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Charcoal Forge: Laying steel plate or refractory brick on work piece.


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I built a charcoal forge and used it for the first time today. I have no experience and am looking for a way to harden some knives I made.

I stuck an old file in there to see what would happen and got it to a bright orange color. It wasn't uniform though. I laid a 1/4" piece of black, but very hot plate steel on the file. I took a look after a minute and the whole file was a uniform bright orange color where the plate was.

What did I do? Would laying a roughly knife sized steel plate or refractory brick on a blade help with even heating?

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Some people put a tube or a piece of angle iron in their forge and that helps the steel inside to get a more even heat. This takes a lot of heat to do though. I'd just say learn some forge maintaining skills and if you move the blade slowly back and forth in the hot spot it will eventually get up to a nice even heat. 

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IDF&C is probably right. It is very easy to be a little stingy with fuel when you first start using charcoal. You need about four inches of fuel on top of the stock and about three below in my last forge. 

 Awrksmonkey is making a good point too. Most forges don't have a large enough hot spot to just lay the stock in and get it all to a uniform heat. Most charcoal forges can heat around 4 inches at a time so you have to pass the length of the blade back and forth through the heart of the fire. 

This is the way my lastforge behaved. Without pics and size of tuyere depth of firepot etc. it's a little difficult to give any more specific advice.

Pnut

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52 minutes ago, Irondragon Forge & Clay said:

Pictures of your set up and fire will help. You may not have a deep enough fire.

Try not to laugh. Along with learning how to make knives and operate a forge, I’m learning how to weld. I cut the pieces from a plate I was using for a weld bench.

She’s 9” long about 6” wide. It’s 5” from the tuyere to the top. The pipe is 3/4”. I sliced an opening in the pipe that runs the length and is as wide as a cut off wheel for a 4 1/2 angle grinder. The pipe is underneath 2 pieces of 1/8 x 1” bar stock welded at 45 degree with less than 1/4” gap for air to get through. It’s lined with cat litter, sand, grass clippings, and ash. It’s already crumbling but I got to make steel change colors.

I had my heart set on a frosty burner and a small propane forge. The cost of insulating materials and tools needed made it too expensive for now. 

When I did the plate on the file thing I was burning the last bit of charcoal. Only half the file was in the forge and it was at a 45 away from me. It was resting on a pile of fully lit coals at the same angle. 
 

My fire maintenance technique is similar to watch burgers cook on a grill so that’s my next research assignment.

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The first problem I see is the hair dryer. Hooked up like that it will supply way too much air for charcoal. You need to have a way to lower the air blast to the fire. There are some ways documented in the forges section. One of the easiest is to have the dryer outlet about an inch from the tuyere pipe and only aim it at about half the pipe opening. You could also build an air gate to bleed off some of the air one of the neatest I've seen was made by jasent (I think) using an electric conduit elbow where he just rotated the cover to open up the air or close it for more air.

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12 minutes ago, MJTX said:

Try not to laugh. Along with learning how to make knives and operate a forge, I’m learning how to weld. I cut the pieces from a plate I was using for a weld bench.

Don't worry, I'm in the same boat. Just starting to blacksmith, and just starting to weld. To be fair, I've wanted to do both for a long while. And I have a list of welding projects already that's surprisingly long. We've got to start somewhere, right? Sometimes knowing that you need to ask a few questions of people who know infinitely more than you is the best way through.

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What you have there could work pretty good if you do some tweaking. I'd suggest reading all the jabod posts you can starting with the pinned ones And the Tim Lively washtub forge post. 

I prefer a side blast set up like a jabod butyou already have the washtub configuration so I'd make that work or at least try before tearing anything apart. You probably have a little too much height from the top of the air pipe to the top of the forge but I'm not really familiar with washtub type forges. 

Pnut

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Fuel does not make the fire hot, air makes the fire hot.  

Fire fuel is not deep enough and way too much air.  The fire does not heat the metal, the metal in contact with the hot coals is what actually heats the metal.

 

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9 hours ago, pnut said:

What you have there could work pretty good if you do some tweaking. I'd suggest reading all the jabod posts you can starting with the pinned ones And the Tim Lively washtub forge post. 

I prefer a side blast set up like a jabod butyou already have the washtub configuration so I'd make that work or at least try before tearing anything apart. You probably have a little too much height from the top of the air pipe to the top of the forge but I'm not really familiar with washtub type forges. 

Pnut

I was inspired by the Whitlox forge and the Lively forge. I missed the Q&A session Lively did a few days ago. I'm going to rent his video on Amazon soon, probably today. Before I welded up the vertical parts it was less than 3" from pipe to the top. I read that 4" should be the minimum so I made it 5". It would be easy to notch out a spot in the middle of the short verticals. I was thinking of adding a work rest of some type too.

I'll do more research and check out your recommendations.

Thank you for your help.

 

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Witlox and lively forges aren’t the most efficient designers for charcoal. The Japanese  style forge is much more efficient. How long of blades do you need to heat? 

Mu suggestion is to build a strait sided trench 4-6” wide and twice as deep. A tuyere down one side instead of the bottom seems to work best. Build a manifold with 3/4” schedule 40 tuyere every 6” (so a foot long needs two) angled down about 5deg. Into the trench. Each end will be cut away allow you to insert your stock into the center of the fire (4-5” of the bottom of the trench) expect to regulate the air to creat a fire just above your quenching temp and heat slowly. No need for welding temp. 

This will save fuel, creat less fire fleas and creat an even heat.  Inserting a pipe or heavy wall rectangular tube is useful for finer stock. 

 

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10 hours ago, Charles R. Stevens said:

Witlox and lively forges aren’t the most efficient designers for charcoal. The Japanese  style forge is much more efficient. How long of blades do you need to heat? 

Mu suggestion is to build a strait sided trench 4-6” wide and twice as deep. A tuyere down one side instead of the bottom seems to work best. Build a manifold with 3/4” schedule 40 tuyere every 6” (so a foot long needs two) angled down about 5deg. Into the trench. Each end will be cut away allow you to insert your stock into the center of the fire (4-5” of the bottom of the trench) expect to regulate the air to creat a fire just above your quenching temp and heat slowly. No need for welding temp. 

This will save fuel, creat less fire fleas and creat an even heat.  Inserting a pipe or heavy wall rectangular tube is useful for finer stock. 

 

My blades are very small. 4 or 5 inches of actual blade at the largest . I cut them out of knife stock with a hacksaw and file them by hand.

I have never looked into a Japanese style forge. A very brief search after reading your post shows very large and involved setups. 

I’ll look into them further but do you have any suggestions for a simpler version or a direction to point me in?

I am fascinated by Japanese culinary knives and would love to be able to make something similar someday. My main knife project is a Santoku inspired chef knife for my daughter. I’m trying to learn heat treating with some of the other knives I have made before putting hers in the forge.
 

Thank you for your help.

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On 4/16/2020 at 8:38 PM, Charles R. Stevens said:

Witlox and lively forges aren’t the most efficient designers for charcoal. The Japanese  style forge is much more efficient. How long of blades do you need to heat? 

Mu suggestion is to build a strait sided trench 4-6” wide and twice as deep. A tuyere down one side instead of the bottom seems to work best. Build a manifold with 3/4” schedule 40 tuyere every 6” (so a foot long needs two) angled down about 5deg. Into the trench. Each end will be cut away allow you to insert your stock into the center of the fire (4-5” of the bottom of the trench) expect to regulate the air to creat a fire just above your quenching temp and heat slowly. No need for welding temp. 

This will save fuel, creat less fire fleas and creat an even heat.  Inserting a pipe or heavy wall rectangular tube is useful for finer stock. 

 

Hello Charles and everybody.
I'm new to this forum and also new to blacksmithing.
I've just had the same problem with my forge. I've designed it for coke assuming that finding coke is easy however could only find good quality coal (low sulphur) and maintaining an even fire with coal is another craft I don't have yet. Now I'm using my forge with charcoal (from red oak) and realize that the fire depth is not enough and as you mention tuyere at the bottom creates lots of fire fleas (hope we speak about the same thing). I have plenty of firebricks and refractory cement. Would it be a good idea to put two rows of brick around the fire pot (but keeping an access to fire) to deepen the forge? Or just build another forge from scratch?

Thanks

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That is an exile to design for coal and coke, it will be a fuel hog for charcoal. Yes deeper will help, but bottom blast forges just aren’t efficient charcoal forges and electric blowers typically ply way to much air. Try opening the ash dump to waste some air, experiment with some damp subsoil to form a narrower fire bowl with high sides.

A coal forge is banned against the unburnt fuel and the green coal closest to the fire cokes. Charcoal can’t be banked as all of it will catch fire, so you will have to use dirt or as you suggest plate steel. I melt hard fire brick so I wouldn’t use it. 

My suggestion after experimenting with dirt would be to cut two plates the length of the fire pit and twice as deep, cut them so thy fit the pot vertically about 4” apart and connect them with a 2x4 strip at each end. Thus a box that you can fill with charcoal.

remember the air control. Making your own charcoal from construction lumber cutoffs also helps, as you only use fully pyrolozed charcoal and it generates less ash. 

Now if you fabricated that sweet forge yourself I would just build a side blast pot 

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After my first post / question above I made a deep dive into this forum and have seen many design errors with my forge :) 
There is a sliding valve after the blower, to be able to limit the air flow, however, air blast direction must be changed. I have seen that Japanese charcoal forge designs, tuyere pipe makes approximately 30 degrees angle downwards and connects the forge wall horizontally. 

As "Irondragon ForgeClay Works" mentions, charcoal size must be smaller. Wallnut-peanut size would be better. I've learned from the forum that the iron I'm trying to heat needs to mate not with the flame but with the charcoal itself. So smaller size is better, it means more surface contact.

Answer to "Irondragon ForgeClay Works"'s question, air gate valve can be shut off completely as needed. It is an easy to operate valve and I shut it off just before working on anvil. And thanks your compliment for the forge. 


Charles, I'll completely change the design.  As you said, air direction is so wrong for charcoal ( and especially charcoal that big) almost all the ash gone with the air. After burning around 20 kg's of charcoal in a batch, just a handful of ash piled in the ash gate :) 

And Ok, I forget that firebrick issue. At least bricks won't have a direct contact with the fire.  I'll build the new pot with 10mm steel (3/8"). Deep enough to accommodate enough properly sized charcoal. Additionally find a speed controlled blower. Some designs reduce the tuyere pipe diameter by half where pipe just enters the pot, to increase the air speed. Would you recommend this?

Thanks everyone for advices. 

BTW, 20kg of charcoal for forging/bending 54 pieces of holdfasts from 3/4" St-37 steel. I have no idea if this amount of charcoal is to much for this project. 

 

 

 

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