New Welding Forge WIP


"The Montana Bladesmith"
I have repaired ALL the images in this thread! It took a while to find/upload/post them, but everything is back the way it should be.....before Photobucket messed us over! :)

Its time to build a new welding forge..... for several years I've been using a KaWool insulated welding forge, mainly due to the high cost of castable.... but seems I'm doing much more forge welding these days, and the lining only lasts a couple of short I'm just tired of repairing, and being down for a week until things cure enough to use the forge again. So, time to "bite the bullet" and spend the money on a forge that should last for several years.

First order of business is a "shell". My Pal Steve Kelly donated an old air compressor tank to me a while ago.....and its just the ticket for this project. 16" diameter X 24" long. First thing was to cut the ends out, and then split it down each side.......

I've been forging larger and larger billets, so I decided I wanted a "chamber" size of at least 16" long X 10" Wide. Since the castable needs to be at least 3" thick to perform well, the 16" compressor tank is just right. In order to achieve the distance I wanted, the tank was split lengthwise. First I build the openings of 3/4" X 6" A36, making the front door 10" X 4 3/4". This allows me to stack standard sized firebricks to make the opening smaller, or remove them to enlarge it.....depending on how large the billet is.

I also built a "back door" that is 5 1/4" X 4 3/4"..... that way it can be closed off with two firebricks when not needed as a "pass through".

Once the "doors" were welded to the shell, then it was time to add in 8" extensions on each side to create a large oval.


Now it's "bite the bullet" time......shelling out the approx. $500 for Kast-O-Lite 3000F castable refractory, and the FOB to get it here. The best deal I could locate was $58.90 per 55lb. bag, and $150 FOB whether I they ship one bag....or an entire pallet........ I'm getting 6 bags, which should do the entire lining of the forge, and give me a left over bag for future needs.

Once the castable arrives, the first thing is to pour the floor, and let it cure for a week, then get the burner holder placement set, and the forms built for the inside. I'll get more pics at it goes along and continue on this thread.
Last edited:
Planned on ordering the refractory today..... but the gal I deal with is out of the office. Might be next week before the order is placed.....and who knows how long to freight it here. The plan for now is to pour the floor first, let that cure for a while, then get the burner holder placed correctly......then i MIGHT be ready to pour the liner. :)
Finally got started pouring the new welding forge today. I've never built one this its "learn as I go". :)

At first I wasn't going to put a steel floor in it...... but figured that since it's likely going to take a forklift to move this might be a good idea. I'd hate to see all that castable pop out the bottom a end up as a pile of rubble on the shop floor!

Mixing tube, castable, water, and all my homemade tools for mixing and getting the castable in place. I put a thin layer of castable in the bottom, then added 5 fire bricks as "filler" to save as much castable for the walls as possible. I spaced the bricks, filled the gaps, then put about a 1" layer over the top. Now its going to be about a week of cure time before I can locate and install the burner holder, then it will be building the interior forms, and then hopefully I can "fill er up" :)

More to come!




Last edited:
Lookin' good Ed!
Are you going to need to use forms for the walls or is the refractory thick enough to stick in place with thin layers?
Its gona need forms. The plan is to buy a length of 10" diameter "sona" tube (concrete form), split it down two sides to create two 1/2 circles. Those will be the radius at the front and back doors. I'll use 1/4" plywood for the sides. I'll use a heavy cardboard tube to form the burner hole, and a hole for the thermocouple.....that way if I can't get it all out when everything is will just burn out when I burn the forge. Once the castable cures out, it will get a slurry coat of ITC-100. I'm also gona nose around some local tile stores and see if I can find some ceramic tile to act as a catch pan in the bottom for flux.
Good idea with the cardboard form tubes. That's the part I was curious about.
If the flat sides get stuck, a piece of pine might be better to burn than ply?
I was yaking with a friend last night..... and am seriously considering putting a single layer of kawool along the shell. then filling the rest in with castable. Forges are always a choice between durability and insulating efficiency..... castable is more durable, but not the insulator that fiber blanket is....... just another "lesser of two evils" choice. :) the pics of the rest of the forge build processed and upload to photobucket.....

Had to weld the burner holder in place.....Used some sch 80 pipe, then drilled and tapped three 1/2-13 holes located approx. 120 degrees apart...



Next I built the forms. 10" diameter concrete from tube from Home Depot. 19" piece, split down each side. I used some 1/4" plywood ($5 for a 1/2 sheet at Home Depot), and cut 6" wide X 24" (just because it was that size) pieces to fill in the rest of the form.

I used duct tape to put the form together....hopefully that will make it easier to get the forms out once the castable cures enough...



I also picked up a 2", sch 40 PVC conduit, 90 degree. I had to heat and form it to get the radius I needed. But the idea was/is to form a channel in the castable that will "guide" the burner flame around the inside. After getting the dent I needed, I sawed the PVC with a taper around the curve that terminates about mid way on the opposite side of the forge that the burner enters.





I also used the 1/4" plywood to fill the front and back "doors", trying to ensure that castable would cover most of the steel portions of the doors.....again....used the duct tape to keep things in place.




Since I had a limited supply of castable, I decided to do a "hybrid" forge.....used 1" of #8 density kawool next the shell, and used the castable for everything inward from there....



5 bags of Mizzou 3000F castable later......




Now to leave it alone for about 2 weeks.....then try to take the forms out. After that I suspect it will be a month or so before it will be cured enough for some firings.
Last edited:
very nice. this is looking gooood, and the WIP is very informative. thanks, i'm looking forward to seeing how this finishes up.
Justin: The castable is about 2 1/2" thick, give or take a bit from spot to spot. I intentionally made the castable a bit thicker on the front, and the off burner side. Historically, these have always been the parts of a welding forge that fail/need repair first, so taking that into consideration, I tried to beef those areas up a bit. The one thing I totally forgot to mention in the WIP was putting a hole on the upper left side near the back.....for a thermocouple.
Dang Ed. That thing is going to be EPIC! Thanks for sharing the images and give such good explanation of the process so far. If I were a betting man. I would have to put my money on "Ed for the win"
After checking on the new forge this morning, I was pleasantly surprised to find that it appeared cured enough to remove the I did. It wasn't too tough of a job. I cut the tape with a razor knife, and pried the forms out of the "door" areas. Luckily, everything came out smoothly.


I suspected there would be some dressing up needed on the door openings, so I grabbed a ceramic tile file that's been in the shop for years.....


After a bit up filing with it, I got the front and rear opening cleaned up nicely........



I'm thinking that forming in a "flame channel" might have been a good thing. Guess I'll find out when it cures enough to put in place and fire. A little bit of the duct tape got hung up in the curing refractory, but my guess is that won't be any big should just burn out when I fire the forge for the first time.


Looks like my measurements worked out correctly for using fire brick in the front and back "doors"... here's a pic of the front door...from inside the forge....


I'm thinking that after it cures, I'll take the torch to the inside to burn away all the stuff left over by the forms...... gotta make sure the surfaces are fairly clean prior to coating the interior with ITC-100. :)

As it gets closer to completion, I'll take some pics of the burner assembly, and might even do some video.
Last edited:
Thats the idea. Another reason I like a vertical forge for welding is because the billet is suspended in the forge... rather then laying in a puddle of flux, as generally happens in a horizontal forge. I'm putting the forms together for a lid.... gona build it just reverse of the forge..... kawool to the inside, and the rest castable.