Before we begin, I realized a possible problem with the information given in the prior lesson. That error is the size of the forge bed I specified. I designed this forge for my use, and realized I tend to use a much larger forge deck than most hobbyist smiths may have room or need for. Also, this amount of clay makes the forge bed quite heavy.
Here is a rethought size for the colonial forge, however it does not use standard sized pieces, so some ability to cut lumber will be required to construct this version.
The total materials list for this smaller forge would include these parts:
2 side pieces of 2x6 18” long (3 feet total)
2 rails of 2x6 24” long (4 feet total)
3 support rails under the forge of 2x4 20” long (5 feet total)
4 legs of 2x4 (or 2x6) 30” to 32” long
4 angle braces
And here is a cutting diagram to utilize the material fairly efficiently:
Keep in mind that this version will use a lot less material, weight a great deal less and take up less space in the garage than the prior version, and if these are considerations for you, you may be better served by this smaller forge. The construction methods and process is the same with either version.
Now with that out of the way, let's get back to the tasks at hand.
The air inlet pipe will be put into place before the clay bed is put in, and there are two options here. The first is to drill a hole through the end rail for the pipe to pass through. The second is to pass the air inlet over the top of the rail and hold it in place with a pair of nails or a wooden mount made from scrap.
To drill the large hole that will be required to pass the inlet pipe through the sidewall you will need a power drill and a hole-saw large enough to allow your pipe to fit, or alternately a series of overlapping smaller holes to make a hole large enough. I leave this option to you to sort out, as the plans here are designed for the pass over design. Of course, this step could also be done before the entire box is assembled, making the process of drilling the hole or holes a great deal simpler.
The pass over style inlet is designed for simpler construction, and uses a few scraps of wood to brace the inlet pipe for best results. This also sets the outlet at a slight angle which is something to be aware of once you start laying in the clay. Any scraps of wood you may have left over from the box construction can be used to brace the pipe, and I would suggest you put a thinner strip of material over the top of the inlet pipe for additional strength and stability.
A couple of heavy nails driven into the bottom of the forge bed hold the pipe in place before the clay is put in, and you will want to hammer them over the pipe so the heads do not stick up out of the clay after the forge bed is complete.
Mix up your clay with a small bit of water to make it easier to shape, and lay it in in layers, letting each layer dry a few days. This will help to allow trapped water to escape and reduce cracking that happens in a thicker layer of clay. I generally lay each layer about 1 to 1 1/2” thick. The first layer will help to hold the inlet pipe in place, with each successive layer making it even more stable. Build up a bowl around the mouth of the inlet pipe, much like the bucket forge, and refer to the illustration here for assistance.
You will need to let this clay bed dry for about a week before it can be used, though I do know of cases of these forges being built and used the same day in historical records. I am fairly sure the pressing need at the time outweighed any cracking that the heat may have caused in the clay layer.
Once the bed is dry, you will be able to start a small fire in the forge bed to drive even more moisture out of the clay. For this, a quarter bag of common BBQ charcoal works quite well, but a pile of dry sticks from the lawn will do just as well. There is no need to drive air into this first fire, you are simply drying the forge at this time. Allow it to cool and “rest” overnight before it will be ready for everyday use, as this gives the moisture in the clay time to migrate and even out throughout the clay bed.
In our next installment, I will detail building a set of bellows to get some air into your forge, and discuss possible alternatives.
Showing posts with label forge. Show all posts
Showing posts with label forge. Show all posts
20 September 2009
03 September 2009
Blacksmith lessons – building the colonial wooden forge
(images coming soon)
After covering the information in “building the bucket forge” you should have a pretty good feel for where this lesson is going. This is a larger version, and in place of the bucket we are going to build a wooden table with a box on it's top to contain our clay firepot. As this forge is more prone to cracking in the clay layer, I will cover repairs in more depth here as well.
These forges go back quite a ways historically, but most people seem to be familiar with them in a historical context during the colonial era of the United States, so we tend to refer to them as colonial forges for simplicity. You can also call them wooden box forges or what ever you like.
This forge is another variation on a ground forge, but puts the hole in the ground up at a comfortable waist height and with the addition of wheels on the legs of the forge, you can move the hole around for storage. That is much harder to go with a proper ground forge.
This forge can be built of any wood, even old pallets or the like. For the longest lasting version of this, I would suggest using 2x treated lumber. Just remember that anything that is used to make treated lumber isn't safe to eat, and shouldn't be inhaled. I leave it up to the person doing the project to be safe and take the required precautions. We are not going to cover a lot of woodworking safety here, so if you do not know how to run a table saw or what ever tool you are using FIND SOMEONE TO TEACH YOU how to do so safely. Seven finger Larry is not the guy here, OK?
I have provided a basic set of drawings with this post to guide you, but you may easily alter the dimensions of the forge to suit your need and materials. This version was designed for the most strength with the fewest cuts, just in case you are building it with a hand saw and no power tools at all. It also happens to use mostly off the shelf sizes of pieces, so you can probably find these boards pre-cut at your local lumber lot.
I tend to build these forges upside down, and add the legs last. This allows the body of the box to act as a brace as you mount the legs, making assembly a fair bit easier. So the first part to build is the box, which is quite simple. It is a box made from 2 foot long and 4 foot long sections of 2x6 (which are actually 1 1/2” x 5 1/2”). You really only need a single height of 2x6, though I have built these forges deeper using a second tier of 2x6s. The problem with deeper forges is the weight, while the problem with the single tier forge is the bowl is rather shallow. You can mound up the area around the bowl when you lay the clay in to compensate for this though. The box needs to be very sturdy, so feel free to go nuts with screws here on assembly... A screw every 4 inches is not at all excessive, and I strongly suggest heavy 3” long deck screws for this project. A big 5 pound box should not exceed 20 dollars even in the the most expensive store. If you are careful, large sinker nails can be used; I simply prefer screws, as they tend to hold tighter and stay in place longer.
I generally use a secondary strip of material inside each corner, and screw into that as well, driving the screws from the outside. A section of 2x4 or 2x2 cut to 5 1/2” long is quite nice, though be careful when you drive the screws into the wood from the outside; quite often the sharp tip of the screw will be exposed on the inside of the box, but this will not be a problem once the clay liner is put into place.
Once the main box is framed in, screw the bottom boards into place. The bottom is actually 27 inches across, as the end boards are 24” long and the sides are each 1 1/2” thick. Here you can continue to use 2x6 material, but it will require more pieces than if you use wider boards and will not line up exactly. 3 sections of 2x8 and one section of 2x4 could be used for example, and would not require you to cut a board lengthwise (this is known as “ripping a board”). You could even use a number of 2x4 sections. No matter what you choose to use, just be sure the boards are well secured at each end and are free of any cracks going across the board, as these will be supporting a fair bit of weight once the clay is in place. Get these boards as close together as you are able, so you do not have to worry about your clay draining out (though you can line the forge bed with plastic first just to be certain). Once these lengthwise boards are in place, three or four crosswise boards need to be screwed on underneath. I generally put one at each end, inset a few inches so I don't accidentally hit the screws that hold the long boards on when driving the next set of screws, and two more evenly spaced across the length. The illustrations will probably make this more clear. These cross ribs are screwed into each board in multiple places to help spread the weight of the clay bed once the forge is finished.
At this point, turn your forge bed over, and if you like, you can add reinforcing pieces to the corners. This can help to hold your forge together but does add more weight and uses more material.
Now the legs need to be cut, and these are not usually a normal length that you find precut at the woodlot. I usually make my forges about 32 inches high, but you can vary that somewhat. The goal here is to make the forge height roughly the same as your anvil height and that will vary from person to person. The easiest way to find out what this height should be is to have a friend help take a measurement from your knuckles to the ground, with your arm hanging straight down at your side and your hand rolled into a fist. By setting your forge and anvil at the same height, you allow yourself the ability to lay long rods of steel across the anvil and into the forge to heat the ends without having them fall over and possibly burn you or cause damage. It is not critical that your forge is the exact height though, so do not trouble yourself in trying to get it exact.
I generally use 2x4's to build the legs. They are more than strong enough, and 2x3's would probably work, but I like the extra material to hold the screws safely in the wood. Having a leg suddenly pop off when your forge is at nearly 2,000 degrees is excitement you simply do not need in your life. 2x6's are also certainly a possibility, giving even more material to hold the screws, but do cost more than 2x4's.
I strongly suggest some angle braces and cross braces, as shown in the illustrations, but they are not mandatory. Also, I generally drill a set of holes in each leg and the side of the forge box, and use ¼-20 3 1/2” long threaded carriage bolts at the center of the screw pattern for additional strength. The nut goes on the inside over a large “fender” washer. This washer spreads the force holding everything together over a larger area so it is less likely to crack the wood. Now the woodworking part of the colonial forge is complete, and in our next installment we will lay the clay firebowl and bed, and get everything ready to go. In later installments I will cover building a set of bellows that is fitting for a forge of this type as well.
Until then, stay out of trouble.
As a side note, I am sure I will realize I missed something and have to edit this over time to fill in those missed bits, so it may be wise to come back from time to time and reread old posts to see if new details have been added. I probably will not be rerecording the audio versions, unless it was something really major that was overlooked.
After covering the information in “building the bucket forge” you should have a pretty good feel for where this lesson is going. This is a larger version, and in place of the bucket we are going to build a wooden table with a box on it's top to contain our clay firepot. As this forge is more prone to cracking in the clay layer, I will cover repairs in more depth here as well.
These forges go back quite a ways historically, but most people seem to be familiar with them in a historical context during the colonial era of the United States, so we tend to refer to them as colonial forges for simplicity. You can also call them wooden box forges or what ever you like.
This forge is another variation on a ground forge, but puts the hole in the ground up at a comfortable waist height and with the addition of wheels on the legs of the forge, you can move the hole around for storage. That is much harder to go with a proper ground forge.
This forge can be built of any wood, even old pallets or the like. For the longest lasting version of this, I would suggest using 2x treated lumber. Just remember that anything that is used to make treated lumber isn't safe to eat, and shouldn't be inhaled. I leave it up to the person doing the project to be safe and take the required precautions. We are not going to cover a lot of woodworking safety here, so if you do not know how to run a table saw or what ever tool you are using FIND SOMEONE TO TEACH YOU how to do so safely. Seven finger Larry is not the guy here, OK?
I have provided a basic set of drawings with this post to guide you, but you may easily alter the dimensions of the forge to suit your need and materials. This version was designed for the most strength with the fewest cuts, just in case you are building it with a hand saw and no power tools at all. It also happens to use mostly off the shelf sizes of pieces, so you can probably find these boards pre-cut at your local lumber lot.
I tend to build these forges upside down, and add the legs last. This allows the body of the box to act as a brace as you mount the legs, making assembly a fair bit easier. So the first part to build is the box, which is quite simple. It is a box made from 2 foot long and 4 foot long sections of 2x6 (which are actually 1 1/2” x 5 1/2”). You really only need a single height of 2x6, though I have built these forges deeper using a second tier of 2x6s. The problem with deeper forges is the weight, while the problem with the single tier forge is the bowl is rather shallow. You can mound up the area around the bowl when you lay the clay in to compensate for this though. The box needs to be very sturdy, so feel free to go nuts with screws here on assembly... A screw every 4 inches is not at all excessive, and I strongly suggest heavy 3” long deck screws for this project. A big 5 pound box should not exceed 20 dollars even in the the most expensive store. If you are careful, large sinker nails can be used; I simply prefer screws, as they tend to hold tighter and stay in place longer.
I generally use a secondary strip of material inside each corner, and screw into that as well, driving the screws from the outside. A section of 2x4 or 2x2 cut to 5 1/2” long is quite nice, though be careful when you drive the screws into the wood from the outside; quite often the sharp tip of the screw will be exposed on the inside of the box, but this will not be a problem once the clay liner is put into place.
Once the main box is framed in, screw the bottom boards into place. The bottom is actually 27 inches across, as the end boards are 24” long and the sides are each 1 1/2” thick. Here you can continue to use 2x6 material, but it will require more pieces than if you use wider boards and will not line up exactly. 3 sections of 2x8 and one section of 2x4 could be used for example, and would not require you to cut a board lengthwise (this is known as “ripping a board”). You could even use a number of 2x4 sections. No matter what you choose to use, just be sure the boards are well secured at each end and are free of any cracks going across the board, as these will be supporting a fair bit of weight once the clay is in place. Get these boards as close together as you are able, so you do not have to worry about your clay draining out (though you can line the forge bed with plastic first just to be certain). Once these lengthwise boards are in place, three or four crosswise boards need to be screwed on underneath. I generally put one at each end, inset a few inches so I don't accidentally hit the screws that hold the long boards on when driving the next set of screws, and two more evenly spaced across the length. The illustrations will probably make this more clear. These cross ribs are screwed into each board in multiple places to help spread the weight of the clay bed once the forge is finished.
At this point, turn your forge bed over, and if you like, you can add reinforcing pieces to the corners. This can help to hold your forge together but does add more weight and uses more material.
Now the legs need to be cut, and these are not usually a normal length that you find precut at the woodlot. I usually make my forges about 32 inches high, but you can vary that somewhat. The goal here is to make the forge height roughly the same as your anvil height and that will vary from person to person. The easiest way to find out what this height should be is to have a friend help take a measurement from your knuckles to the ground, with your arm hanging straight down at your side and your hand rolled into a fist. By setting your forge and anvil at the same height, you allow yourself the ability to lay long rods of steel across the anvil and into the forge to heat the ends without having them fall over and possibly burn you or cause damage. It is not critical that your forge is the exact height though, so do not trouble yourself in trying to get it exact.
I generally use 2x4's to build the legs. They are more than strong enough, and 2x3's would probably work, but I like the extra material to hold the screws safely in the wood. Having a leg suddenly pop off when your forge is at nearly 2,000 degrees is excitement you simply do not need in your life. 2x6's are also certainly a possibility, giving even more material to hold the screws, but do cost more than 2x4's.
I strongly suggest some angle braces and cross braces, as shown in the illustrations, but they are not mandatory. Also, I generally drill a set of holes in each leg and the side of the forge box, and use ¼-20 3 1/2” long threaded carriage bolts at the center of the screw pattern for additional strength. The nut goes on the inside over a large “fender” washer. This washer spreads the force holding everything together over a larger area so it is less likely to crack the wood. Now the woodworking part of the colonial forge is complete, and in our next installment we will lay the clay firebowl and bed, and get everything ready to go. In later installments I will cover building a set of bellows that is fitting for a forge of this type as well.
Until then, stay out of trouble.
As a side note, I am sure I will realize I missed something and have to edit this over time to fill in those missed bits, so it may be wise to come back from time to time and reread old posts to see if new details have been added. I probably will not be rerecording the audio versions, unless it was something really major that was overlooked.
28 August 2009
Basic blacksmithing – building the bucket forge
(Click on the image for a larger view)
Ok, we talked about this very primitive forge in previous posts, and here is the “how to” article to build your own bucket forge. Just so this is very clear, this is not going to be a really incredible forge, and it probably won't be very pretty, but it is simple and dirt cheap (that's a joke son, a joke... it will become apparent in a bit).
This bucket forge has not been covered anywhere else on the internet that I am aware of, but a lot of parallel evolution happens, so it is quite possible. You could think of this as a portable ground forge if you like, so any photos or information you might happen across on a ground forge could apply to this project.
So lets jump right into this then.
First you are going to need a bucket. A metal bucket or pail is certainly fireproof, but because of the way we are building this, any 3 to 5 gallon plastic bucket will work just fine.
Next, you will need some way of getting air into the fire. Here, I really suggest you use a section of steel pipe. Plastic pipe, such as PVC, is definitely going to melt and it won't last longer than it takes to get a good fire going. Copper pipe is going to carry a lot of heat back out of the fire, and could melt the side of your bucket, plus it is pretty expensive. Now for this project, any old hunk of 1 1/2” or larger pipe should suffice, though I wouldn't suggest much beyond about 3 inches in diameter. If it has an elbow or T connector on one end, that's even better. You will need a way to put a hole in the side of your bucket for the pipe to enter, but we will get to that in a bit.
Lastly, you are going to need some fireproof material to fill your bucket and make your bowl. This is where the “dirt cheap” joke comes in. Simple dirt can work just fine, with a layer of clay to make the bowl. And if clay is hard to come by in your area, kitty litter shouldn't be, and it is just pelleted clay. If you opt to go the kitty litter route, make sure it is the non-scented stuff, those scents could emit nasty fumes once they heat up.
Now that we have our materials, we just have to put it all together. The first thing is going to be a hole in the side of the bucket to allow the air pipe to come in under the fire. If your air pipe is just a straight section, it can come in higher up than if it has a T or elbow on it. The proper way to do this is to use a hole saw to cut a properly sized hole in the side of the bucket for the pipe to have a nice close fit. But hole saws are fairly costly, and this thing is to be done on the cheap, so... you will need to heat the section of pipe at one end, and find a means of safely holding the pipe to melt a hole in the side of the bucket. For this a propane torch can work, or a small camp fire. You only need to get the end of the pipe up to about 400 degrees, so even putting it in your grille or oven would work. Now wrapping a wet towel around the pipe might seem like a safe way to hold it, but go with me on this... it's not. If the pipe is long enough, you should be able to hold in with your hands, as long as you check it with the back of your hand first. By that I mean hold the back of your hand near the potentially hot pipe and feel for heat. Then get a bit closer and so on until you can touch it and know for certain it is a comfortable temperature. Why use the back of your hand, you may ask? Because the back of the hand is more sensitive to heat than the palm and fingertips, plus if you do burn yourself, it is in a place that wont cripple your ability to keep working. If the pipe is too short, or the heat moving though it has heated it up, you will need something like a pair of pliers or vice grips to hold the pipe. DO NOT put one end of the pipe in a bucket of water. This can cause the water in the pipe to turn to steam and shoot out the end like a shotgun, and steam is very effective at causing burns.
Once you get your pipe heated up, you simply hold it against the bucket and let it melt the plastic. Be sure to do this outside on a windy day, those fumes can not be good for you. Also be sure there is nothing flammable nearby, like a wooden deck or a bucket of gasoline soaked rags. If the plastic flares up and starts to burn pull the pipe off it and let the pipe cool somewhat, and put the flame out either with water or a hand full of sand. Don't blow on it to put it out though, as that could easily splash molten, burning plastic back into your face.
The objective here is to get a hole that is just about the size of your pipe, about halfway down the bucket. Of course if you have a hole saw, you can use that too, but this is the low dough way.
Now that you have a hole, let the bucket and pipe cool back to air temperature. Next fill the bottom of the bucket with whatever is handy to make up the space up to the level your pipe comes in at. Dirt is just fine, but is rather heavy. Since this area will not be exposed to much heat, it can be filled with wood scraps, a couple empty cool whip containers with lids or what have you. Just fill any air gaps with dirt and make sure you have a few inches of dirt under your pipe for insulation. If you choose to fill the entire bucket with dirt, the forge will be much more stable in use, which is safer, just be careful moving it, as the handles on many of these buckets are not designed for that much weight. Now slide your pipe in through the hole you made so the open part is at the center. If your pipe has and elbow or T, you will have to put the pipe in from the opening at the top of the bucket, on an angle and slide it into position. Now fill the bucket with some more dirt around the outer edge to create a basic bowl shape. Tamp this all down from time to time to make sure the dirt is packed as tightly as you can, so it wont collapse later.
Next comes the final part, making the bowl. If you have river clay, simply press it into place forming a nice bowl shaped depression with the sides packed tightly all the way to the top. If you are using cat litter, you will need to mix a little water into it so it is sticky, and pack it into place. There are illustrations on my blog to better show the shape and layout of this step, and that can be found at http://ironangelforge.blogspot.com/, along with other lessons.
Now you must have some patience, and let the clay dry for several days. Once you have let it dry, check it for cracks, and if some have formed, mix up a little clay and water and patch the up nicely, and let it all dry again. If you have no cracks, congratulations! You just built a bucket forge! You may want to build a small fire of paper and sticks in it to bake the forge bowl, but don't get to gung ho, you are just trying to drive out more of the wetness in the clay, not build a fire that can be seen from space.
Lastly, you will need to find a few nice rocks to put in your pipe to keep the coal from falling down into the pipe. These are easy to come by along side gravel roads and some driveways. Try to steer clear of any rocks that have been in creeks or rivers, they could still contain water and explode or turn to powder under heat. We will cover how to use those rocks in our next installment, which will also cover putting air into your bucket forge.
That's all for now, stay out of trouble til next time.
Blacksmith basics - the forge
Blacksmith basics – the forge
This post will cover more specific details on the forge a blacksmith uses in their craft than our previous post “absolute basics” did. This resource will cover mostly coal forges, with gas forges covered in a later article. I will be leaving out the exotic and semi-exotic heating sources here, such as electric resistance heating systems and solar forges. These other systems are more specialized in their application and generally financially out of the reach for the average hobbyist smith. In later articles we will cover some simple variations of the modern and historical forges that can be built very inexpensively and in short order.
The forge is a place that the smith can contain and control a fire to heat metal up to working range, which is usually hotter than a normal camp fire. The term also often means the building the forge is located inside of, and the term “forging” is something made in a forge. Forgery is not the correct term for making something in a forge though... that would be smithing, which comes from smite; to strike something. You know... blacksmith, a smith who strikes iron, which comes from the ground and fire black, as opposed to gold or silver.
The history of metal smithing is a long and varied one, and forges have undergone many variations and changes over the passage of time. Originally, the forge was a simple hole dug into the ground, and a blowpipe was used to increase the heat of the fire. As time passed, the smiths decided that standing up was a lot more comfortable than crouching down to work in a ground forge, but a few clever smiths dug holes to stand in next to their ground forges, and in a few parts of the world these ground forges are still used today.
The next evolution was to make the forge a roughly waist high table, either of laid stone or brick. This allowed the air-blast to come into the forge from under the fire, instead of from the side or above, which increased efficiency and allowed the smith to get even greater temperatures from his fuel. There are variations during this long age, including forge tables built of wood and covered in clay, side blast forges and long trough forges. For simplicity sake, we will only cover the generic, basic forge here for now though and save the unusual ones for later.
In modern times, the forge is often built as a steel table with a heavy walled cast iron firebowl or firepot at the center of the table to contain the fire. This forge bowl is usually several inches deep and a bit more than a handspan across. This allows a decent amount of fuel to be used, yet is not wasteful. It also allows the solid sides to absorb and reflect some of the infrared heat back into the center of the fire, increasing efficiency.
In all ages, the area around the forge bowl is often used to hold extra fuel and lay out work pieces and tools. Careful fire management will keep the fire contained in the smaller, central pot so as to not waste fuel. Many smiths build special fittings into the table to aid their work. These can be tool racks, special dies for forming or bending, or workpiece supports for long rods of steel.
So why build a large, heavy table for a forge in this day and age? Forges are an efficient means of heating steel compared to other options, such as a simple torch with either a fuel air mix or a fuel-oxidizer mix. The fuel air torches are things like a propane plumbers torch which have only a single gas cylinder. A fuel-oxidizer system like a oxy-acetylene cutting torch, will have a pair of tanks. The problem with using either style of torch is the amount of lost heat that is simply blown into the room and not absorbed by the work piece. The amount of fuel used by either of these torches in medium to heavy blacksmith work will make them prohibitively expensive in short order.
That about covers the basics of the forge, now we need to look at the fuel, air input assembly and the hood or draft system to remove smoke and heat.
Historically, forges burned coal, charcoal or in some rare cases peat moss as fuel. Raw wood is generally not clean burning enough to be used as is, so it was usually rendered down into charcoal, which gave a better heat and was less troublesome. Today, coal is probably the most common, as the amount of charcoal one uses for even simple projects makes it somewhat cost prohibitive in comparison to a coal forge. Coal is somewhat uncommon these days, but not terribly hard to find, and we will cover resources for finding it later on in our article about fire building and management.
For a moment I would like to diverge here to discuss gas forges in passing, just so the reader will have a bit of familiarity with them until we reach that chapter.
Most modern gas forges are a box like object with a pipe or set of pipes on top, so they can easily be put in a number of places like the tail gate of a pickup truck for field work. A gas forge can be built into a table like a coal forge, or sit on a stand or mount at any convenient height for work in a shop. The forge box is lined with a fireproof refractory material, much more resistant to heat than common brick, and this makes these forges rather heavy for their size. The pipes that enter the top of the forge are gas jets, and have a system to mix fuel and air from the room together to produce a clean burning flame inside the forge box. Most gas forges are set up to run on propane, but any flammable gas that can be pressurized can be used (such as hydrogen, methane or natural gas). More on gas forges later though...
Once we have a forge and something to burn in it, we need to consider how to get that fire hotter than normal. This was originally done with a blowpipe. It works, but is pretty tedious and can make you quite light headed very quickly. So some clever smith came up with a way to build an automatic lung, which we today know of as a set of bellows. There were a number of improvements in bellows tech over the years, but in this modern age most smiths use a much smaller mechanical fan system. Heck, you can even use the output from a vacuum cleaner or a hair dryer, but both of these have interesting problems we wont cover here yet. Most of these systems have some way to control either how fast the fan turns or how much air it is allowed to push into the fire to better control the heat in the forge. Too hot can burn the steel and too cold will make many jobs much harder if not impossible.
This air system is connected to the underside of the forge with a section of fireproof pipe, and enters the bottom of the firepot through a specialized part of the bowl, usually called a tuyeer. (There are some variant spellings of this word.) Usually this section of the bowl also has a gate or some kind of door to allow the ash that falls out the bottom of the bowl to be cleared out.
Now that we have air in our forge, we have to do something with the smoke... that's where a stack and hood or some other system comes into play. Now if you are just outside, you can let the smoke drift away, but I have done this a lot, and I can tell you it will often drift right toward you (there really is a scientific reason too – you create turbulence in the air stream passing you, and the smoke can be pulled right to you even if you are up wind of the forge). Building a stack (or chimney) is a more complex process than it may at first look, but I will cover it in great detail later on, so do not fret. Connected to the stack is some kind of metal hood that collects and funnels the smoke, allowing it to leave the building through the stack. There are optimal ratios for the intake area vs the pipe size and stack height, and I will cover them in that article I just mentioned. For now, I just want you to be aware that most smiths use a steel hood over their forge, though some use what is called a sidedraft hood system. This is the system I prefer, and I will have a full article including pictures and plans up here soon as part of the aforementioned article.
That wraps up our lesson for today, and once we get past these most basic lessons we will begin to get into the real meat of it.
Until then, stay out of trouble.
The podcast for this will also be up at http://alonetone.com/ironangel under "albums and playlists - Blacksmith lessons".
This post will cover more specific details on the forge a blacksmith uses in their craft than our previous post “absolute basics” did. This resource will cover mostly coal forges, with gas forges covered in a later article. I will be leaving out the exotic and semi-exotic heating sources here, such as electric resistance heating systems and solar forges. These other systems are more specialized in their application and generally financially out of the reach for the average hobbyist smith. In later articles we will cover some simple variations of the modern and historical forges that can be built very inexpensively and in short order.
The forge is a place that the smith can contain and control a fire to heat metal up to working range, which is usually hotter than a normal camp fire. The term also often means the building the forge is located inside of, and the term “forging” is something made in a forge. Forgery is not the correct term for making something in a forge though... that would be smithing, which comes from smite; to strike something. You know... blacksmith, a smith who strikes iron, which comes from the ground and fire black, as opposed to gold or silver.
The history of metal smithing is a long and varied one, and forges have undergone many variations and changes over the passage of time. Originally, the forge was a simple hole dug into the ground, and a blowpipe was used to increase the heat of the fire. As time passed, the smiths decided that standing up was a lot more comfortable than crouching down to work in a ground forge, but a few clever smiths dug holes to stand in next to their ground forges, and in a few parts of the world these ground forges are still used today.
The next evolution was to make the forge a roughly waist high table, either of laid stone or brick. This allowed the air-blast to come into the forge from under the fire, instead of from the side or above, which increased efficiency and allowed the smith to get even greater temperatures from his fuel. There are variations during this long age, including forge tables built of wood and covered in clay, side blast forges and long trough forges. For simplicity sake, we will only cover the generic, basic forge here for now though and save the unusual ones for later.
In modern times, the forge is often built as a steel table with a heavy walled cast iron firebowl or firepot at the center of the table to contain the fire. This forge bowl is usually several inches deep and a bit more than a handspan across. This allows a decent amount of fuel to be used, yet is not wasteful. It also allows the solid sides to absorb and reflect some of the infrared heat back into the center of the fire, increasing efficiency.
In all ages, the area around the forge bowl is often used to hold extra fuel and lay out work pieces and tools. Careful fire management will keep the fire contained in the smaller, central pot so as to not waste fuel. Many smiths build special fittings into the table to aid their work. These can be tool racks, special dies for forming or bending, or workpiece supports for long rods of steel.
So why build a large, heavy table for a forge in this day and age? Forges are an efficient means of heating steel compared to other options, such as a simple torch with either a fuel air mix or a fuel-oxidizer mix. The fuel air torches are things like a propane plumbers torch which have only a single gas cylinder. A fuel-oxidizer system like a oxy-acetylene cutting torch, will have a pair of tanks. The problem with using either style of torch is the amount of lost heat that is simply blown into the room and not absorbed by the work piece. The amount of fuel used by either of these torches in medium to heavy blacksmith work will make them prohibitively expensive in short order.
That about covers the basics of the forge, now we need to look at the fuel, air input assembly and the hood or draft system to remove smoke and heat.
Historically, forges burned coal, charcoal or in some rare cases peat moss as fuel. Raw wood is generally not clean burning enough to be used as is, so it was usually rendered down into charcoal, which gave a better heat and was less troublesome. Today, coal is probably the most common, as the amount of charcoal one uses for even simple projects makes it somewhat cost prohibitive in comparison to a coal forge. Coal is somewhat uncommon these days, but not terribly hard to find, and we will cover resources for finding it later on in our article about fire building and management.
For a moment I would like to diverge here to discuss gas forges in passing, just so the reader will have a bit of familiarity with them until we reach that chapter.
Most modern gas forges are a box like object with a pipe or set of pipes on top, so they can easily be put in a number of places like the tail gate of a pickup truck for field work. A gas forge can be built into a table like a coal forge, or sit on a stand or mount at any convenient height for work in a shop. The forge box is lined with a fireproof refractory material, much more resistant to heat than common brick, and this makes these forges rather heavy for their size. The pipes that enter the top of the forge are gas jets, and have a system to mix fuel and air from the room together to produce a clean burning flame inside the forge box. Most gas forges are set up to run on propane, but any flammable gas that can be pressurized can be used (such as hydrogen, methane or natural gas). More on gas forges later though...
Once we have a forge and something to burn in it, we need to consider how to get that fire hotter than normal. This was originally done with a blowpipe. It works, but is pretty tedious and can make you quite light headed very quickly. So some clever smith came up with a way to build an automatic lung, which we today know of as a set of bellows. There were a number of improvements in bellows tech over the years, but in this modern age most smiths use a much smaller mechanical fan system. Heck, you can even use the output from a vacuum cleaner or a hair dryer, but both of these have interesting problems we wont cover here yet. Most of these systems have some way to control either how fast the fan turns or how much air it is allowed to push into the fire to better control the heat in the forge. Too hot can burn the steel and too cold will make many jobs much harder if not impossible.
This air system is connected to the underside of the forge with a section of fireproof pipe, and enters the bottom of the firepot through a specialized part of the bowl, usually called a tuyeer. (There are some variant spellings of this word.) Usually this section of the bowl also has a gate or some kind of door to allow the ash that falls out the bottom of the bowl to be cleared out.
Now that we have air in our forge, we have to do something with the smoke... that's where a stack and hood or some other system comes into play. Now if you are just outside, you can let the smoke drift away, but I have done this a lot, and I can tell you it will often drift right toward you (there really is a scientific reason too – you create turbulence in the air stream passing you, and the smoke can be pulled right to you even if you are up wind of the forge). Building a stack (or chimney) is a more complex process than it may at first look, but I will cover it in great detail later on, so do not fret. Connected to the stack is some kind of metal hood that collects and funnels the smoke, allowing it to leave the building through the stack. There are optimal ratios for the intake area vs the pipe size and stack height, and I will cover them in that article I just mentioned. For now, I just want you to be aware that most smiths use a steel hood over their forge, though some use what is called a sidedraft hood system. This is the system I prefer, and I will have a full article including pictures and plans up here soon as part of the aforementioned article.
That wraps up our lesson for today, and once we get past these most basic lessons we will begin to get into the real meat of it.
Until then, stay out of trouble.
The podcast for this will also be up at http://alonetone.com/ironangel under "albums and playlists - Blacksmith lessons".
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