Just starting, questions on forge size and steel type

[bornofmud]

Hey guys, been doing a ton of research on knife making again and think I'm ready to actually give it a go.  i have several designs I'd like to try to make, and figured I'd go the stock removal method as it's a process I'm more familiar with.  the designs all fit inside of 2x11" and generally have 5" handles and 6" blades.

My first question (series haha) is, how much forge do I need to heat treat a 3/16-1/4"x2"x6" blade?  Can I get by with a two brick forge and a benzo torch?  Would also eventually like to try forging, would it be realistic to make an inexpensive first forge that could handle both? Can you even get forging temps from a propane torch?  Two of them?  Would love some recommendations here on approximate size and materials.

The second question is, for a larger hunting knife like the ones i plan on making, what steel would you recommend for a backyard heat treat?  I was going to use 1084 and heat treat just with a torch in open air, but decided the blades I wanted to make were too big for that.  Ideally I wanted to use 5160, as it seems a good choice for a heavy use knife, especially a larger one.  Can I get more out of 5160 with simple heat treating methods in this application, or should I stick with the 1084 for ease of heat treating?

[lytefoot45]

born, I've noticed your question has gone unanswered for several days so I thought I'd jump in and offer some assistance. Please remember that I'm not an accomplished knifemaker but I've been lurking here and other knife sites for a long time. Hopefully after I make an attempt to answer your questions someone else will chime in with answers that will help us both.

The amount of forge you need is, of course, dependent on the size of your work. I believe there are plenty of makers out there using the two brick forge with great results so it is certainly an option. Most of the experience makers are going to caution about getting hot spots with this type forge since your work will be so close to the burner. And, yes, you can get forging temps with the benz torch, but you are probably going to get frustrated with its limited capabilities if you use it very much.

A blown forge is pretty easy to make and use.  You should have seen plenty of sources for design during your research. I have made a couple of them that I believe work much better than the two brick design. One uses two coffee cans mated together. The other is made from a mailbox. There's plenty of info on the knifemaking forums about this stuff.

As far as back yard heat treating, you really can't go wrong with 1084. It is supposed to be very forgiving of the mistakes we newbies commonly make. If you notice, some of the big names use it for all sizes of knives. 5160 is a very good steel and you can certainly heat treat it with back yard methods. Karl Andersen uses it almost exclusively (But NOT in his back yard!). But starting out, you would probably be better served sticking to 1084.

Neither steel is overly complicated to heat treat, but using a torch is tricky. I watched Jerry Fisk use a torch at a hammer-in in NC and decided I'd stick to using my forge. I just don't need more than one hot thing in my hands at a time.

For more info on the different steels and their traits, search for info by Kevin Cashen. He has put TONS of information in cyber land about steels.

Good luck!
Wayne

[gudspelr]

Looks like you got some decent advice above. Honestly...I don't think you'll go wrong using either 1080/84 or 5160. 5160 doesn't need quite as fast a quench as a 10xx steel so if you're worried about quenchants, you could start there. When the heat treat is done well, any number of steels will serve you well, including the ones you mentioned.

As for forges, you're going to have to make some decisions. How interested are you in knife making is a question to consider. I say that because if you're going to continue on, you're likely going to want a decent forge before long. I haven't used a 2-brick forge, but I've seen many posts on/about them and imagine it could work well. But with a bit bigger forge, you can do a lot more.

You can also successfully heat a blade using a torch, then quench. That being said, you can also mess stuff up in a hurry. I used an O/A torch in a class with a master smith and it worked well. But, I don't use mine on my own here at home. I'm just a bit too nervous about not getting an even temp throughout, etc.

It's an incredibly fun and addictive hobby. As soon as you see how you can manipulate steel when it's hot....you just want to keep trying stuff    . But don't feel like you have to shell out a ton to get started. If you can get into it by stock removal with the tools you already have, then jump in.


ETA-

Figured I'd put in a couple pics of the forge I ended up making when I started. It's not ideal and I'd change some things if I was doing it again, namely the size-it's a ways too big. As was mentioned above, there are forge designs and info on the web on several different types if you choose to go the direction of a bigger forge than a two brick.

 

 


Jeremy

[kbaknife]

The answers to your questions would literally fill volumes of leather bound books.
But I will add this to the information given:
Don't just build the "two brick forge and a benzo torch" type forge. It truly is as close to worthless as you can get.
Build a blown vertical forge. It's just not that difficult. And as your experience increases, you will already have the ability to do more and more without then building another forge. You'll already have it.
It will assist in heat treating the blades you mention and allow you to forge and heat treat larger blades in the future.
They're pretty simple to build - some of them only appear complex.

[bornofmud]

Wow, thanks for the replies guys, very helpful.  I continued researching after writing this, came across many of Cashen's posts, extremely helpful. I found a local source for firebrick and decided to give the two brick forge a try.  Just finished it yesterday.  I heated an old file in it up to non magnetic in about 5 minutes, the problem being that the non magnetic area is about  4-5" max before it tapers off pretty quickly to magnetic.

My plan for now is to get the next size up in torch (using a ts4000 I got for free, doesn't have any flow control and maxes at 6,300 btu/hr or something like that) and make due with this until I can build up enough money/parts to make a proper forge. The ts8000 has a flow control and maxes at 12,000 btu/hr which should increase the area I can evenly heat enough to heat treat the first chunk of knives I want to make.  I think I will find this brick setup frustrating enough that I will want something a little bigger and less hotspot-y pretty quickly. It will atleast get me experimenting and working on some knives.  Also, decided to go with the 1084, always more time to work with the fancier steels later, and I feel like I actually have some chance of getting a good blade out of 1084.  

Also been keeping my eye out for an old weber I could turn into a small charcoal forge.  Cashen recommended charcoal for working with 1084 if an oven wasn't available on the basis that it's easier to control and less hotspoty than a small gas setup.  Seems like it would be cheap to make so long as I didn't have to buy a new weber, fun too.  So may try that if the two brick thing really isn't working.

Thanks for the replies guys!  I'm sure it gets annoying typing out the same responses over and over, I know it can over on the bow making side haha.  Any other tips for a beginner are always appreciated.

[gudspelr]

Glad you got yourself going. Sounds like a larger torch might get you some more heat in the brick forge. The difficulty may be you'll end up with the same few inches getting non-magnetic and have difficulty getting a longer blade up to temp without over heating some of the rest of it. I'd keep your blade experiments with that set up to smaller knives.

I don't know where you live or your shop area, but a coal forge might prove problematic. It should be noted here that I haven't used a coal forge, but have seen them used and know guys who have them. You'll need a blower for it along with coal. I know at least here up in Idaho it's something guys have to get shipped in and you may have the same problem sourcing it? The other thing is while there are some definite pros (such as being able to heat specific areas and not the whole blade) but there are definite cons, as well. If you're in a subdivision, your neighbors may not enjoy the smoke. It takes longer to get up and going to begin forging vs just getting the propane turned on and lit. Again, I haven't used one, but I hear from everyone that there is a definite learning curve to controlling the fire for what you want when forging.

None of that is to say you shouldn't do a coal forge. They were used for a LONG time and very successfully so. If I was going to buy a blower anyway, I'd build a blown propane forge. As Karl mentioned, they can actually be a pretty easy design (do some searches on here with his name-some great pics of his and the designs). But you will need some tongs or a welder with some rebar or something for a handle. Dropping steel down into the bottom of the forge after spending all that time forging it can suck    .

Jeremy

[bornofmud]

Yeah, I was thinking that may happen as well, might try to close up half the front to try and keep the heat from rushing out so quick on that end. I made a pass through on the back of it too, so if I can consistently heat 5" and have the last 1" tip hanging out the back till I get close to non magnetic, I will hopefully be able to scoot it in and heat it quickly..  1084 doesn't show up for another 5 days and I don't have an anvil or hammer to try turning a file into a knife, so I'll just have to keep the experimenting to file shapes rather than knife shapes for now.

Don't think there's too much of a problem running a coal forge here, and I'm pretty sure I could source a blower, but if not I could always use a hair dryer. Does seem a little tricky to get to do what you want.  Cashen recommended building up a tunnel around the coals out of firebrick, and I've seen other folks use a steel pipe to ht in to give a more even temp along the piece you're heat treating. But yeah, it'd be more of a thing specifically for forging and ht'ing 1084, where as ideally, my next forge will be one that I could do most/any projects I plan on doing in.

[bornofmud]

Few more questions, does any heating over the 1500F point cause the grain to inflate?  Or is there a small window I have here?  How long do I have to get areas of the blade that have reached 1500F into the quencher? As in, if I heat up the first five inches to (ideally) 1500, then pull the knife back so the tip is in, the first 1" i heated will slowly start to lose heat.  Does the blade need to be at 1500 when it touches the oil, or does it just have to have gotten to 1500?  I remember reading that it takes longer after a blade has reached non magnetic for it to cool enough to become magnetic.  Is this my window for when I have to get it into the quench?  Before it becomes magnetic again?

Oh!  Just had an idea, if I got the other torch, could I set up one blowing into the front entrance and one through the hole in the side?  Seems like that would give me an extra couple inches of potentially even-ish heat. The pass through on the back is pretty big, so I think it'd still have enough ventilation. Any ideas?  Safe to try?

[Lin Rhea]

Nicholas,
          I have had a lot of stuff that I have cobbled together when I first got started that I have thrown away or are still taking up space. How I wished I had saved my money and had listened to those who knew!

I want to encourage you to avoid making anything potentially dangerous, number one. The use of oxy/acetylene and propane and fossil fuels are cool but need to be handle carefully.

I feel like I must also encourage you to take a class or to get with someone who already has the type of equipment you plan to use and spend time in their shop. Your mind is your most important tool and any money spent up front should, in part, be going toward training.

This forum is a great tool for learning, but I sometimes wont comment about methods that I don't use myself. There may be two reasons why I don't comment. I don't know much about that method OR I don't think it's a good method under the circumstances and I don't want to seem like I am encouraging the question asker to go ahead with it.

I have seen some very good advice above about forges and some pictures to go along with the advice.  I recommend that you re read that advice and follow it. Brick forges mostly are unsatisfactory and combining them and Oxy/Acetylene torches will lead to problems or worse.

If you get your steel up above 1750-1800 degrees in Fahrenheit the grain will get bigger, sure nuff. But if you are going to forge your steel, you will have to get it up to that temperature and maybe some what hotter. It has to be hot to move it. After the forging is done, Now the question is can you reduce the grain back down to a size that is small (which equates to a tougher state) and keep it from ever getting it above that temperature again?

It's not clear to me from what you are saying if there is perhaps there may be some confusion as to what some of the pertinent key factors of heat treating and controlling grain size are. Forgive me if I am wrong. But if there is some confusion, it makes the point that training is more important than the tools.

That said, I would like to see you make a forge exactly like the one Karl describes.

[bornofmud]

Yes, I would love a proper forge, however the investment to get started is about 5-6x as much, and the reason I have put this project off for the last year is because it feels overwhelming to start off with a 500$ investment just to try something that I've never tried before.  I will learn plenty from my two brick forge between now and the time I can save up and source the parts for a better forge.  

I appreciate the input Lin.  I have seen many, many build alongs and pictures of peoples forges, I am not confused as to how to go about building one, but was wondering if my two brick setup would work for simple heat treating of simple steel.  I ended up making it and finding out for myself.  I am not using oxy torches, or even mapp as I see no reason why higher temperatures would help my mini forge, would just make the hotspot worse.  I was hoping the larger benzomatic would push a larger volume of propane, and thus fill more of the chamber.  If it still didn't, I was wondering if it would help/be safe to setup a secondary propane torch blowing into the entrance.

My questions on the temperatures and grain size were about heat treating, not forging, I know that you must get the steel hotter than 1500 to forge and that it will blow up the grain size, and that you must go through thermal cycles to get it back down before hardening. I was asking how much play room there is when heat treating. For example, if I heat the blade to 1575 in some parts, is it going to make a distinct difference in grain size in those parts?

The other question was how long can the blade cool before needing to quench.  As in, how much time do I have to pull the knife from the forge and stick it in the oil?  Do I have until the knife becomes magnetic again?  I know that once it's in the quench, 1084 has to cool to 600F(?) in one second, but what temp must it start the cooling from?

Also, just did another test run on a file.  Was able to get a good 5.5-6.5" non magnetic all at once by constantly moving the file back and forth rather than letting it sit in there.  Thinking I'll be fine for these first few knives, might still get the bigger torch just to make it easier, would be nice to be able to lower and raise the flame.

[Lin Rhea]

You have to go from the forge to the quench pretty fast but its done every day. If it becomes "magnetic" again, it's too late and you must heat it again to the critical temperature.

Once you have the grain reduced, The grain wont grow unless you get it above 1650 or so. The key to even grain size and even depth of hardness is naturally EVEN HEATING. Evenness is the name of the game. The bigger the forge and the closer to the critical temperature that the forge can run (ideally just above critical), the easier it is to heat a blade evenly without over heating it.

Your last question needs more explanation.

[gudspelr]

You've got some great info above.

I can understand the whole money thing, I was there at the beginning, myself. A member on this forum actually invited me to his place for the weekend. I drove the 6 hours and got my first exposure to forging and we made my first knife together. It was fairly rushed and very basic, but I learned a ton. I've been to several maker's shops since then, taken a week long class, gone to a hammer in, etc. All of those things have helped me IMMENSELY. More than any tool I've made or paid for.

All that to say, if you have any willing maker somewhat nearby, it'd be more than worth it to look them up. Seeing how others do their heat treating, how they have their shop set up, what's used most and how to use the tools can greatly help you in deciding how to move forward.

Be safe with what you have already and learn what you can. You may well have trouble getting the even heat Lin already spoke of. But, you can do some testing afterwards and see how it all went. In regards to setting up a second torch at the opening, I'd seriously discourage it. Do your best to deal with one significant heat source. Trying to pass hot steel back and forth next to a second torch gives me the willies....

Jeremy

[bornofmud]

Thanks Lin, that's exactly what I was looking for.  As to the last question, I have one torch blowing in through the little port on the side of my two brick forge.  It makes a bit of a hot spot in that area (bout' 2" diameter).  I was going to get a torch that burns about double the volume of propane as the one I'm currently using (~12,000 btu/hr as opposed to ~6000) to help will more of the chamber as there is a good 4-5" at the mouth that don't get very hot. If that doesn't work, I was wondering if I could take my 6000 btu torch and put it at the mouth of the forge (with the other torch at the port on the side) to make more of the tube functional.  

though after the last test I did, and the fact that I can get by being about 100F over and not ruin the blade, I'm pretty sure I'll be fine without two torches.

Thanks Jeremy, didn't see your post till after I replied.  I'll hold off on the two torch thing.  Will look into finding a maker around here, I'm sure there's atleast a couple.

[gudspelr]

Just found this thread that at least may give you some, ideas for planning down the road. Some good info and pics for anyone thinking about a forge.

 http://tradgang.com/noncgi/ultimatebb.php?ubb=get_topic;f=110;t=001246;p=1


Jeremy

[bornofmud]

Nice, thanks, thinking that a 12" vertical forced air forge would do the trick for any blade (or most else) I'd want to do.  Need to find a parts list for the blower/propane setup.  Hopefully have one built before Feb.

[Lin Rhea]

I cant answer that question without saying this: If you can heat it evenly, it will work. If not, it wont.

I haven't used that type of set up so I cant really know.

[hickstick]

here is my first 2 brink 2600deg soft fire brink forge:

 

cut one brink in half the rasped the tube down the middle, then used refractory cement to stick it all together....

 

the firebox is just a bit too big to get a good heat with a torch:
 

so I ended up building a forced air burner out of 1 inch steel pipe and cast fittings and hair dryer (then a bathroom fan...then a real blower..lol)

 

ended up building a vertical forge out of a dollar store stock pot and inswool and used my 1 inch burner.

 
you can see the firebrink forge on top of the stock pot.

[hickstick]

the stockpot forge gets hot enough to weld but just barely.

 

I've made a new burner out of 1.5" pipe but haven't forged in a while so I don't know how hot it will get.