depends on the rebar, bridge and high rise scrap bar is very different from the elcheapo 1/2" bar from th home center. Much of that cheap bar coming out of Mexico can get very hard. You realy don't know what is in it, as long as it meets minimum specs for tensile and shear strength it's good rebar, if it exedes it because of high carbon or high aloy scrap being in the mix the manufacture doesn't care. Same with A36 "mild" you can drill 3 holes in the same bar and one will dull your drill. 

Best you can hope for is that a peice from the bar will have close to the same composition and you can experiment with it. Baring that edge quenching in tallow, lard or bacon grease, or full quench in oil are about the safest. If it dosnt get hard enugh then try water, if that don't work it's super quench. 

Same for tempering, you have to experiment. A 400f toaster oven, to hard? Try 450f, ect. If going old school the. A red hot block allied to the spine and watch the colors run. Creep up on it. 

Edge quench or Differential tempering with a hot block will generaly let you get buy with a harder edge, but it's all guess and buy your faverite deity with out a known steel or testing what you have.   

[ThomasPowers]

Also look up tempering tongs.  I was able to buy a pair at a local fleamarket as nobody knew what they were and so the price was under US$10...