Hi all, way back somewhere in the Cretaceous period, I did a little bit of forge work at high school, making, amongst other things, a fire poker that my mother still uses today. I enjoyed that but metal shop stopped shortly after that and I've not touched a forge since. I found this forum a while back and figured it would be fun to have another but life got in the way and a few more years went past until recently I decided to do something about it.

I've built a gas burner based on a 1" Amal injector and it works very nicely. Now I've picked up some Vitkas grade 26 soft bricks (I'm in the UK) along with a few hard bricks and I'm shuffling them around like lego to work out how to put them together in a suitable manner. I read Frosty's notes on burner to forge volume with a ¾" burner wanting about a 350 cu in forge volume. With the bricks I have, the following set up gives a volume of around 485 cu in which I figured would be about right for the 1" burner. It's a bit taller than I see many other forges but to make it wide would need a way to cantilever two bricks across the top and, while I could make that work with a bolt together frame, I expect that unless the bricks were really tight, you'd have a seam that I expect you'd get heat blowing through, which isn't ideal.

In the photo I'm using the hard bricks but I'd probably only use these for the doors and hearth at either end, the actual build would use the Vitkas soft bricks. Burner would go in sideways, based on a helpful photo Frosty posted in the burner/volume thread. I have a bunch of angle iron and threaded bar in the barn so have most of the bits I need to put it together, just wanted to find out if my plan was reasonable to start with or are there better ways to lay out the bricks for that volume of forge. 

Thanks.

Bonus forge burner photo

You can still make it wider than tall fairly easily.   Soft firebrick is easy to cut with a dull hacksaw blade or something similar.  So, you just need to create a small shelf in your vertical bricks for the horizontal bricks to rest on.   If you cut a half inch off the thickness of each of your vertical bricks on both ends to a depth equal to the thickness of the bricks then you won't have to worry about the bricks falling in and you'll only lose 1 inch off the width.   By using all thread and angle iron you should be able to keep everything together nicely.

Hope that made sense.   If not let me know and I'll try to sketch something out for you.

Happy New Year s--first,

I have used the Amal burner with great success. I used to use hard brick Forges for years, instead of standing up the brick for the side, lay it on it's side, 2 bricks long. Use the bricks like you have for the top. Cut a notch from 2 bricks, to make an opening in the side at center. This allows your Burner to go in the side. For Long pieces, I would aim the Burner in the end. Yea, I know some of the people here will disagree with me, But I 'know it works'.

Neil

Thanks for such helpful replies. So, let's look at this again. Buzzkill, if I go with your idea I'd end up with this placement, but with the top and bottom bricks inlet into the sides half an inch. I can probably do that neatly on the bandsaw.

That would give me, after the inset, a volume of 8x4x4.5" =144cuin or, for neatness 150cuin. 3 sets of those would give me 450, 4 sets 600, 5 sets 750.

Now a 1" burner seems to tie with 750cuin of forge volume, but that's a pretty big forge. I have a total of 20 of the IFB's so could build up to a 750cuin forge but I'm thinking perhaps a 450cuin version would probably be a better fit in physical size and the work I'm thinking of doing, at least to get started. Is there any reason to go for the biggest or can I just run the burner turned down a bit and just have the smaller forge. I was thinking a smaller forge would be more efficient on gas for starting out and I could always enlarge it later if this turns out to be something I want to pursue more seriously. 

Yes, I believe you got what I was saying.  If you choose to use your bandsaw to make the cuts, make sure it's a dull blade or one you are willing to sacrifice.  A sharp blade will become dull very quickly when cutting soft fire bricks.

As far as size goes, my recommendation is to build a forge as small as you reasonably can and still be able to do what you want to do.  Large forges with big burners require a lot more fuel (which of course translates to cost).  Generally speaking if you are working with hand hammers you won't be able to work much more than 6 inches of hot steel before it needs to go back in the forge.   If you are working with high carbon steel especially then the repeated heating can have a detrimental effect.  It effectively lowers the carbon content in the steel.  On the other hand if you have a power hammer or you are doing long decorative twists that require long sections to be heated then a larger forge may make more sense.

From personal experience and from what I've seen from most people on here, the tendency is to build a larger forge than necessary with the mindset of "better to have it and not need it" than the other way around.  I had that at first too.  Now I want a gas forge as small as I can get away with.   The nice thing about brick pile forges is that you can rearrange the bricks to get different shapes and sizes fairly easily, so you can experiment a bit to see what works best for you.

ah, best not use the bandsaw then, I put a new blade on recently and tuned it up. I've some cheap old hand saws that will do the job then.

The only power for my hammer comes from my arm  so yeah, small forge. I'd originally planned to build a ¾" burner but they were out of stock and I ended up building the 1" version. I should, perhaps, have gone for the ½" instead but we have what we have, I could always build another smaller one later. 

I think I might try the 300cuin version first and see how that goes, the Amal injector is very controllable so I'm sure it would be ok running at less that flat out.

I'll knock up a prototype in the next few days and be back with more questions I'm sure. Thanks for all the help so far.

Ok, cut the bricks for the forge. Not the neatest job but I'm sure when they're tightened up by the all thread and frame they'll hold together just fine. 

However, the volume ends up being 13.5 x 8 x 3  which is 324cuin, smaller than I was expecting, either I measured wrong or math'd wrong . That's a suitable volume for a ¾" burner so I'll just have to keep mine turned down a bit and see how it works. 

Now to sort out the frame and thread and bolt it together. Given the flatter wider shape, would I be better putting the burner in facing down or from the side, I've seen both varieties when hunting for designs.

Looks pretty good to me.  Let us know how it works out for you. With that one inch burner there could be an issue getting complete combustion before the flame hits another surface, but you won't know for sure until you try it.

If you find you need more height you could flip your vertical bricks around and cut new shelves a bit higher.  That would make your top horizontal bricks stick up a little, but it shouldn't affect the functionality of the forge.

Good Morning,

You will find that those bricks won't last long. They will break with thermo-cycling and just barely touching them. This is the School of Hard Knocks. Don't try to hold too tight of clearances, they need to expand/contract.

Good Luck, Neil

1 hour ago, swedefiddle said:

You will find that those bricks won't last long. They will break with thermo-cycling and just barely touching them. This is the School of Hard Knocks. Don't try to hold too tight of clearances, they need to expand/contract.

How well insulating firebricks stand up to thermal cycling depends on several factors. First, it depends on their rated temperature range; the higher the range the tougher the bricks. Secondly it depends on the manufacturer. Morgan bricks will far outlast no name brands. Then, how gently they are treated, how hot the forge gets, and whether or not their flame surfaces are coated. Finally, as you mentioned, they need to be cradled--not compressed against each other. 

Of course, there is a trade off between use length and extra cost/work to do all this... 

Ok, so I finally had some time to put a forge together, I'd be grateful for any critique. I ran out of angle iron so still need to make a bracket to support the burner in place but, other than that, I think it should work. I welded a frame for the base, just for things to rest in. I'm the world's worst welder so please ignore the state of the welds, it's amazing what a grinder can cover up  I'll add a couple of handles to the frame when I get more steel, so the whole thing can be carried/moved as needed. Nothing is bolted tight at this stage, just held snugly in place. There's room for the hard bricks to act as a back and moveable doors as well as a small hearth at each end. I'll pick up some more angle during the week and make the bracket for the burner and then I should be able to fire it up.

One question, should the end of the burner be level with the brick so that it's not extending into the chamber itself?

 

 

Back just a little inside the surface of the brick would be even better for a little bit more longevity of the burner nozzle.

10 minutes ago, Hefty said:

Back just a little inside the surface of the brick would be even better for a little bit more longevity of the burner nozzle.

That's great, thanks very much. I'll do that this week once I've made the support bracket.

If I recall correctly, there was a semi-recent comment about this type of forge: don't over tighten the rods, the bricks need some room for expansion. I'm being lazy in not chasing and linking the reference, so take it for what it's worth. I also do not have direct experience.

--Larry

Thanks Larry, yes I remember reading a comment about that. I've just snugged the nuts up so that nothing moves but not tightened it all down hard. The welded tray is only for the base to sit in and there's half an inch of wiggle room in that. I think it should be ok and I'll keep an eye on it as it gets it's first few uses once I've got the burner installed.

One minor issue is that a couple of your all thread rods will be directly exposed to very high temperatures.  That is going to result in the zinc being burned off the galvanized rods.  It may not be enough to worry about metal fume fever, but with that configuration and materials there will be some amount of zinc oxide in the air when you bring your forge up to working heat.

Other than that it looks well designed and constructed to me.  Can't wait to see what you do with it.

If you place the burner high up on a side wall and aimed at the opposite side wall, then you can screw its mounting plate unto an existing angle iron; this also provides the best positioning of the burner in a box shape forge.

 

Ok, so, latest update. Forge is complete.

I did a quick check on the burner and it seems to be roaring happily

However, when I tried to run it in the forge, it doesn't seem to want to run properly. When just fired you get the typical yellow flame but when I turn up the gas it spreads out all through the forge and out of the front, turning it up further just spreads it further. I've tried playing with the threaded piece on the injector to alter the mix but it doesn't do much. I'll try and post a little video and see if that will upload. I figured before I experimented further, I'd ask for advice in case there's something obvious I'm missing here.

 

 

On 3/3/2026 at 3:49 PM, Buzzkill said:

One minor issue is that a couple of your all thread rods will be directly exposed to very high temperatures.  That is going to result in the zinc being burned off the galvanized rods.  It may not be enough to worry about metal fume fever, but with that configuration and materials there will be some amount of zinc oxide in the air when you bring your forge up to working heat.

Other than that it looks well designed and constructed to me.  Can't wait to see what you do with it.

I did wonder about that, but I'll be using the forge in a barn so hopefully won't be much of an issue, I could always replace the all thread with mild steel thread if necessary. I'm thinking this may end up being a prototype to be developed further. I'm not totally happy with how it's come together but we'll work on getting it working and go from there. 

23 hours ago, Mikey98118 said:

If you place the burner high up on a side wall and aimed at the opposite side wall, then you can screw its mounting plate unto an existing angle iron; this also provides the best positioning of the burner in a box shape forge.

 

Typically, I've only just seen this now that I've done it differently. If I can't get this version working, I can move it to the side, I have a couple of spare bricks to replace the top one if needed.

ok, that video didn't work, here's a link to it. 

https://youtu.be/HVFKPCCz2sI

Hopefully someone like Mikey or AFB will be along shortly to confirm, but in my opinion the greenish primary, and long purple and orange tertiary flame envelop in your photo suggests that your burner is not inducing enough air even when it's outside the forge, so when you put it in, the extra backpressure is slowing that induction even more and you're getting super-rich flames. I can't see from the photo: what sort of adjustment is there for air intake, or gas orifice distance from the mixing tube? You need a larger air intake area, or a bigger distance between the gas orifice and the beginning of the mixing tube so that the speed of the gas stream has space to entrain more air.

Edit: I just watched the video - Yes, very rich flames due to nowhere near enough air being induced/entrained.

Ah, that gives me somewhere to start, thank you. The burner uses an Amal injector as shown below, the threaded ring changes the amount of entrained air so I'll open that right up and see what changes and report back.

 

I've just noticed the valve is on back to front, doubt it makes much difference but I'll change that later.

Might also want to check the size of nozzle fitted to the AMAL injector.
I got a couple of different sizes when I bought my 3/4" AMAL injector, following an experienced members advice.

One worked better in my Firebrick forge, but my later Oval blanket-lined forge ran better with the different different size.

Amal size their nozzles in a flow-rate rather than a hole-size way. Bit odd! 

thanks Tim, I'll have a look at what was installed, I only have the one jet that came with the injector.

According to the Amal literature, the max air induction is when the end of the knurled ring is level with the point of the set pin, which I've set, I've turned the valve around but there's no real difference. I'll add some pictures of the burner assembly so you can see how it's all built.

 

Also, I double checked and this is the ¾" version, not the 1" as I'd previously thought. Must have got confused by pipe diameter and throat diameter. might have to modify the forge size then but for now I just need to get the burner operating properly.

Good Morning Third,

I also have a couple Amal Burners, except my Firebox is greater diameter. After I got the Forge running, I tried adjusting the thumb screw and eventually moved it back to where it was when I received them from the UK. The tapered set screw holds the center thumb screw from moving. 

You have too much fuel going to your burner. Either make/get a smaller jet and/or adjust your line pressure town with your regulator at the Propane Tank, not the Needle Valve. You can make your own Jet if you have or have access to Jet Drills or small number/letter/Metric drills. I have all of these from when I needed to tune Weber Carbs. Drill a hole in center with a Lathe, then You can Solder up the Hole and drill a smaller hole. Now you can step up the Jet size until you are Happy. If you go too large, Solder it up and Drill again smaller. KEEP A NOTE PAD FOR YOUR CHANGES, then it is easy to know what to go back to.

Welcome to the World of Forgery!!  LOL

Neil

Thanks very much Neil, I'll start out with turning down the propane at the regulator and see how that goes and order a couple of smaller jets.

Here's some AMAL info from a 2019 post of mine:

Quote

The 3/4" Amal Propane injector came with a 110 size jet as default, but timgunnn1962 recommended the 90 jet as giving a better range in single-port forge applications, so I use a 90 jet which works very well for me.

I bought both jet sizes when I ordered my AMAL. Hope this helps.

Tink!

Edited March 11Mar 11 by Mod30
Remove @ name tag