Forge Question

Discussion in 'Hot Metal' started by rezz, Jul 4, 2017.

  1. rezz

    rezz Member

    I'm in the process of building a forge and need some info.

    My plan is to use 2 stainless steel containers, one is 10" diameter and the other is 7".

    I intend to put the smaller one inside the larger one and put insulation around the outside of the inner container. Is there anything wrong with doing it this way??

    The inner container would be the actual burn chamber with stainless walls that have insulation on the outside. This would leave bare SS inside the forge and exposed to the burner.

    Will it work??
  2. EdCaffreyMS

    EdCaffreyMS Forum Owner - Moderator

    It will work....but it will be grossly inefficient, and unless the burner(s) you use are absolutely huge, the heat you achieve will be limited. What will happen is that the thermal mass of the interior "container" will have to be heated before the the insulation starts doing it's job. You'll also have the issue of the inner "container" being eroded by the burner.... and the heating/cooling.

    Personally, I would say that he "cons" of this design far outweigh the "pros".
  3. Mark Knapp

    Mark Knapp Dealer - Purveyor

    I agree with Ed, The inside liner will not hold up. Best to stick to the conventional method.
  4. rezz

    rezz Member

    Okay, scrap that idea. Should have known since I haven't seen anything like that anywhere. I got the idea because some forges have a round pipe inside and .................oh well.

    The insulation should be here tomorrow and I have some castable cement to coat that with. Now I'm debating on putting some firebrick inside for a floor but will study on it after the insulation is in.
  5. EdCaffreyMS

    EdCaffreyMS Forum Owner - Moderator

    Horizontal or vertical forge? If horizontal, put your insulation in (I assume you're using ceramic fiber), with the ends butting up on the bottom. When you "coat" the insulation, don't over do it! Thin what you're using down to about the consistency of latex paint, spritz the ceramic fiber with water, then use an old or cheap paint brush to apply a THIN coat. LET IT CURE NATURALLY/ COMPLETELY. Depending on where you are, and the weather, that can take a week to a month or more. DO NOT try to cure the coating by firing the forge.... it'll just crack and fall off soon afterward if you do.

    Get yourself a "1/2" firebrick (a firebrick that is the size that you would get if you took a standard size firebrick and split in half's the same size as a standard firebrick, but only 1/2 the thickness). Use that as the "floor". Just put it over where the ceramic fiber butts up to itself, and nestle it down a bit. You can even use a little refractory cement to soften the edges of the brick so the burner flame is smoother when it crosses that junction.

    When you build a forge, the hardest part is having the patience to let anything "wet" cure..... if you don't, you're gona be doing it over in a very short time. If you let it cure out fully, it will last MUCH longer.
  6. rezz

    rezz Member

    A MONTH?? Ain't no way I'll be able to wait a month for that stuff to set 'properly'. :D

    I do have some of that firebrick you are talking about after finding it locally today. There were 6 in the box @ 9" x 4.5" x 1.25" and its made by Rutland. So it will definitely be in the bottom.

    This is to be a horizontal forge and the primary use will be HT.....but I may end up trying some actual forging with scrap metal and/or railroad spikes. Not really interested in that but may try it.

    I've ordered a burner that should be here next week at least. It is this one:
    [​IMG] [​IMG][​IMG]
    Goede G-2 stainless steel forge/foundry burner with 0-30 PSI regulator and 0-60 pressure gauge.
    • Heavy duty stainless steel construction.
    • 130,000 BTU rating at 30 PSI pressure
    • Adjustable air choke and expansion chamber
    • The end of the burner measures 1-3/8" to fit 1-1/2" forge/foundry opening.
    • Pressure gauge to measure gas flow

    It sounds pretty good and if it does what it says should do most of what I'm wanting to do.

    Thanks for your help and advice. I'll post more of the build as it progress in case anyone is interested.

  7. EdCaffreyMS

    EdCaffreyMS Forum Owner - Moderator

    "A MONTH?? Ain't no way I'll be able to wait a month for that stuff to set 'properly'. :D"

    That's the feeling we all included, but after you trash a couple of forges, and have to plunk the $$$ into the same forge again, your patience will grow. :)
    Last edited: Jul 6, 2017
    Smallshop likes this.
  8. rezz

    rezz Member

    I scrapped the original idea of the stainless steel pot and got an air tank. Here's what I've got so far:



  9. WY_Not

    WY_Not Well-Known Member

    Others would certainly know better than I, but... would it be better to place the "seam" in the wool under the brick? Or does that become irrelevant once the refractory is applied?

    @Wayne Coe ?
    rezz likes this.
  10. EdCaffreyMS

    EdCaffreyMS Forum Owner - Moderator

    You'll wanna put the "seam" of the ceramic fiber (where the two ends butt together) UNDER the firebrick.... if you leave it as is, the flame from the burner will quickly erode it along that "seam". I would also recommend a different placement of the burner..... centered in the forge body, and angled like this....

    You don't want the flame from the burner to be in any position to directly contact/impact the work piece.....and you'll much more even heating if you can create a "swirl" such as....

  11. rezz

    rezz Member

    Thanks all. Its looking a bit better. :confused:

    I remembered about putting the seam on the bottom but that pic is just a temporary test for fit. I'll rotate it around before applying the coating.

    Burner placement....some people recommended putting the burner at the front or back 1/3 of the tank and angling it so the flame would hit the wall and swirl like you said. I understand not to blast the blade directly with the flame and think there's enough play in the burner pipe to allow some adjustment.

    Ed, On your pic the front is completely open. Do you block it off at all or use it like that?

    I've got another roll of insulation which would put it at 2" thick. Would that be overkill?

    Here's a pic of the first attempt at knife making using stock removal. It's pretty rough but not too bad:
    Last edited: Jul 6, 2017
  12. rezz

    rezz Member

    Thanks're right. Will fix it before applying cement
  13. EdCaffreyMS

    EdCaffreyMS Forum Owner - Moderator

    "Ed, On your pic the front is completely open. Do you block it off at all or use it like that?"

    Oh yes! I have firebrick to close down the front to just big enough to accommodate whatever I'm working on.

    I know there are some who advocate burner placement like that, and I did try it, but quickly went back to centering the burner because which ever way that burner holder is directed (forward or rearward), that particular area gets really hot, and the rest of the forge is cool by comparison. Give it a shot since it's already there, and if it ain't broke....don't "fix" it. :)

    A couple of things to be aware of...try to steer clear of that galvanized stuff when it comes to forging and/or forge parts.....when galvanizing burns (and it will), it creates poison gas. When you fire that forge up, do it somewhere open, and let it run until the paint on the outside burns off...that's nasty stuff too!
  14. WY_Not

    WY_Not Well-Known Member

  15. Dennis Morland

    Dennis Morland KNIFE MAKER

  16. WY_Not

    WY_Not Well-Known Member

    Doh! Didn't even think about that one. And that is the site I used to pattern my firebrick forge. :(
  17. rezz

    rezz Member

    Thanks everyone.

    I got it going pretty well and have been able to easily get blades to temp for HT. It has also been good so far for forging and I was able to make some 'functional' tongs out of 1/2" round bar.

    I put a fire brick standing on edge opposite the burner and that helps with the swirl and there is a good area of high heat along side that brick and toward the back.

    It could stand some tuning but so far its good for me when running at 12 psi gas. There was 6 knives in various stages of completion and they have now been HTed and finished and given to the lucky recipients. They turned out pretty well for an amateur and the last 2 were were better than the others. I have about got the handles down pretty well but the blade finishes are pretty rough but they will definitely cut. The mirror finish is not really what I want anyway and the first knife made got a dose of hot sauce for a patina which looks pretty good to me.

    I will work with the forge some more and adjust it some while making a few more tongs and whatnots to get used to the work and get some of the bugs out of me and the railroad anvil creation that has been made. Here's a couple of pics of it in action with some files inside:


  18. latticino

    latticino New Member

    I built one of my gas forges out of a similar Harbor Freight air cylinder (11 gallon size I think). Cut about 6" of length out and it still is kind of large. Looks like you are using full thickness fire brick in your forge, which is a lot of thermal mass and will heat slowly. Consider replacing those with 1/2 bricks like Ed suggests above. Your door openings are a bit large for efficient use as well. Hopefully you block them off in use.

    In the last picture your forge appears to be running very cold. Hopefully this shot was just to illustrate the burner flame, not to show the forge at working temperature.

    For what it is worth, the longer the stock sits in the forge up at forging temperatures the more scale loss and surface decarburization you will get. My suggestion is to keep only the stock you are actively working on in the forge (or staging to get up to temperature while working multiple pieces simultaneously).

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