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Ground forge construction.


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Good evening guys,
I would welcome some advice on building a small ground forge, to burn blacksmiths coke nuts.
I have volunteered my services to give a knife blade forging demo to a small group of my friends.
The demo will take place in the local forest (away from trees).
There will be a small blower available if required. Basically I want to build a small ground forge as simple as possible-will have to remove it after use. I hear that there can be quite a lot of heat loss into the surrounding ground if not properly insulated. I have a number of white soft fire bricks that I could use for insulation if need be.
Any help on dimensions and sketches would be great. Unfortunately I will not have time to get the ground forge right on the day as Ill only have time for the blade manufacture . Any advice from those of you who have experience of building ground forges would be of great help. Also any of the pitfalls which I should look out for.
The demo is on the end of September so I have time to get all the raw materials together. Im sure all the guys Iknow are looking foward to this so any advice would be greatly appreciated.
Thanks Hammer and tongs

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The side blast as it is the simplest to construct. BP0238 Simple Side Blast 55 Forge.

If you construct the BP0238 forge, you may want to fill the forge with ash (or clay) then scoop out a depression for the fire (saves on the amount of coal being used). Play with the fire (shapes and sizes) till you get the feel for the forge and how it heats.

Then take it with you and lay it on the ground and pile a little dirt to cover and hide the sides, instant hole. It is the same forge you used at home so you know how it works.

Give the forge away at the end of the day to a deserving lad that showed interest in blacksmithing.

Oh yes, find a shade tree to put the forge under. A couple of hours in the hot sun and you will know why. (grin)

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I believe it was Sears who used to sell what they called a portable miners forge in a wood box that consisted of a small blower like a rivet forge with a set of folding metal legs on the back side and a cast iron tweer iron, It was used for dressing steels, (sharpening the cutting end and also working the mushroom), from the striking end of the drills that were used to drill holes for explosives. You simply dug a hole in a convenient bank stuck the tweer iron in the side of the whole and using charcoal from your campfire, you had an instant forge. A double jack (12lb sledge was usually used for an anvil with one face stuck down in the ground at a convenient location next to the forge.

Earth (dirt) is a good insulator.

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Hi hammer. If you want to build a ground forge on demand, you should have the parts ready. Then, you can build it fairly quickly. It took me a few hours to build mine, since I had to modify some parts.

You start with a hole in the ground. Dig this with a small hand trowel, then put a brick border around it. Red clay bricks are OK. Use a brick with a hole in it for the tuyere end, as it shows in the blueprints for the 55 side blast forge. Be careful if the ground has a lot of organic material. Fill in the bottom with ashes to keep fire from spreading. A piece of old 3/4" plumbing pipe can be used as a tuyere, but it will burn off after about 20 uses. Be careful about zinc fumes if the pipe is galvanized. You will have to get air into this pipe. I used a disposable camping propane cylinder with the neck and base cut off. The base makes a good parts tray. Do not use the other end unless you are very confident with your silver soldering skills (instead, buy the conversion fitting at a camping store). If the fit is poor, it can be fixed with a few wraps of crumpled aluminum foil. Into the bell end, blow with a small blower. A leaf blower will work. In fact, mine worked great until one brush wore out. Then, when I replaced the brush, the motor was too powerful, and blew too much. You can reduce the air flow by moving the nozzle of the blower away from the open end of the disposable cylinder. Fill the brick bordered depression with checks from defunct bank accounts, and junk credit card applications, light, sprinkle lump charcoal, and start blowing. This forge will handle large ornamental items that can be placed on the flat, and it will get hot enough to weld. It can be disassembled and reassembled in 10 or 15 minutes if the ground is not too hard. Douse fire by splashing water, then sealing the opening of the depression with a brick.

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i have made floor fires to weld heavy sections ,all you need is ,a blower, with a blast gate, a short stainless steel tube to make the tweer, steel flexi pipe to join to blower and molding sand to make the pit ,dig a hole and trench for tweer and flexypipe damp the foundry sand ,and ram it down hard ,set the tweer and ram the sand around it ,set the blower up ,throw in some embers and coal, start the fan ,and get your iron hot, 1 hr max,

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I've always just dug a hole in the ground stuck a tuyere down in it and forged!

Fancier ones for multiple days' use get built up of firesfe rocks and clay and wood ash---often a "corner" of a fire ring so I have a wood fire making me charcoal on the spot.

Insulation? does ground transfer more heat than a metal forge pot exposed to the air does?

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Glenn Thanks for the thumbnail and line with ash advice-makes sence to me Great idea to give the forge away at the end of the day-I kinda had a similar idea in mind if I could collect an old BBQ from the junk yard-this forging is contageous.....Thanks

Irnsrgn-Your portable miners forge sounds interesting-will follow up with some research. why did miners need such a piece of equipment -was it to repare shaft supports or for repair of mining tools and equipment, I wonder, will make for some interesting research.

Evfreek I agree parts should be ready (tried and tested before the demo-guess this will avoid the dreeded 'demo effect' which ive experience quite a few time in my life at work on doing exhibitions etc, if you follow my drift.
Great idea to control the air volume with the cone from the used pcamping cylinder-good consept-one of the guys voluntered a leaf blower -I could see the air being reduced nicely using your concept-Thanks

Bruce-Nice and simple I like-easy to source components from the Junk Yard hey we are talking the same language.Thanks

Thomas Keeping it simple-good advice which I shall use.
Many thanks for you time and interest guys ill keep you posted on any developments and pictures from the demo day-I cant wait Cheers H&tONGS

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Miners used forges to repoint their picks and hand drilling drillbits (used to drill holes for blasting charges)---a regular necessity in hard rock mining and almost any mine or quarry of appreciable size and age had a smithy associated with it.

I still hear tales of people running across blacksmithing tools at abandoned mine sites way in the back of nowhere here in NM---unfortunately they have never brought any back for me---yet!

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Heard or read about a guy who dug a trench in the ground layed a piece of pipe in it.with holes drilled in it then built up the sides with clay from the creek let it cure attached his blower or air source to it and then proceeded to forge don't if ti's true or not but sounds life it might work

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I still hear tales of people running across blacksmithing tools at abandoned mine sites way in the back of nowhere here in NM---unfortunately they have never brought any back for me---yet!


Yeah, those stories kill me. Seriously if they WERE friends, what's packing a couple anvils, forges and related tools out of the woods for you?

I mean really, what are friends for? ;)

Frosty
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Heard or read about a guy who dug a trench in the ground layed a piece of pipe in it.with holes drilled in it then built up the sides with clay from the creek let it cure attached his blower or air source to it and then proceeded to forge don't if ti's true or not but sounds life it might work


This is pretty much what's being discussed, Bruce.

Typically though the air blast is through a side draft rather than a bottom draft. (the pipe with holes under the fire) A bottom draft tends to eat up tueyere irons faster and a person packing their smithy on their back isn't likely to want to haul extras with them.

The air blast is another thing that is easy to produce without anything more special than a sack. If you slip a sack over the end of the tueyere iron you can open the sack, inflate it then clamp the open end down and squeeze the air out through the tueyere iron.

A sack can be hide, stomach or any number of woven fabrics (a tight flexible basket falling within my definition of fabric for this discussion) and can be used to carry more stuff when it's not being your bellows of course.

Using a sack bellows the smith doesn't need a lot of equipment. A stump anvil and bick, tongs, hammers, (If a smith were particularly limited for weight wooden handles could be made on site and not packed along) chisels, saw, files, tueyere iron and stock. I call it a tueyere "iron" but a thin walled copper/bronze tube with a clay nozzle will serve perfectly well. In fact a piece of rolled birch bark or large reed and clay nozzle will work fine.

Then there are any number of more advanced bellows like feather, box, single and double acting, etc.

The actual minimum equipment list for a blacksmith is really short. A hot fire, something heavy to beat against, something to beat with, something to beat on and if the beaten upon thing is too short, tongs to hold it.

A person doesn't really need much more and can make most of the rest including the iron.

Frosty
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I'd seriously consider using something other than coke. I'm not sure what kind of set up you are thinking of, but coke requires a pretty hefty blast and a sizeable bed to be usable. Much of the advice you have received, while good, doesn't take into account the fuel being used, which is entirely understandable as coke is not particularly common in the US.

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Hi Dan, If I dont use coke would what would you suggest I use in a ground forge. Thing is I havent any long term experience forging with charcoal although I understand that it can be used Is there any other fuel that I could use, dont want to over complicate things. Ive just got hold of some old blacksmiths bellows which are foot operated-hope to use these for the forging demo.(in which case I have the oportunity to use the forge tray which is above it.

Need to recondition the leather on the bellows -what should I use for this guys any suggestions greatfully recieved.
Regards H&Tongs.

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Hi. I finally got a chance to get some pictures of my ground forge construction. All the work is in the tuyere, so most photos are of that.

Start with a junk disposable propane cylinder such as those used for camping. Preferably, use one which is a little rusted out, so it contains only air. Chain drill holes around the neck. This is only a little slower than the blue ax, and it is a lot safer.

Use a cold chisel to chop the area between the holes to make an approximate 1" hole in the top. Discard the screw fitting.

Jam a 3/4" pipe nipple part way through the hole. Use crumpled aluminum foil if it is loose. Put the most rusted end at the business end. Less zinc fumes this way. This tuyere will generate fumes the first time you fire it up, but the amount is small, since only the first 1/2" will burn, and this is mostly corroded off anyway.

The open end of the cylinder is the air receiver. Blow air with a leaf blower or reversed vacuum cleaner into this. If the blast is too large, move the hose out of the receiver allowing air to leak around the sides.

Here is a shot of the bricks in the ground. The depth of the coal (charcoal) bed is the width of one red brick. Note that the kind of brick with holes in it was used for the tuyere side, just like the 55 forge blueprint.

This forge will work with coke if you use an electric blower. The clinkers will form under and slightly in front of the tuyere end. Hook them out with a curved poker after lowering the air blast.

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Hammerandtongs- I would recommend you use charcoal, which does take a bit of getting used to, or you could try coal. The problem with the latter is that the only readily available stuff is house coal in bags, which may not be suitable, and seeking the advice of many coal merchants is a bit of a waste of time, as they are mostly not experts on the matter of forgework(!). Having said that, I have used crummy smokeless house-coal to forge and even fireweld, so you never know. An excellent blacksmith's coal still available (I think) is Maltby Bingles from RJB.
I have never heard of a foot-operated blacksmith's bellows (not that I'm an expert), but if it's from one of those farriers forges, or one of those jewellers/apothecary bellows you will definitely have problems using coke.
I can't offer any advice on reconditioning leather, other than that I would carefully consider whether it is worth doing, as leather, unlike wood or metal, can't really be brought back to life once it is knackered, especially for the purpose of rigorous use as per a bellows. Better perhaps to replace it?

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This is probably a bit late for the event but I ran across a couple Youtube videos of ground forges.

The first is a middle video in this guy's knife making series. Please do NOT build fires like this guy! At least clear the leaves away first.

YouTube - Greenpete's Knife Making pt3of4

This one is a Laotian smith and is part 1/2 it's short but shows his forge. 2/2 shows his anvil and power hammer. :o

YouTube - Laotian blacksmiths part 1/2

Notice his smithy seems to be a family shop, grandpa feeding the forge out front and baby sitting in the rear.

Frosty

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