forge material questions

Godspeed

Godspeed

Well-Known Member
So I've decided to make my first forge.
I don't really have any specifics, so i need to be steered into the right direction here.
I want something small and efficient as possible (of course), It will only be used for knifemaking and maybe other small projects.
So i'm thinking round instead of square.
my rough idea is 8" round and 10" long, with 2" of insulation all around to give me a 4"x6" chamber... Is that too small? If not, how small can i go?
I suppose i could use an air tank or something like that for the shell but I would rather make the whole thing that's the kind of guy i am :les:
I work in a sheet metal shop so i have access to shears, rollers, brakes, welders etc...We have some 12ga black iron but I really want to make it out of 16ga stainless. It is my understanding that the outside doesn't get all that hot, so would the stainless be an acceptable material for this?
Also, what sort of burner set-up would be ideal for a chamber of this size? I'm assuming the smaller the chamber; the less heat needed?

Any help would be greatly appreciated.
-Adam
 
Godspeed said:
So I've decided to make my first forge.
I don't really have any specifics, so i need to be steered into the right direction here.
I want something small and efficient as possible (of course), It will only be used for knifemaking and maybe other small projects.
So i'm thinking round instead of square.
my rough idea is 8" round and 10" long, with 2" of insulation all around to give me a 4"x6" chamber... Is that too small? If not, how small can i go?
I suppose i could use an air tank or something like that for the shell but I would rather make the whole thing that's the kind of guy i am :les:
I work in a sheet metal shop so i have access to shears, rollers, brakes, welders etc...We have some 12ga black iron but I really want to make it out of 16ga stainless. It is my understanding that the outside doesn't get all that hot, so would the stainless be an acceptable material for this?
Also, what sort of burner set-up would be ideal for a chamber of this size? I'm assuming the smaller the chamber; the less heat needed?

Any help would be greatly appreciated.
-Adam
Click to expand...


Adam,
Check out my forge build thread
http://knifedogs.com/showthread.php?15480-Adding-a-blower-to-a-forge.... if the link doesn't work it's in this sub-forum,
there is a lot of info in all these posts, hope this helps, Rex
 
The frame of my large forge that I use for heat treating is made from a large mail box. The 4X6" chamber will work fine but I think that it will end up a little larger than than. You will probably be better off if you make the "doors" at the front of the forge out of fire brick. Even if you fabricate a swinging metal door on the front of the forge it will not enter the chamber of the forge but be mounted on front of it, either instance will make the fire chamber 4X8". If you construct similar doors on the back side you will add another 2" to the depth of the forge. I recommend that you put a pass through port on the back side of the forge whatever way you construct the forge. This will allow you to forge any length of blade that you want and will heat treat a blade a few inches longer than the depth of the fire chamber.

Doug Lester
 
Round is the only way to go ( no hot spots ). Go to Indian George's web site, he has plans for his forge. Looks like a winner. Keep in mind that if you get the damascus bug you will need a style that the flux won't destroy.
 
I have one made out of flu pipe, its dirt cheap and easy to do. I am working on a 2 stage PID controlled forced air unit like one of the guys on here did, I decided to make the forge body a bit larger as the 8inch pipe is just a bit to small for what i want to do.
 
Thanks guys!
I"m planning on basically making an 8" stainless pipe and capping the ends off, then dropping back 1'' on each end and cutting it off to give me 1'' thick doors to line. Would a 4''x4" port in each end be adequate? I suppose i could use some 4x4 square tubing to make a lip on each port. Also another question... would a flat bottom inside benefit me? I was thinking i could use fire brick in the bottom, that way it could be replaced if need be from the flux getting on it. Would this size forge benefit from two burners? or maybe one split into two small ones?
also, the only place i have to put it will be on a wooden table, so how tall should I make the legs?
Sorry for all the questions, but I figure you are the guys to ask.
Thanks again,
Adam
 
Round is my vote also. 8" is what I would recommend. As to length, about 16" is the most you can efficiently heat with a single ventrui type burner. Beyond that length will require either more burners, or going to a blown burner.

Now, let's discuss the closed ends....I recommend NOT enclosing the ends. The reason? A forge must be able to "breath". Essentially a gas forge in nothing more than a controlled explosion, trying to build one that is, or can be "sealed up" creates a lot of issues, the least of which is being able to control the forge. Enclosed ends might look "neater" or "cleaner" but in many ways you're painting yourself into a corner. If you feel that you must enclose the ends, build the "caps" with an opening on each end that you can block with either a fire brick or a chunk of ceramic wool. It may not make sense now, but once you start using the forge, it will.
Another reason to NOT cap off the ends of a forge is that sooner or later your going to have to reline it....and it's MUCH easier to reline the interior with a single piece of ceramic blanket, than it is to have to "patch work" everything.

A fire brick "slip" is the way to go for the floor. It's basically a fire brick that has been sliced in half lengthwise (1/2 the thickness of a standard hard fire brick). I forge nearly every day, and replace mine about once a year.

Next, this is going to sound counter-intuitive, but using 1" of ceramic wool will be more fuel efficient that using 2" thick. Without getting into a long winded explanation on the characteristics of ceramic wool, I can tell you that I have tested both 1 & 2" wool in the same forge bodies.....2" will take longer to heat up, and will require a high fuel psi setting to maintain the same temp when compared to 1". Most folks think they are adding insulation and saving money by using 2"...I used to think that way too, but after adding up the cost of 2", and discovering that it takes 2-4 more psi to maintain temp (meaning it requires more fuel), I've chosen to revert to 1".
 
Check out Ron Reil's web site. There is more information their than you ever wanted or even thought existed. You find it by going to www.abana.org then go down on the left side of the page for
[FONT=verdana,helvetica]Access Ron Reil's Site HERE.[/FONT]
Ron tells you that you need the back of the forge open for back pressure relief..Kinda like a car runs better with some back pressure but not with no back pressure.
I would not suggest using uncoated ceramic blanket anywhere (remember is is called "CERAMIC BLANKET." Read "ceramic" as "glass". Ceramic blankets are similar to fiberglass insulation. Fibers do detach and float around in the air, and you have the turblance of the flame to help blast these fibers out into your shop. Do you really want to be breathing glass?). Use ceramic blanket for insulation with an insulating cast refectory over that. I suggest having the blanket covered on each end by the end of the forge (the reason I like using propane or freon bottles. This encloses the blanket. Hard Fire Brick is a heat sink. Put blanket in the floor and cast over it with Kast-0-Lite insulating refectory. It is also resistant to flux. Remember, flux is not glue. Use it sparingly. You should not have globs of flux falling off of the metal onto the floor, although you will invariably have some get onto the floor. I have ceramic pieces that I use on the floor of my forge to hold metal up in the circulating air to better heat the metal or ones that will hold two blades vertical (edge up or down). These are only $2.00 each and the flat ones are shaped like an I beam and are about 4" square. The ones to hold the blades up are about 3 inches long and will hold 2 knives. After all, you can't forge more than 3 knives at a time and that will work you to death. No breaks in there.
 
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Wow. I'm learning alot here.
I need to draw up a diagram of what i'm talking about.
i meant that after capping it off to drop back 1'' on each end and cutting it
thus making 1'' thick doors on both ends, and then cutting 4''x4'' holes in the doors.

Ed, If I didn't know you were a Mastersmith, and have watched one of your DVDs I wouldn't believe you about
1'' liner working better than 2". I'll take your word for it though.

I'm going to visit Wayne in a few weeks, i'm sure he will get me straightened out.
And thanks Wayne for that link! LOTS of good info there.

Another question: What angle does the burner need to go in?
Isn't it supposed to go in at an angle so the flame will sort of roll on the opposite wall
and smooth out?
 
Ok so instead of just drawing it, I went ahead and built it.:les:

here is the body all welded up. 14'' long x 8'' round.
forge1.jpg


I then dropped back an inch on each end to make 1'' thick doors, that way i can use 1'' inswool to line them. here it is all marked up.
forge2.jpg


And here is what it look like after cutting the doors off. I now have an 8''x12'' chamber and two doors.
forge3.jpg

i'll weld on some flanges so i can unbolt them when i re-line it or need to get in there for something.

After that i marked a 4"x4" square (starting about 2 1/2" from the bottom to clear the fire brick) that I will cut out.....
forge4.jpg

and weld in a 4''x4'' channel that will stick out about 3/4" on the inside and outside of the door and help support whatever I am forging. I stopped here in case I'm doing something wrong, or i forgot something.

How is this looking guys?
 
Looking good to me! I for one like having the channel entry that kind of works as a shelf for me.

Ed, I have a question, as Im in the process of building a new shop and all the assorted equipment. If you used 1" of wool insulation inside the forge, with satinite and ITC100 coatings, but then insulated the outside of the forge, would you still have the same issue as described above? Would the exterior insulation act as a heat sink? I have access to some mastic type insulation thats good up to 1800 deg thats used on piping in the refinery, just wondering if it would help or hurt??

God Bless
Mike
 
Can someone tell me how to figure the chamber volume of the forge i'm building? allowing for 1" of inswool makes it 6" round by 12'' long.
I came up with 432c.i. but I don't have a clue if i'm doing it right.
 
Godspeed said:
Can someone tell me how to figure the chamber volume of the forge i'm building? allowing for 1" of inswool makes it 6" round by 12'' long.
I came up with 432c.i. but I don't have a clue if i'm doing it right.
Click to expand...
Pi times the radius squared, times the length will give you your volume, which will calculate out 339 cubic inches volume, this is assuming your forge body is 8 inches in diameter, which will give you 6 inches diameter inside of the wool.

alternatively: you can use this
 
Thanks guys.
I forgot to take some off for the flat bottom. so it will be less than 339. I'll lay out a side view and recalculate.
 
OK so I now have my forge up and running!
(major thanks to Wayne Coe)
I'll post some pics of it when i get a chance. I think I still have
alot of tuning to do.
Long story short ......
I FORGED SOMETHING!!!!
forgedcross.jpg
 
On both of my gas forges the burner tube goes in horizontally but about half way above the mid line of the chamber. That way the the flame strikes the opposite wall of the forge at an angle to the curve which causes it to swirl in the chamber. Others might mount their burners slightly different. One thing that you don't want is for the flame to be directed down onto the floor of the forge. It works for general blacksmithing but it's not good for knifesmithing. It causes hot spots that gives trouble when it comes to heat treating.

Doug Lester

Oops! I guess that I didn't see the last post. Nice looking cross, by the way.
 
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I still forge blades directly in the flame or when I forge with coke I lay blades directly on the white hot coals?? smiths have been making blades that way for thousands of years yet they have produced many fine antique blades . Personally think its just a matter of choice . japanese smiths of old forged on open flames for at least a thousand years. As a matter of fact it is a preferred method to heat the edge directly in the flame ,Its how double hamons ( utsuri) are produced , by having the edge exactly 100 degrees F hotter than the rest of the blade . The swirl on a round forge does look purty though. the real key is to keep the blade moving . respectfully Bubba

http://www.ksky.ne.jp/~sumie99/utsuri.html
 
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