Increasing the capability of my two brick forge

[milkbaby]

I am using a two brick forge with Bernzomatic handheld torch for heat treat of stock removal kitchen knives (1084 or 15N20). It's two bricks one on top of another with the center of each hollowed out to form a cylindrical chamber all the way through. Here's a pic of my HT setup:

It was working nicely with just the handheld propane torch (angled in and up a bit to help swirl in the chamber), but then I made some blades taller from the edge to the spine and had to increase the size of the chamber. Unfortunately, I kept the chamber shape round instead of making it oval, so the heat retention seemed to drop quite alot due to the enlargement. I added a third firebrick lying in the back to block half the opening which kept more heat in but still allows a pass through to avoid overheating the tip.

I profiled and ground out a nakiri (Japanese veggie cleaver) with blade about 7 inch long and over 2 inches tall and tried to normalize and heat treat in my forge with MAPP/propane but couldn't get the entire blade mass evenly heated. I'm satisfied to edge quench, but it would be nice to do descending heats on the entire blade to normalize and have good grain, right?

What's the relatively cheap backyard solution? Extend the chamber with more firebrick: cut in half and hollow out my third brick? Have another torch blowing in from the front of the chamber? Get a big harbor freight torch to use with a BBQ propane tank? Problem is I'm not much of a fabricator, I basically have my hammer and hacksaw, LOL.

A semi-complicating factor is I'm an apartment dweller who needs to be able to have small stuff that I store inside my apartment and move out to my balcony porch only when working on knives.

 

[rjedoaks]

Atlas sells a small propane burner for the Atlas mini that is very reasonable . Works perfect for a 2 brick forge. Connects to propane tank. Would give you way more heat. I enclosed mine in steel, but see no reason why you couldn’t use yours as is. Works very well for conventional knives. The largest being 10x1 3/8 3/16 camp knife that I have used it for. Rich

 

[E.Carlson]

You are kind of at your limits without building a larger forge or looking at an atlas or similar.
How are the bricks connected?
When I used a similar set up and was heating larger knives I found that you want to heat the handle/tang to a nice red befor flipping it around and heating the blade. This prevents the cold handle from sucking the heat from the rear of the blade.

 

[milkbaby]

Atlas sells a small propane burner for the Atlas mini that is very reasonable . Works perfect for a 2 brick forge. Connects to propane tank. Would give you way more heat. I enclosed mine in steel, but see no reason why you couldn’t use yours as is. Works very well for conventional knives. The largest being 10x1 3/8 3/16 camp knife that I have used it for. Rich

Thank you for the suggestion! That looks interesting, and I'll hit them up for some more info!

You are kind of at your limits without building a larger forge or looking at an atlas or similar.
How are the bricks connected?
When I used a similar set up and was heating larger knives I found that you want to heat the handle/tang to a nice red befor flipping it around and heating the blade. This prevents the cold handle from sucking the heat from the rear of the blade.

Thank you for the info! The firebricks aren't connected at all, there is no refractory coating on the inside, just using the inherent refractory nature of the soft firebrick. I haven't been heating the entire tang, just a couple inches of it or so, and it's worked for smaller conventional kitchen blades. I think the larger rectangular profile of this nakiri just overwhelmed the capacity of my forge as is. I think I'll try heating the entire tang next time I try something this large.

 

[daizee]

It's impressive how much you can cook in a 2-brick with a narrower oval chamber. But I think you're ready for your first real forge. The Atlas Mini (which comes with the aforementioned burner) is great, and you can move it around easily. I can harden up to 7" of blade in mine and it's way efficient with propane. I use a tiny little pancake tank that has lasted forever.

 

[Atlas Knife Company]

The MT245 torch from menards is going to be about the most flame you'll get out of a plumbers torch. It puts out around 4k BTU. My Atlas burner puts out 30k BTU, more than enough to forge weld with. I would definitely recommend wrapping hardware cloth around it to keep it held together. Eventually, the bricks will crack. As long as they are together, cracks don't noticeable affect the insulating performance.

 

[milkbaby]

The MT245 torch from menards is going to be about the most flame you'll get out of a plumbers torch. It puts out around 4k BTU. My Atlas burner puts out 30k BTU, more than enough to forge weld with. I would definitely recommend wrapping hardware cloth around it to keep it held together. Eventually, the bricks will crack. As long as they are together, cracks don't noticeable affect the insulating performance.

Thanks so much! I "built" my little two brick with a lot of ideas from your earlier threads testing out making your forge. I especially liked reading your experiments about where to locate the burner and aiming it to get swirl in the chamber. There's so much info on the internet, but nothing as well thought out and detailed as the things you wrote.

I'm probably gonna pick up your burner when I have some extra money to burn...

 

[Stacy E. Apelt - Bladesmith]

The good thing about switching to one of Charles' burners is that when you realize that a better forge is what is needed. You can build one from a 12" long piece of 6" pipe ( or anything similar) and some Ins-wool and satanite. The burner will work perfect on a small forge. The pipe can be scrounged. A 12X24" piece of wool cost $10 and 5# of satanite is $15. Add a little shipping and a forge costs $35-$40. Use the fire bricks to block the back and front off as needed.