Aspiring blacksmith need advice on forge build

[MadsRC]

I'm recently gotten the courage to start blacksmithing. Ideally I'd like to start making small stuff like nails and hangers, eventually upping my game to tools, knives and axes. While I'm new to blacksmithing, I'm not totally new to metalworking, as I've worked lathes and routers ("manual" and CNC controlled ones) many years ago.

I've decided on a wooden framed forge. I've attached a picture of the frame I've build. It's about 5cm (Sorry for not using Imperial, I'm Scandinavian) higher than my ideal anvil height. I plan on casting a refractory in the large open area. For reference, I've attached a picture of the forge that inspired me

Now, the area that I'm gonna cast the refractory in is 80x80x20cm with a center opening for a tuyere. I wasn't sure on the tuyere size, so I made sure the hole is large. The thing that troubles me is that I'm not sure what recipe to use for the refractory, as I'd like to avoid setting the wood on fire.

Could somebody advice me on the useable recipe?

The other thing I'm not sure about yet is the size of the "firepit". What would be an optimal size for a forge of this size?

Regarding the blower, I haven't decided on hand-crank or bellow yet. I'm gonna read a bit more up on the subject and decide. The only thing I know is that it can't be electrically powered, as I'm building the smithy outside, quite some distance away from an electrical outlet.

 

EDIT: Corrected "correct" to "useable"

[ThomasPowers]

Location?  Or can I just suggest you source your refractory over there...

Here in the USA I would use a mix of clay and wood ashes and clean quartz sand; some would just use wood ashes---dampen them down slightly and pack them in; others would use dirt (though adding wood ashes to it gives it a bit more "flexibility".

Can you please give the parameters on "correct" rather than "usable"

[MadsRC]

I'm located in Scandinavia, more precisely Denmark.

I planned on using a mix of Portland cement, sand and fireclay (Which I've been told is also called Chamotte clay, which I know I can source over here). But I've come in doubt after a member told me that portland cement will, I think it was unbind?, it's water when it reaches above 500 degrees Fahrenheit.

Most of the firebricks I can find over here is rated to 1200C, which I think is a tad to low. I can get refractory mortar that can withstand 1600C, but it says that you should use it as mortar and not for molding (Said something about a max thickness of about 1CM)

[MadsRC]

Looking at Charles R. Stevens post, and re-reading your reply, I'll research using a mixture of clay, sand and ashes and see what happens.

[Charles R. Stevens]

I certainly would not use Portland cement, alumina based cements work but are over kill. 

My suggestion is to re work your box just a bit, your ansesters used side blast forges and charcoal, forging tools and weapons that they used to nearly "colonize" all of Northern Europe, and extended their trade to the med. honestly a side blast with a 2-2.5cm ID will make a a nice 6-8" fire ball. I would suggest notching the sides of your forge so that you can pas long bars threw the center of the fire ball. As suggested, local meneral soil and ash works well, your neighbors in Briton use cinder and ash from coal.      

[MadsRC]

Great advice Charles. Guess I'll close the hole in the bottom, and insert the tuyere from the side of the box. Just need to work out the depth of the firepit, so that I know where to place the notches and how deep. Any idea about the dimensions of the firepit? I'm looking for something in between the size your example and the example that inspired me.

 

I've got a large fireplace with lot's of wood ash, so I got that covered. Could also dig up some clay, but I found a place selling Red Clay with 20% chamotte for 20USD for 10KG... Might just buy a bag of that.

 

Any idea about the ratio of clay, vs ash, vs sand?

[Hexus]

I'm actually teaching a tool building course early next month at College of the Rockies (BC Canada). In that course we will be building a forge for each student. Coal forge with electric blower, brake drum as a fire pot. You can go without refractory (especially if the alumina refractory costs more than a small sheet of 16ga....or you don't have a welder and want to stick with wood box). I've done a wooden box forge as well (with a sheet of 16g on top, so just a frame with 2 rails mounted on the top of the wood, countersunk so the sheet is level with  wood deck) and it has been working for quite some time at the Heritage Park I used to work at (historical to circa 1890). The picture below just show the 2 inch piping and the clinker breaker I made from scrap.This particular setup I use for medieval shows with my bellows I crafted. All the piping is hidden in the wooden box and under the sheet metal.

[Charles R. Stevens]

Not to insult any one but brake drums are a PITA, in my opinion. Better off with a simple pan like a rivit forge and a bullet grate or fabricate a fire pot, but then again charcoal really isn't all that happy with a bottom blast. 

I place the bottom edge of the inside hole in the tuyere 3" (7.5cm?) off the bottom of the box, I like to drop a couple of hard bricks in the bottom to keep me from digging to far down when cleaning out and remodeling the fire bowl. The top of hole in the tuyere comes to 3-4" ( 7.5-12cm) of the top of the table. This leaves 1" (2.5cm) under the tuyere to collect slag. With charcoal a 6-8" across bowl is the answer, other wise you need more tuyeres other in a simi circle for a bigger fire ball or in a line for a trench (heating a blade to quench or a long scroll or a buggy spring) now if you use coal it will stick to clay something fierce.

Or atleast the clinker will. Some folks say ash will prevent this but I don't know. My suggestion would be something on the lines of 1 part clay, two parts sand and 1 part ash, line the box with 2" (5cm) all around (this will protect the wood) then you can fill in the front and back (behind the tuyere and infront to take up space, then fill the rest in with equal parts sand and ash. You simply dig out the bowl. This way you can dig it out and add a manifold to make a trench fire or a bigger fire ball ( for forging anvils...) of corse your ancestors used soap stone "bellows stones" and basalt and grannet where we use bricks and steel. 

[MadsRC]

The part about the 2" lining is awesome! Exactly the info I need. I was under the impression that the mixture would harden, but if I understand you correctly, it'll be more akin to play dough, allowing me to rework it? If that's the case, then it's even more awesome as it'll allow me to place more tuyere pipes if needed for larger projects.

 

Doing it as my 800th/900th AD ancestors would be my goal.

[Hexus]

Yeah the brake drums can be a bit fiddly as you have to fill in the holes and cut the clinker breaker hole (and the cast doesn't take to welding nicely). Other than that it isn't much of a bother. The idea behind them is there is less work than crafting an entire fire pot...and they're cheap. If one didn't like the bottom profile (because they have a 90deg edge at the bottom---which doesn't track shovels nicely) you could easily make a mini bowl to fit inside....at that point though you are already on your way to forging a new firepot). It is more a matter of supply cost/time/inventory on hand/acquisition of inventory.

[Charles R. Stevens]

6" to 2" bell reducers with a simple 1/2" "S" for a grate works well and as one can only effectively forge about 6" at a time it works very well, but so will a 4" deap steel tub, or drain pan, bolt on your tuyere, drop in a 2" cap with a 3/4" hole in the middle, fill with sand or ash and cinders and sculpted a fire bowl. Even cheaper if you have your local exaust shop sculpt the tuyere for you from exaust tubing.

but a 7 1/2" box, tub, cut off drum or flower pot with a 3/4" peice of schedual 20 pipe is cheap, easy and fast. Salvaged pallet, and you have material for a box, 12" nippel, a "T" a valve and blower of choice, walla. 3/4" is a lot cheeper than 2"! If you don't have a hacksaw, the. Buy a 2" nipple and a 10" one. 

Lots of folks start with a brake drum (so did I) but their are easer to build and manage forges, re think your forge design for your class and save your students and yourself time, money and agrivation. Besides, charcoal dosnt much like bottom blast forges, 

[MadsRC]

6 minutes ago, Charles R. Stevens said:

6" to 2" bell reducers with a simple 1/2" "S" for a grate works well and as one can only effectively forge about 6" at a time it works very well, but so will a 4" deap steel tub, or drain pan, bolt on your tuyere, drop in a 2" cap with a 3/4" hole in the middle, fill with sand or ash and cinders and sculpted a fire bowl. Even cheaper if you have your local exaust shop sculpt the tuyere for you from exaust tubing.

but a 7 1/2" box, tub, cut off drum or flower pot with a 3/4" peice of schedual 20 pipe is cheap, easy and fast. Salvaged pallet, and you have material for a box, 12" nippel, a "T" a valve and blower of choice, walla. 3/4" is a lot cheeper than 2"! If you don't have a hacksaw, the. Buy a 2" nipple and a 10" one. 

Would you be able to share a picture of the tuyure? I'm having a hard time figuring out what the T part is for. The valve, I guess, is for regulating the airflow?

How about the end of the pipe, put a grate (?) or something else on to prevent clinker from entering the pipe?

[Charles R. Stevens]

I use the "T" and the valve as a waste gate, as the small electric bed inflator I use for this set up is noisy when restricted (but it uses a separate fan for cooling) in my old age I don't care for the noise (to much like a vacuum cleaner). The first set up just used the valve in line. 

The clay, sand ash mix will harden, and will vitrify if you make the bowl out of it, that's ok for charcoal but if you ever use coal the clinker will stick. To make it so you can remold it, you want to leave a trench, then omit the clay from the fill. Then you have a "hard liner" wich keeps you from digging to close to the wood when "remodeling" (you can do the same with bricks) and then a sand box. I do use clay to support the tuyere, and have experimented with screwing a floor flange on the end. The clinker dosnt stick to the steel flange, and I can mold clay right up behind it. 

[MadsRC]

Thanks mate, really useful info.

How about the clay, will any kind of clay work, should I get solid or granulate?

I think the above is my last question, and I'll have enough info to hopefully start this weekend!

[Charles R. Stevens]

Basically the back of the box is filled with the clay mix (we call it Adobe, similar to the daub and cob mixes from Europe) up to about 3" (7.5cm) from the center line, with the tuyere imbedded. This putts the fire in the middle of the table. Now you want to make the trench wide enugh to hold a manifold, so go atleast 6" (18cm) from the center line. Or just make it all the way to the front (assuming a box not much bigger than 2/3m or 2') a classic size is 32" square (95cm). 

Keep a few bricks around as "furniture" to help in holding stock and remodeling your fire. 

Any clay you find will work, can't find clay and have brick? All good, no brick but soap stone? Points for cool, granit cobles, hijacked an old flower pot 60cm across? Old was tub? Cut off from a 200l drum? All good. Note on clay, the drier the better, the consistency of modeling clay is good, drive it in with a mallet. Think rammed earth, or pith. 

If you rather mud pies, then mic in straw, horse or cow dung. The later makes a kind of "paper mache" 

[Hexus]

5 hours ago, Charles R. Stevens said:

Lots of folks start with a brake drum (so did I) but their are easer to build and manage forges, re think your forge design for your class and save your students and yourself time, money and agrivation. Besides, charcoal dosnt much like bottom blast forges, 

I've used a brake drum for 10 years, no heartache here. The main issue is people often get drums that are too deep, causing too much fuel to be used to get your heat to build upwards through that much depth of fuel. I've also used a 500$ firepot from Centaur Forge and 400$ setup from the blacksmith depot. I like a solid bowl (not refractory, unless i'm setting up a propane forge, but ive also used kaowool for mini forges), something that is not really much fuss cause I can modify it quickly with grinder cutting disks and a simple welder with scrap on hand. I use coal extensively...sometimes propane when I do production work.

 

I've never like a screen opening on the bottom....I want to have a clinker breaker in there to deal with crumbly bits of clinker. So it is rather easy to cut a rectangle in the bottom of the brake drum to facilitate that.

 

[Charles R. Stevens]

i get that, but you still have 2" pipe fittings and an ash dump, plush attaching it to the drum and holding it in a table.  In a ducks nest or pan type forge a "bullet grate" or simply a 2" pipe cap with a 3/4" hole drilled in the middle allowes the slag to roll of and form a pool below the air inlet (what a side blast dose) and it usualy comes out in a ring, like a cruddy glass donut. Simpler than a drum. 

Side blast on the other hand typicaly use smaller tuyeres, and their for are cheaper and easer from the get go, then they are simply filled with ash and sand. The air comes in from the side, and the clinker flowes down below the tuyere. 

I'm saying that brake drum forges suck all the way around, heck I think Thomas Powers still has one in his shop, many smiths do and they like them, but they are a bit harder, and often more expensive to build. 

The only reason for "Adobe refractory" or bricks is to keep me from getting to rambunctious and digging so far down when I'm remodeling and cleaning out the fire that I expose the wooden floor. 

Now, that all said, a steel or cast fire pot in a steel table is more portable than a box full of dirt. In that case, a budy has a real nice set up that uses a 6 to 2" bell reducer and 2" fittings, the grate/breaker is a peice of 1/2" square forged into a "S" that sets in the bottom, works great, no isues with clinker sticking, portable and makes a nice fire ball that will beat a chunk of steel up to welding temp about 6" long. 

Myself, I like my side blast and a shovel for portability. 

 

[MadsRC]

Moved the box to my designated smithy area today. Right next to a big pile of ashes and next to a pile of sand.

Unfortunately I found that the soil was too sandy, so I wasn't able to dig up some proper clay.

I ended up smashing up some red bricks and using that as the bottom layer. On top of that I put a thick mix of ash/sand and I dug a fire pit. I'm gonna bring home some coal tomorrow and do a burn-in. If it's successful, I'll only need to put in a side blast tuyure!

[Charles R. Stevens]

I would have just used the brick whole, lol. It's heat resistant enugh and you can't dig threw them. Live and learn, lol

Sand and ash will work just fine. 

[rockstar.esq]

If you have a welder it's cheaper to make a water cooled side blast with a remote bosh than it is to buy a new bottom blast fire pot.  I spent $50 all in, compared to $80 plus shipping for the smallest/ cheapest new iron firepot I could find. 

The clinker flows below the fire and congeals out of the way so you can keep getting welding heats without having to stop and clear the air blast.  I find it's easier to get a good  neutral fire with the side blast than a brake drum forge. 

I'm using sand and ash as my "bed" which means I can re-shape the fire any time.  The flip side is that you can't use bottom blast fire management methods like scraping the poker along the pot towards the grate because you'd just shove the sand around.  My second time using it, I accidentally shoved my ducks nest so hard that it wouldn't hold a barn swallow when I thought I was just consolidating the fuel at the bottom of the fire.

I don't really see an advantage to casting the bed in place.  As Charles pointed out, it's awful nice to be able to shovel the weight out of it whenever you need to move it.

I plan to set mine up with a sand "drain" to let me put a steel storage bucket under the spout and let gravity empty the works for me.

The remote bosh is an extra hassle to haul out, and it takes a good bit of water to keep from boiling.  My 15 gal bosh was steaming hot after five hours of forging last weekend.  Everything involved takes a bit longer to get set up, and to put back.  The sand bottom slows the cooling as well so it's still pretty hot up to an hour after the fire is out.  

That being said, I'm running coke which makes everything hotter than if you were running coal.

I guess it's worth mentioning that a sand bed plus a water bosh adds up to a fairly hefty weight.  The water alone clocks in around 125lbs and it's got to be higher than the tuyere for the water to circulate properly.  I figure I've got roughly 100 lbs of sand and ash in my tub.  That's a lot more than a little rivet forge would weigh which explains why bottom blasts are more popular with smiths who move their forge a lot.

[JHCC]

For those who didn't see Charles R. Stevens' "Just a box of dirt, or a simple side blast forge" thread, you can check it out here

[Charles R. Stevens]

Just remember I used clay because it was under my feet and I was using charcoal. Coal like clay way to much (clinker sticks to it like glue) sand, silt, fly ash ect all work well

[Hexus]

Ahh ok I got ya now Charles! More about the clinker gathering and blocking the port at the bottom. I hear you on that one. I have definitely found performance issues in the type of coal I use (50$/50lb bag).

From the UK the coal was a good heat, and the clinker formed into very hard nodules.

 The coal from Pennsylvania has an awesome heat, but the clinker is really crumbly and doesn't stick together that good. About a medium price (34$/50lb bag).

The coal I use locally (Elk Valley, Tech Coal, Kootenays), doesn't facilitate 50lb bags, need 1 ton min order, for 150$ (transportation gas inclyded). The heat is not as hot as the other two on average, but the clinker really likes to clump and stick together...so you can usually haul it out in one lump.

[Charles R. Stevens]

Yes sir, part of my point, and my like for bullet grates in bottom blast forges. In a ash and cinder filled side blast your two funky clinker isues arnt much of an issue, as when you clean out and sagar at lunch they just become part of the bed, lol. The brake drum forge has been an old stand buy sense the model T, but the side blast is still simpler and less expensive. Sherman's troups used packing cases and log cribs. 

[Frosty]

One reason your clinker is crumble instead of forming a more consolidated mass is you aren't getting the fire hot enough to fuse it all. Once you get the hang of how to get the fire working the clinker will start sticking together.

Just don't paint yourself into the new guy corner of adjusting for the wrong indicators. You want a HOT fire, not sticky clinker.

Frosty The Lucky.