Blacksmith Lessons – The Side Draft Forge Hood, part 2

Part one is here.

In our last lesson we covered laying out your pattern in cardboard. Now it is time to start building the real deal. The hood can be built from any spare sheet steel you have about, ranging from 16 gauge up to 1/4” thick plate stock. The thicker the material, the heavier it will be and the more difficult it will be to install and move your forge after it is in place, so keep that in mind. Ours is made of 1/8” plate from the scrap yard and cost us about 50 dollars US when we built it. All the steel does not need to be the same thickness either; if you have a mix of thicknesses, you can still build the hood.

If using mixed weight steels, your front, top and back take the most heat and strain, so you may want to use thicker stock for those. The base takes the least stress, so you can use lighter steel here. As the box heats up, the back wall may flex and make a heck of a bang, throwing dust and ash about and surprising you. Thicker steel or reinforcements (covered later) will help to prevent this.

Once you have your steel, take your cardboard patterns and either a marker or chalk and lay out all your parts. If needed, you can join two or more smaller pieces to make a section large enough for your use. If you do have to join plates, make sure the joint is airtight with either close set rivets, or a weld. Be aware, a single long, straight weld is likely going to warp the steel, so you will have to weld a few inches, move to another section of the joint and weld there and so on until the entire joint is welded to reduce warping. Rivets look great (very steampunk!) but a weld is easier to get airtight.

Once your pieces are laid out, cut them to shape using either a cutting torch or plasma cutter, or if in thinner steel some kind of metal cutting shear. Thinner steel will be harder to weld and may require some unusual modifications to the techniques given here to work. If needed, clean up your cuts a bit with an angle grinder or file, but be careful to not cut too much metal away. Having extra metal is far better than too little, as you can always grind or file away, but adding a bit is more tricky.

These instructions assume you are welding all the parts together. You can, however, use sections of thin 16g steel cut into long, 3 to 4 inch wide strips, folded to 90 degrees lengthwise and a LOT of rivets to rivet the entire hood together. Pop rivets are not as strong as hammer set rivets or roofing nails clipped short (which make workable make shift rivets and are less expensive by far). And this has not been tested with pop rivets either, it may well not work!

With your pieces cut out, you are ready to begin assembly. Start with the base plate and the back plate. Lay the base plate flat on a welding table or concrete, and place the back plate in place. It will need to be braced to keep the joint at 90 degrees the entire length. Tack it in a few spots on the inside and outside with 1” long tack welds. We welded ours entirely from the inside along the lower joints, you may as well, or turn the assembly over and weld from the outside. The inside welds allow the box to sit flatter on the forge table however.

With this weld complete, check the joint for square, and adjust if needed, then weld in one side piece. Again tack in a number of places before welding to help reduce any warping or shifting. You may want to tack the other side in place as well and test fit your front piece just to be sure everything fits. It will be easier to correct a problem now, with everything just tacked, than once it is welded in firmly.

Our hood has a section of light weight angle iron along each upright corner to make it look better, and add some strength to the structure. It is welded in place from the inside, tacking it in through a couple holes drilled at an angle through the corner joints. Once our corner covers were tacked in place, each corner was welded from the inside full length in one pass with enough heat to penetrate somewhat into the angle iron. You do not need to be this aggressive about it, as long as the joint is airtight. It can also be “skip welded”. That means you can weld a section, move to another and come back once the first weld has cooled, so long as the joint is clean and solid.

Next we suggest adding the extension to the face of the front. We welded this on from the inside as it looks better. With that in place, we welded the front on. Here is where it begins to get tricky, as you will have to lay the tacked assembly on its face and nearly climb into it to weld the bottom joint and the lower part of each upright joint. And you may have to support the front with bricks and connect your arc welder clamp directly to the assembly to keep the whole from rocking with the front shroud already in place.

Once you have the lower assembly together, you may want to weld in a pair of bars from the front to back plates to keep the walls from flexing. Angle iron works well here, with one section mounted on each side of the top of the intake opening. Putting a single bar across above the opening is not as effective, and heat will probably cause it to flex over time. These support struts are not critical, and are completely optional.

If you have decided to put in the angle plate that directs smoke upward, put it in and tack it in now. It does not need to be fully welded into place. Just make sure the front edge at the inlet is welded flush with the bottom so there is no gap.

Now that the lower assembly is complete, the upper half will now be assembled. This will be a little tricky, but not horrible.

First, tack the collar and check to make sure your pipe will flex and fit over it tightly. Then weld the collar into place and tack the top plate at 90 degrees to the back plate. Make sure the collar is on the outside! This plate will make lining up the rest of the plates a lot easier. Lay the assembly on its back, and fit and tack the front upper into place, then each upper side. If they are curved, you may have some fun trying to match the curves so the joint it tight and easy to weld. A heavy pipe in a heavy vice is one way to allow you to form the curve; just hold the steel over it and strike beyond the pipe with a wooden or rubber hammer. You can also put it across two bricks and stand on it, or if all else fails, drive over it with a car. Be creative but safe!

With all the parts tacked in place, weld all the uppers from the outside. There are some long welds here, so take your time and do a good job, as these will show. Once you are done with the welds, you can take an angle grinder and smooth your welds if needed.

Your side draft hood is now done! Now you (and probably a friend) will have to move it into place on your forge bed. Watch out for pinched fingers! If you like, the hood can be raised a bit with a layer of brick, and this can aid in creating a better draw, but is not critical.

Once the hood is in place, mount your riser pipe up to your stack (or straight up through a collar in your roof if in a shed or the like) making sure all is firesafe and sealed (another much larger topic!!). With that, your hood is ready to use.

We will cover making the “flip up hat” part in the next post, though you may want to make it and mount it before you install your hood. It allows you to suck up much more smoke when you first light the forge.

A few notes on using the side draft hood-

Before lighting the forge, put a ball of paper in the intake of the hood and light it to pre-warm the air and start the draft.

With the forge first lit, when the most smoke pours out, you may need to place a thick plate of steel on the forge angled up to the intake hole on the hood to get the hood warmer and suck up most of the smoke.

Once the hood is warm, the draft will be more effective. As soot and ash seal any tiny holes in your stack and hood, it will draft better. The more airtight the hood and riser pipe are, the better the draft. In fact, the draft can get quite strong. In the right situations, ours will suck up a piece of paper left on the forge table (much to our surprise). The trad off here is it will also suck any heat out of the room. You may need to make a cover for the intake for times you are not using the forge to prevent it from drawing all the heat out of your shop in the winter.

Once the hood is drawing well, you may notice the flame rising above the forge bending at a steep angle into the hood! Just because the heat is not rising directly does not mean the infrared coming from the forge is not... if your ceiling beams are low and wood, you may need some kind of heat shield still.

The forge hood will get warm in use, and in heavy use it will get hot. Be careful about brushing against it, as it can burn you. Also make sure it is well away from walls and nothing flammable is leaning on it.

A larger intake opening will still draft, though not as well. If you only have an 8” exit stack, you can still have a 12” by 14” intake with a tall chimney and good connector pipe. It will not draw as effectively, but it will still draw.

On some days, when the atmosphere is right and the hood is warm enough, you may hear a faint rumbling as air is drawn into the opening. This is normal and not a problem. If it is quite loud, something is amiss or something else in the shop is causing it. The large, flat walls of the hood may be resonating in sympathy with something else in the room. Try sticking a large magnet to the side, off center, and see if that stops the sound.

That about covers it for now, images and part three coming soon!

Colonial forge part 2

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.

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.

Blacksmith lessons – The bucket forge part two

Hello again all, and welcome to part two of the bucket forge lesson. In this lesson we will get some air into your bucket forge. If you happened upon this document, the first part can be found at http://ironangelforge.blogspot.com/ and the audio version can be found at http://alonetone.com/ironangel/playlists/blacksmith-lessons

The bucket forge is a very primitive little bugger, so no sense in cluttering it up with a good quality air source. We will cover those later in more appropriate sections. For this project quick and dirty is the best route.

Any item that moves air will work here, but first a quick concept must be explained to better help you choose which item you will use. For a forge, high pressure flow is not needed, and in many ways is more of a problem than you might expect. High pressure air can blow the lit coals right out of the forge, and this makes working far more challenging. High volume at low pressure is more useful, which a proper set of large and heavy blacksmith's bellows will produce. But for our small bucket forge, low pressure and low volume are probably enough to allow you to get going and start making needed equipment.

There are a number of quick and dirty ways to get low pressure, low volume air into your forge. A very common one is to put a hairdryer at the end of the inlet pipe, laying on it's side on a brick or stack of boards, and this can be quite effective. To vary the amount of air it pushes into the forge, move the end of the hairdryer closer or further away from the end of the inlet pipe. Closer will focus more air into the pipe. If you go this route, get a cheap hair dryer from either a yard sale or the salvation army. It is even better if it doesn't have a working heat system, or has a “no heat” setting. The problem with the heat system is this; the coils will draw more current, making your set up less efficient, and can overheat causing the hairdryer to shut off on its own, or if you are very unlucky, melt down and fail entirely. If it is a particularly weak hair dryer, you could tape the end of the dryer to the inlet pipe on your bucket forge.

Another option is a desk fan and a cone made of cardboard or the like. This is very primitive, but it can work fairly well considering what it is. Here, the end of the cardboard cone is simply taped over the end of the inlet pipe and the fan is set before it blowing into the pipe. Shoving the end of the cone into the pipe will restrict airflow quite a bit, and may block it off completely. Make sure your fan is set to not oscillate back and forth as well. It can easily knock your cone off, and wont funnel as much air where you want it. Also be careful to not set your cone on fire with falling bits of metal or the like.

There are as many other options as you have creativity to find or build; the cone system could even be used to catch the prevailing winds, but this will be harder to control and somewhat inconsistent, and doesn't work well on a calm day.

There are a couple things I can definitely suggest NOT using, including air compressors (high pressure, and they can be high flow – they tend to blow the fire out of the bucket all over you and the local area), leaf blowers (same problem, perhaps even worse than air compressors) and many large shop vacuums. Though a shop vac can be made to work by restricting how much air it is allowed to intake, but that is another project for another day. They also tend to be very noisy.

That covers this short section on getting air into your bucket forge, next is the larger colonial forge. Stay tuned!

(note, the reference to the rocks mentioned in the previous post has been omitted and will be covered in the next post - it applies to both forges)

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.