Jump to content

First Forge Build Questions (insulation, burner angle, safety tips)


Recommended Posts

Hi I am getting geared up for building my first forge this December. I have a couple of very newbish questions.

 

I want as safe as a forge as possible, I am relatively new to this and want to give myself the most safeguards possible.

I want a forge capable of forge welding, and may eventually play around with melting brass, copper, and silver.

I want to be able to heat treat knives with it.

I want as precise of temperature control and information as possible.

Fuel efficiency is plus.

 

So my basic understanding is

 

1. Get a solid metal casing (such as a old propane tank, or air compressor). Looking for a 10" to 12" diameter tube.

 

2. Line with Kaowool or a similar material.

3. Leave an area on the bottom open and line with refractory mortar and firebricks.

4. Cut a hole for your burner, but a smaller opening for the back.

5. Line the Kaowool (2-3 inches) with ~1/2" of saronite, then a ir reflective refractory clay. (partially fire up the furnace a at each layer to cure the clays)

6. Weld in a housing for the burner, attach to a propane tank and you are good to go.

 

7. Where wool/cotton cloths, a respirator, and face shield when working with dangerous/hot materials

 

So my questions.

 

1.

a. Can you use something other than the ceramic fiber insulators (like a castable refractory)

b. Is the a substantial difference between the different ceramic fiber insulators

c. Is there any benefit to going for the 2700f rated materials over the 2400f rated ones

 

2. Any major differences between the types of firebricks, should I put a lining of ceramic fiber underneath the firebricks or just leave them and the mortar as the base?

 

3. What is the purpose of the hole in the back, should I have a door to completely cover it when I want heat retention.

Should I try to include a "porch" at the front to setting work on when working in the forge

 

4. What angle/height should the burner be at right now I am leaning towards the 1" forge and foundry burner from hybrid burners.

How deep should the end of the burner be set relative to the innermost layer of clay.

 

5. Does anyone know how the hyb-uv infrared reflective coating compares to ITC 100, and other final coats, how much does thickness matter (if you go much thicker will you get much better heat retention?)

 

6. Do you line hole the burner goes though with saronite/ITC 100 as well, any tips on the final attachment of the burner. (this is the part I am most uncertain about the details on)

 

7. I have heard people recommend the soft copper for the line carrying the propane is this sound advice?

 

8. Any advice on where to mount a thermocouple and where to mount it (should I mount more than one) to get a good idea of the heat and heat distribution in the forge. (also what brands of thermocouple would people recommend). (I know this may not be strictly needed, but I have a background in physics/math and like/use the information and it sounds useful especially for heat treating.

 

9. Anything basic/important that it looks like I am missing or general safety tips, the unknown unknowns are always more dangerous that the dangers you know about and prepare for.

 

Thanks in advance for any help.

Link to post
Share on other sites

Pretty much everything you want to know has been covered on the forum. Looks like you are new here (this was your first post), so welcome! You will find more information here than you will know what to do with for a few years, at least. The best piece of advice I think any new forum member can get is to use Google site searches rather the built in forum search tool.

 

Start here: site:bladesmithsforum.com forge design

 

After you read the first dozen or so result threads, change the "forge design" part to more specifically address your remaining questions. I would also recommend searching for the terms regulator, venturi, blown burner, vertical forge, horizontal forge, and refractory brick/blanket.

Link to post
Share on other sites

 

I want a forge capable of forge welding, and may eventually play around with melting brass, copper, and silver.

I want to be able to heat treat knives with it.

I want as precise of temperature control and information as possible.

Fuel efficiency is plus.

I'll leave you to do your reading, but I do have a couple things.

 

1) A forge for making knives and a casting forge are different animals. While you could design a forge to do both things, it would be better to build more than one, each optimized to the task.

 

2) Same issue. I use a vertical forge with about a 6 inch hot zone to make my blades in, even the long ones. I have a second forge AND an electric HT oven for HT'ing blades. This feeds into

 

3) Thermocouples are pretty cheap, how you implement them can be very complicated and expensive. You could build a system that uses a thermocouple, solenoids on the gas lines, and some kind of PID to control it all and get a high degree of temperature control. Is that going to make a better knife maker? In your reading include Electric heat treat ovens and Salt Pots.

 

4) This last one is something we talk about a lot. We haven't come to any conclusions, but we talk about it. How do you measure "efficiency"? Pounds of fuel per hour? Cubic feet per minute? Cubic inch of material heated to X temperature in X time? Blades forged per hour? The most efficient "forge" might be an induction coil in terms of run time per inch of steal heated. However, the cost per blade is pretty steep, at least starting out.

 

I'm not trying to be flip, you've managed to drop into the middle of a long standing discussion. After you've done some reading, build yourself a simple forge, don't over think it. Work with that for a while, find out it's strong points and weak ones. Build another one, or more, that do it better, or at least differently.

 

Here is the question I ask myself every time I go to the shop. Do I want to be a tool builder today? Or do I want to make knives.

 

Geoff

  • Like 1
Link to post
Share on other sites

Check out the two attachments on the Forge Supplies page at www.WayneCoeArtistBlacksmith. This will show you how I like to build a forge that will be efficient, tuff, and long lasting. The Build a Gas Forge will answer most of your questions. For your requirements I suggest that you look into using a Ribbon Burner which is the second attachment.

 

Let me know if I can help you.

 

Wayne

Link to post
Share on other sites

There are plenty of threads here on forge building and more discussion and opinions than you can point your mouse at.

Take Geoff's advice: After you've done some reading, build yourself a simple forge, don't over think it. Work with that for a while, find out it's strong points and weak ones. Build another one, or more, that do it better, or at least differently.

 

Most of us have gone through a couple of forge designs and the truth be told, they don't last forever and sooner or later you will find yourself either rebuilding the one you have, or scrapping it and building a new and better version. How that new and better one is designed, how it works, what it is used for, etc. is all going to be modeled on your preferences formed by your experience. Each one of us (who has been at this for a while) is going to give you different answers for each of those questions based on our preferences formed by our experience. And you will end up no better off than you are right now.

 

If i were to answer your questions it would come out like this:

1. Yes. you can use castable refractory. Define "substantial" and do you prefer Ford, Chevy. or Doge trucks?

2. Yes. there are differences between types of fire bricks.

3. To slide long pieces through the forge so you can heat the center section rather than just the ends. Put a door on if you like. I highly recommend a "porch" or other support (preferably adjustable in length).

4. I do not think it matters much. Just make sure the flame is in the forge body not in the refractory.

5. Less refractory (1" is plenty) is better than more. This stuff reflects heat once it is saturated. Heat that it sucks out of the forge.

6. Look at other designs on the thread Jerrod posted. Used the design you can create easily.

7. Use line that is made for fuel gas. It doesn't much matter what it is made of, as long as it is rated for fuel gas.

8. Skip the thermocouple for now. Train your eyes and other senses to detect the state of the hot steel. I have been at this for a decade and I still don't have one.

9. Tons of them, but most of them won't kill you as long as you are aware of the fact that you are building something that most "normal" people would run away from if you brought it to their house. This is dangerous business no doubt. If you have never been to another smith's shop and used his/her forge, talked with them about how it works and what the intricacies of the design are, stop right now and get yourself in front of one of these things with an experienced user. Or you could damn the torpedoes and go for it. Your choice.

Link to post
Share on other sites

There are soft fire brick and hard fire brick. The soft ones are more insulating and make good doors but flux will eat them for lunch. The hard fire brick give better thermal mass but take longer to heat up but they are more resistant to flux and therefore make a better floor for your forge. The ceramic matting, Ins-wool or Kao-wool, are the same thing. Make sure that it's 8#. You can coat the matting with a castable refractory such a Mizzou or Cast-O-Lite to protect the fiber from being punctured with a blade and to protect you from inhaling fibers from the matting once it's been exposed to high heat. Very bad for the lungs. A refractory is better than Satanite, which is as mortar, as they are more durable.

 

Doug

Link to post
Share on other sites

I think the best advice you've been given is to see one in action and talk to the person who owns it. That said, where are you? There are likely smiths near you. We are like spiders, we hide out in the damndest places.

 

Geoff

Link to post
Share on other sites

Thank you for the replies.

 

I do have one blacksmith I know near me and I have been trying to set up a time to go see him in action, and making that a big priority definitely seems like very sound advice. I have done quite a bit of reading already but there is always more to learn, the keywords to search for are very useful as was Joshua's point by point.

 

I am in Southwest Texas (a bit over an hour west of San Antonio).

 

Lastly has anyone used hyb-uv infrared reflective coating (from the hybrid burners site). I have done several searches and outside of the page he sells it on I can't seem to find much in the way of information on it.

Edited by David R B
Link to post
Share on other sites

I just read back over our post and noted that you want as much temperature control as possible. I know that that's relative but forges aren't big on precise temperature control. Yes, you can adjust them, if well designed, to run at let's say 1700° or open the burner up wide and get up to welding temperature at 2200° but if you want precise temperature control, like within 25°, you're really looking at a high temperature electric oven.

 

Doug

Link to post
Share on other sites

Measured how? What degree of precision? I can dial my main forge in where I want it within 200 degrees, at a guess, by eye. In my HT forge I can get 1600-1700 degrees measured by thermocouple, but it's hard to hold it that low, it tends to creep up. I can get any temp the controller will take (I've tried temps as low as 500 and as high 1800, I don't know what the stated limits are) and hold that for as long as I want +/- 5 degrees.

 

I like ribbon burners just fine, but it's not precision unless you can put a number to it and account for errors in the measurement process.

 

I would like to know how low you can get a stable burn in your ribbon burner,

 

Geoff

Link to post
Share on other sites

Geoff,

One man's stable is another man's .........well, not stable.

I have posted this before and I'll do it again. The most effective way I have found to control the heat in my forge (talking blown burner or blown ribbon burner) WITHOUT a lot of fancy thermocouple/PID electronics, is with this set up:

Gas valves (2)_opt.jpg

 

Working from the left to right in this photo. The 100 lb gas tank, adjustable regulator, pressure gauge (all on 1/4" galvanized iron pipe) step up to 3/4" Tee fitting. One side of the Tee (the yellow shut-off valve) goes directly to a NC Tools Whisper Daddy 3-burner Venturi style forge. The other side of the Tee is where I have my blown burner set up. First you will see the red handle of a 3/4" ball valve then a step down back to 1/4" and a 4-position ball valve. This has physical detents to tell you what percent of open you are (25, 50, 75, 100%) that goes into a 1/4" needle valve which feeds into a system of air/gas mixing with the blower to feed the ribbon burner.

 

How I get my control:

Starting with all gas valves fully closed, and a fire extinguisher handy, turn on the blower.

Open the air flow to about 50%. Turn on the tank and set the regulator to about 3.5 pounds.

 

1. Open the main shut-off (red handle) but keep your left hand on the handle!

2. Open the needle valve a few turns.

3. Set the 4-position valve at 50% while holding the ignition source (propane plumbers torch) in the front opening of the forge.

4. Light the forge.

5. If it goes KABOOM! shut off the red handle and get the fire extinguisher. If it fails to light, take your other hand off the shut off and start to open the needle valve until it does.

6. With the forge running, start adjusting the air gas mixture (gas at needle valve) until the inside of the forge looks like the color of steel that is ready to forge. (bright red to dull orange) If it starts to creep up or down, adjust the gas/air mix until it remains steady.

Congratulations, you have just "tuned" the forge to operate at a set forging heat.

 

Want it hotter? OK, open the 4-position valve a half click and open the air mix a half turn. Want it hotter? Repeat the last process. Judge the forge heat by the color of the refractory. Want welding heat? On my forge that's 75% open on the 4-way valve and a full turn more open on the air. To get back to forging heat, I simply close the air a full turn and close the 4-way valve to 50% again and I'm right back where I wanted.

 

Once I get the gas/air mix figured out for basic forging heat, I NEVER TOUCH THE NEEDLE VALVE AGAIN. All my gas volume is controlled at the 4-way valve. Air flow is controlled by a gate valve and never really adjusts more than a full turn in either direction.

Link to post
Share on other sites

Reminds me of Bill Cosby and his AC Cobra. My setup is different. I have a black iron pipe the runs from a 140 lb tank around 2 walls of the shop with "T"'s every 8 feet. There is a regulator on the tank which goes to a main shutoff (which I've never had to use). Each plumbed "T" has a 1/4 turn shut off, then a needle valve to the burner. I use a shutter on the fan intake to control the air.

 

To light I open the valve on the big tank, open the regulator to about 2psi, light the torch, switch on the fan, open the 1/4 turn valve, and crack the needle valve until it lights. If I need more burn, I open the shutter and needle valve until I get the color in the forge I want. Less, close the shutter and needle valve. To do minor adjustments to the burn, I make little adjustments to one or the other. Mostly I adjust it right at the start, and then never touch it again during the session.

 

Geoff

Link to post
Share on other sites

Geoff I do have a Pyrometer that I use when I am doing fluxless welds (I shoot for 2315 degrees F) or when heat treating. I insert the metal and watch the Pyrometer display for the temp and adjust the gas/air mixture to get the desired temp and atmosphere. I have to watch it pretty closely until the interior of the forge has soaked. After that the temp stays about the same until I am ready to take the metal out. When I put the metal back in the temp will drop until the metal has come back up and everything has equalized. I am running about 1/2 # of Propane pressure.

Link to post
Share on other sites

Tom, I really don't have a good idea. If I forged every day, when would I get anything finished? That is assuming that I do, occasionally, finish something :rolleyes: , The truth is, a weeks worth of forging is probably months of finish work. For my everyday forging needs a tank that size only gets filled a couple of times a year. As an example, I fired the forge to make a bent bracket for a project, I haven't forged really at all since the Spring, when I had a shoulder rebuilt. After I made the bracket, I took a piece of steel (well the fire was hot, it shouldn't go to waste) and forged up what is going to be a knuckle guard bowie with a 15-16 inch blade. That took about 30 minutes, using mostly the power hammer and press. Then I shut down. That piece probably won't get off the bench until next year.

 

If I'm making damascus, I generally like to make a bunch, all at the same time. The last time I did that, I burned 1/3 to 1/2 of the tank, running hard for a week.

 

So at a guess, that tank might hold me for a month to 6 months, depending on what I'm doing.

 

The reason that I had the big tank put in was to avoid schlepping the 100# tanks in and out of the truck. We have a 500 gallon tank that feeds the house, and I get them filled at the same time. I've never run out.

 

Geoff

Link to post
Share on other sites

Just for the record, I did the "just build one without putting too much thought into it" thing. I researched the crap out of burners, but for the forge itself I just made a simple box out of insulating fire brick (the soft stuff) with a frame of angle iron bolted together so that I could reconfigure the forge as necessary. Everything I've made in the last three years has been in that forge.

Link to post
Share on other sites

OK, so what is it that you don't like about that one?

 

G

 

Adam wasn't the OP. I think he was just throwing that out there as encouragement for "just going for it".

  • Like 1
Link to post
Share on other sites

 

Adam wasn't the OP. I think he was just throwing that out there as encouragement for "just going for it".

Exactly. :D

 

Though to answer the question for educational purposes, the big problem with my forge is uneven heating due to the geometry.

Link to post
Share on other sites

Brick forges have that problem, a round forge (as in built in a propane tank) distribute heat better. A ceramic wool forge is also easier to get an even heat on, it takes less to heat it and hold the heat better. Bricks are a terrible insulator, in comparison.

 

Geoff

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...