Frustrated with 2-brick forge

[ohaple]

So I have been working on getting into knifemaking. I have basically completed a few fixed blades and a few folders, but need to heat treat them to finish up. I read just about every article I could find on one and two brick forges, but still was not able to heat more than 1'' of blade to critical temp. I assume that this is only from it being heated directly from the flame. I started on my smallest blade to try it out, and am disappointed that a 4'' x 1/2'' x 1/8'' blade would not heat up in this forge. I figure the problem is most likely the design of the forge or the quality of the propane burner. Any advice appreciated. Also, how far into the hole, if at all, should the tip of the torch be inside the hole? I put it about 1/2'' in when I did it.

I purchased a Bernzomatic WT2301 for my heat.
I got a few soft firebricks and carved out a small cavity, with a small port in back, a medium-sized port in front, and a small hole top-center for the torch to come in tangent to the curve of the cavity.
I wrapped it up in some chickenwire, got my oil and magnet ready, and started it up. I let it heat for a couple minutes before starting on a blade. After about 10 minutes in the forge, I could not get even half of the blade to be orange.
My lighting is low, as recommended, so I can tell to color better (though I am using the Curie point more than color, and only using color to tell which parts are hotter than others).
I tried multiple positions of the blade in the cavity. With the blade int he middle or bottom of the cavity, it barely heated at all. It only would get near critical when held at the top, in the path of the flame.

Here are the pictures of the setup and the tiny blade that I was unable to heat treat with it.

Again, this blade is about 4'' x 1/2'' x 1/8''

 

[JTknives]

I think your biggest problem is shear lack of BTUs the torch puts out. Most torches put out 2000-5000btu and that torch looks like a lower BTU torch. Looks like you have maybe a 2" diamater chamber that's 6-7" long that's most likly 20 cubic inches of volume. On Forges 450 to 500btu/in^3 is considered minimum for forge weld. So say you need 300btu/in^3 to hit your 1500 deg mark. That would mean your burner would need to put out 6000 btu, there is no way. Easy test is run the torch on high and time how long it will run on a 1lb cylinder. 1lb of Propane is 21,600 btus.

 

[LCoop]

When I made mine torch hole entered BOTTOM of cavity with a trough under blade so flame could circle knife steel. It definitely got hottest at flame so would "slide" blade steel in and out of flame. Could easily get nonmagnetic entire blade this way.

 

[tattooedfreak]

I made a coffee can forge which is basically the size you have and had no problem. It could be your nozzle itself. you need a more open torch, not a pinpoint one. Also, angle the nozzle so it doesnt enter straight and will allow a venturi effect (circle around the interior), it shouldnt enter the forge body, just barely poke inside.

 

[Atlas Knife Company]

First, that's a bad design of 2BF(two brick forge). This design is much better:
http://www.bladeforums.com/forums/showthread.php/920120-Virtual-BBQ-2-Brick-Forge-WIP

Second, your torch is definitely an issue. If you want to stick with a factory made plumbing torch, this is the best you can get. I've tested probably 15 different models, and this one is hands down the best:
http://www.menards.com/main/tools-h...438807024-c-10163.htm?tid=7738531891447546977

You're much better off with a 30k BTU burner. Here's a link to one specifically made for use in 2BF:
http://www.atlasknife.com/atlas-30k-burner

No one else, that I have found, makes a burner this size. Most start around 75k BTU and are really too heavy/bulky to work well in a 2BF. Kind of like using a fire hose to wash your dishes.

 

[Kevin McGovern]

as others have said, the torch is definitely an issue. I have a coffee can forge with the opening for the torch at the front pointed toward the rear. I let the forge heat up with the torch in the side hole. towards the end, I will hold the torch in my hand and move the knife and flame to make sure the blade is fully heated evenly. Here is the torch I use: http://www.harborfreight.com/propane-torch-with-three-burners-91899.html

and here is a video of my forge running. this works very well for me at the moment. [youtube]wET_PkPG7KE[/youtube]

 

[ohaple]

First, that's a bad design of 2BF(two brick forge). This design is much better:
http://www.bladeforums.com/forums/showthread.php/920120-Virtual-BBQ-2-Brick-Forge-WIP

Second, your torch is definitely an issue. If you want to stick with a factory made plumbing torch, this is the best you can get. I've tested probably 15 different models, and this one is hands down the best:
http://www.menards.com/main/tools-h...438807024-c-10163.htm?tid=7738531891447546977

You're much better off with a 30k BTU burner. Here's a link to one specifically made for use in 2BF:
http://www.atlasknife.com/atlas-30k-burner

No one else, that I have found, makes a burner this size. Most start around 75k BTU and are really too heavy/bulky to work well in a 2BF. Kind of like using a fire hose to wash your dishes.

Thank you for the comprehensive responses. I have read many of your posts on the topic and trust your advice. I don't mind being wrong on this since its still my first go. What is wrong with the forge design? I had seen your other design and figured it was more effort to make, but looked to have pretty much the same outcome. Though my hollowing isnt prefect, what would the difference be in hole-saw drilling through two bricks stacked like mine vs 4 bricks stacked like yours? Durability?

I figured the torch must be underpowered, but . Its been a bit of a challenge trying to get my whole hobby shop outfitted for a couple hundred bucks, and torches have been tough to pick when most consumer units don't advertise BTU. @Atlas_Knife_Company, in your experience does the MT245C get hot enough to heat treat blades? I am not looking to forge weld or actually forge blades, just to heat treat 1084 on my own. If the MT245C won't handle that then I will probably go with the atlas burner to be safe.

I appreciate the advice everyone. It is fun learning all of this and getting into it.

EDIT: found that a local auto shop has the MT245C in stock, so unless I hear otherwise I will plan to pick that up on my way home from work tonight. I will update you guys on how it goes.

 

[Taximanny]

I think creating a vortex within the forge is the key...
Getting the flame to swirl inside.
So an almost perfect circle is needed in the cavity.
Also the torch hole should be up and slightly back for this to happen.
Mine is open in the back but I put another firebrick in the back to adjust the heat.
I have also wrapped chicken wire around mine.
I have since got an Evenheat oven for my heat treating but still use this on occasion for handmade templates and the sort.
I can get 01 tool steel to cherry red in about 3 min.

 

[Kevin McGovern]

it appears the MT245c is a pencil flame burner. THIS IS NOT WHAT YOU WANT. It can get very hot in a small spot, but you need good btus via a high volume flame to heat up the burner cavity. if it says "pencil flame" that is not what you want. I believe the one you want is sometimes referred to as a "rosebud" flame. maybe a bernzomatic ts4000 would work? what are your options?

 

[Taximanny]

Here's a pic of the angle of the torch inside
Getting it set to where it is creating a vortex is just slight adjustments.

 

[aarongb]

it appears the MT245c is a pencil flame burner. THIS IS NOT WHAT YOU WANT. It can get very hot in a small spot, but you need good btus via a high volume flame to heat up the burner cavity. if it says "pencil flame" that is not what you want. I believe the one you want is sometimes referred to as a "rosebud" flame. maybe a bernzomatic ts4000 would work? what are your options?

Actually Atlas Knife Company is right about this, the MT245C is a great starter burner for a 2BF. The Benzomatic you mention doesn't even come close, and very similar to what ohaple tried originally. A few months ago I made a new Atlas-style mini forge, and bought the Atlas 30k burner, but still use my old 2BF and the MT245C for small jobs because it is so easy and works so well.

 

[Atlas Knife Company]

Leaving a small opening in the back turns it into a "chamber." Fully closed creates a lot of dragon's breath and doesn't get as hot. Fully open just lets heat blow right out the back. The reason I used the bricks cut in half is that it makes the whole drilling easier. It can be done the other way, but this way is easier. Lot's of people have forged and heat treated with the MT245C in a 2BF. I've tested the TS4000 side-by-side with the MT245C and found the MT245C to put out about 25% more BTU. But, if you want a trigger start, the TS4000 is decent.

 

[ohaple]

Here's a pic of the angle of the torch inside
Getting it set to where it is creating a vortex is just slight adjustments.

Thanks for the pictures and advice. I will plan to round the cavity more, right now it is mostly round, but is more of an oval shape.

@kdogmcg, the reason I was thinking of the MT245C was based on Atlas' recommendation. I agree that it says pencil torch, but I also trust Atlas' knowledge on small forge building. My options are pretty much open within reason. I am trying to keep it pretty cheap, so less than $100 for sure, less than $50 would be better though. But I am willing to order something if it means getting the right tool. If the MT245C works, it is attractive for price. I will be traveling by a harbor freight this weekend, so I will have the torch you got as an option as well.

The three choices I have seen recommended here that seem reasonable to me are:
-MT245C
-HF Chicago welding three-tip torch
-Atlas 30k BTU torch

Can anyone else weigh in on these options? I have at least 18 blades in the works, so switching off of 14oz propane bottles isnt a problem and may even be cheaper. The HF torch and Atlas 30kbtu have been confirmed to work by Atlas and Kdogmcg.

EDIT: you guys posted while I was still typing Since two of you confirmed the MT245C should work in a 2bf, I will plan to pick that up since it is cheapest and most convenient. Then when I get home I will re-carve the cavity to be more round and less oval.

I will be sure to update you on how it works. Thank you guys very much again, I appreciate the information and advice.

@Atlas, I will have to measure, but I think that the rear port is about 1'' square, while the front port is closer to 2''x3'', and the inner chamber is 3'' round.

 

[Kevin McGovern]

Actually Atlas Knife Company is right about this, the MT245C is a great starter burner for a 2BF. The Benzomatic you mention doesn't even come close, and very similar to what ohaple tried originally. A few months ago I made a new forge, and bought the Atlas 30k burner, but still use my old 2BF and the MT245C for small jobs because it is so easy and works so well.

Ah. I took another look at it. I was going off the "pencil flame" wording on the package. I was thinking it would be like the one he has currently. It does look like it is a good choice. Similar to the HF unit i linked to in size anyway. i can heat 1080 to orange in abut 4 minutes.

 

[Kevin McGovern]

Thanks for the pictures and advice. I will plan to round the cavity more, right now it is mostly round, but is more of an oval shape.

@kdogmcg, the reason I was thinking of the MT245C was based on Atlas' recommendation. I agree that it says pencil torch, but I also trust Atlas' knowledge on small forge building. My options are pretty much open within reason. I am trying to keep it pretty cheap, so less than $100 for sure, less than $50 would be better though. But I am willing to order something if it means getting the right tool. If the MT245C works, it is attractive for price. I will be traveling by a harbor freight this weekend, so I will have the torch you got as an option as well.

The three choices I have seen recommended here that seem reasonable to me are:
-MT245C
-HF Chicago welding three-tip torch
-Atlas 30k BTU torch

Can anyone else weigh in on these options? I have at least 18 blades in the works, so switching off of 14oz propane bottles isnt a problem and may even be cheaper. The HF torch and Atlas 30kbtu have been confirmed to work by Atlas and Kdogmcg.

EDIT: you guys posted while I was still typing Since two of you confirmed the MT245C should work in a 2bf, I will plan to pick that up since it is cheapest and most convenient. Then when I get home I will re-carve the cavity to be more round and less oval.

I will be sure to update you on how it works. Thank you guys very much again, I appreciate the information and advice.

@Atlas, I will have to measure, but I think that the rear port is about 1'' square, while the front port is closer to 2'' square, and the inner chamber is 3'' round.

yeah, whatever Atlas states. He knows his stuff.

 

[JTknives]

I have played with a few torches in my day and by far the most impressive is one I picked up from a pawn shop for a few bucks. It's a turbotorce STK-9 (sticker is warn off but looks just like the STK-9 in the picture) and the flame it emits is crazy. I took a few shots of the flame mine emits. First picture is the flame at a level where most torches run at, next picture is it cranked wide open. It's hard to capture it's full impressive flame with a camera.

 

[Kevin McGovern]

The video I posted has my torch running at no more then 1/2 throttle. It really cooks.

 

[ohaple]

Good news. The recommended torch (MT245C) works. It was enough to easily heat the entire small knife and the entire blade + 1/3 of the tang of a 3.5'' drop point hunter. Got them quenched and in tempering right now. Did the file test to confirm they got hard.

That was achieved without modifying the forge, but I see how making it more circular will allow me to get even better performance, so I plan to fix that this weekend.

Thank you all again for the advice. When I finish a couple blades I will be sure to post them on BF so you guys can see, but here is a sneak-peak on a few with the blades unfinished. The strange looking tangs on the folders are actually pocket clips. I had never seen anyone do it, so I figured I would give it a try.

3'' Friction folder with a grenade-pin style lock, magnetic retention, and a pocket-clip tang. Purpleheart and canvas micarta with black g10 liners.

3'' Friction folder "pen knife," intended to be smaller than a sharpie and look like a pen when in-pocket. Maroon micarta. 0.8oz

My first attempt at a stick tang blade with a guard. My technique on this whole style needs a lot of work. Leopardwood handle.

 

[Gabriel Kierulff]

I think creating a vortex within the forge is the key...
Getting the flame to swirl inside.
So an almost perfect circle is needed in the cavity.
Also the torch hole should be up and slightly back for this to happen.
Mine is open in the back but I put another firebrick in the back to adjust the heat.
I have also wrapped chicken wire around mine.
I have since got an Evenheat oven for my heat treating but still use this on occasion for handmade templates and the sort.
I can get 01 tool steel to cherry red in about 3 min.

did you drill this holes yourself or you bought the bricks already like this? If you drilled it, how did you do it?

I'm about to build mine, just bought my bernzomatic Ts4000

 

[mwerner]

I'm working from the design from "Gough Custom" channel on YouTube, and he recommends using MAPP gas and the Bernzomatic head with the air intake towards the bottom of the tube.... You don't want the air intake near the head as this will "recirculate" the hot air from your forge.
He angles the hole for the torch from the front, slightly back and "up" to create the swirl..... Appears to work very well in his videos.
(Sorry, cant post the URL on YouTube from my tablet...)