Simple Atmospheric Gas Forge Plans

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I have had a lot of people ask me if I have any step by step plans to build an atmospheric gas forge.  So, I decided to build a simple gas forge that can be built without using a welder or a cutting torch.  This forge can be built with just hand tools that most people will already have, the only thing that you might have to buy would be a 2" hole saw to drill the hole to install the burner holder.   I used a new 5 gallon metal bucket for the forge body that you can pick up new at a commercial paint store.

bucket for the gas forge body

The legs for the forge were made from two pieces of 1 1/2 " x 1/8" flat bar 25" long.  The first two bends were at 2" from each end and the second bend was at 6" from each end.  This size flat stock can easily be bent cold, it would help if you had a vise, but it is not necessary.  You can do it with the workbench and a pair of vise-grip pliers to hold it down or you can clamp it to a piece of angle iron and form the bends around it.  There are a lot of different ways that you could make the legs.   You can look around your shop and see what you have laying around.   However you decide to make your legs just make sure that the top of the forge doesn't exceed more than 13.5" in height so that three firebricks will cover the front.   Also keep in mind that most five gallon buckets have a slight taper from top to bottom, so both legs will not be the same.  You need to keep the front side of the bucket at a 90 degree angle to the bottom of the legs.

leg brackets for the gas forge body

The burner holder is made from a 1 1/2" standard black pipe nipple 4 1/2 " long and two 1 1/2" conduit lock rings.  I cut the threads off of mine to make it look a little better, but it is not necessary.  The pipe nipple and conduit lock rings can be found at any big name hardware store.  Using a #7 drill bit I drilled and then tapped the burner holder for three 1/4- 20 NC bolts that will hold the burner in.  The picture below is a close up of the burner holder after it has been drill and taped.

close up of burner holder before it was installed in trhe forge body

  Below are several pictures of the forge with the burner holder installed and with the leg brackets bolted on.  I bolted the legs onto the forge using 1/4- 20 x 3/4" hex  head cap screws. The burner holder was offset 2" off center from front to back because of the two inches of Durablanket that will be used in the back of the forge and 2 1/2" off top dead center.  The hole in the forge body for the burner holder was made by using a 2" hole saw in a cordless drill.  Be careful when drilling the hole, because you are not drilling a flat surface and the hole saw will want to grab when it starts to come through the steel. 
I have now built several more 5 gallon bucket forges since the original the only major thing that I have done is add a 2" x 1 1/2" rigid conduit reducing washers to both side of the forge body when installing the burner holder this helps strengthen the body a little more for the weight of the burner.  The picture on the left below shows a close up of the reducing washer.  These are available at the big box stores such as Lowes and Home Depot.


forge body with the leg brackets installed            side view of the forge in the building process          


The next picture below is of the forge body after it has been painted using Rustoleum High Heat spray paint. The Durablanket lining and fire brick bottom have also been installed.  I used 4 running feet of 1" Durablanket by 24" wide to line the forge.  I first cut two round disc from the Durablanket to form the back wall, then I installed two layers of 1" Durablanket blanket for the side walls. Then I used two 9" x 4 1/2" x 3/4" heavy duty fire bricks for the forge floor, you will have to cut one of the bricks to length.  I cut my fire brick using a metal chop saw, you could also use a 4 1/2" angle grinder with a thin cut wheel.  If you do not have access to either one of these, they can also be cut using a hand chisel.  Score the brick all the away around and continue slowly cutting it the rest of the way through.  When working with the ceramic blanket and cutting the fire bricks always wear the proper respiratory protection.

forge body with firebrick floor installed

The next picture below is of the finished gas forge with the firebrick front and side arm burner assembly installed. When installing burner assembly in the forge
the flare should not extend down into the forge chamber it should be up inside the Durablanket about a 1" to help protect the flare from the high heat in the forge chamber.  The inside of the forge has also been coated with 2 pounds of Plistix 900F coating. The Plistix 900F coating helps to improve the efficiency of the forge and it also prevents fiber floating from the ceramic blanket.  I did not coat the front edge of the ceramic blanket with the Plistix coating, this will give the blanket a soft edge that will help seal the front with the firebricks. The firebrick front is definitely not the most efficient way to close up the front of the forge, but it is very adaptable to many different opening configurations.  It is also a very cheap and quick way to close up the front opening.  The opening in the forge is 4.5" x 4.5", but like I said you can configure the opening to suit the work that you are doing at the time.  In the picture you can also see that I packed the area between the burner holder and the burner tube with scrap Durablanket, this will help seal off this area a little better and prevent the heat from coming up around the burner tube.

    forge complete with firebrick front installed         


The picture below is of the forge with the side arm burner running at 7.5 psi, the forge has been up and running for about twelve minutes.  The 1 1/4" x 1/4" piece of mild steel has been inside the forge for about 4 minutes when this picture was taken.

this is a side view of the forge running           

The picture below is a close-up of the inside of the forge with the burner running at 7.5 psi. This close up also gives you a good view of the Plistix 900F coating installed over the Durablanket ceramic blanket.

this is a close-up view of the inside of the forge with the sidearm buner lit

Please visit my frequently asked questions page it contains more useful information about building gas forges and atmospheric gas burners.   Please check this page out, there is a wealth of information there.  There is a parts list below that contains all of the parts and quantities used to build this forge.  If there are any questions that I left unanswered about building this forge, please let me know so that I can help you with them.   I would also greatly appreciate your comments and suggestions about these forge building plans.   My e-mail address is below.


Update: January 12, 2006: Today I measured the temperature inside the forge using an Omega HH300 Series Digital Thermometer and # KHXL-14U-RSC-12 thermocouple, these items are both available from omega.com.  The forge had been up and running for fifteen minutes with the propane regulator set at 7 psi and the temperature reading inside the forge was 2120 º F.  I am using a 16" x 30" steel service cart ( Lot No. 5107 ) that I bought from Harbor Freight for my forge cart, they can be bought for $23.00 on sale.  This is a lot easier than trying to round up all of the materials and building your own cart.

Update: February 2. 2006:  Today I measured the temperature inside the forge using an Omega HH300 Series Digital Thermometer.  The forge had been up and running for fifteen minutes with the propane regulator set at 15 psi and the temperature reading inside the forge was 2250 º F.

Update:  March 11, 2006  I found a source for 2600°F insulated firebricks, so I replaced the heavy-duty firebricks that I was using for the front of the forge with insulated firebricks.  This should help to improve the performance of the forge.

Update:  November 4, 2006  The total inside volume of this forge is approximately 460 cubic inches, so it would be marginal at best in achieving forge welding temperatures.  The rule of thumb for side arm burners to forge volume is: (1) 3/4" side arm burner for every 350 cu/in of interior forge space if you are wanting to achieve forge welding temperatures. Note: these figures are for a properly insulated forge.  I have talked to several knifemakers who have built this forge with two burners instead of one to insure that they can achieve forge welding temperatures and they are very happy with the results.

Update:   March 10, 2009  The biggest problem that I had with the simple gas forge was that the back of the forge was closed up. Therefore, one could not heat the center of a long piece of stock.  Other people have made comments about the gas forge as well, they suggested that it includes a hole in the back.  I initially suggested simply drilling a hole in the back and plugging it with a piece of Durablanket when you were not using it.   Still, I wanted to come up with a better method other than just drilling a hole in the sheet metal that would probably burn up in no time.  Then, I came up with the idea of using the same door that NC Tool uses on their gas forges.  They have one that is just a hole that you can pass the bar through and the other had a flap door that will close when not in use.  I purchased several of them from NC Tool and installed one on the last simple gas forge that I built.  Below are some pictures of the forge with the door and some notes on the process of installing the door.  You could use this same set up on a Freon bottle forge, air tank forge, Propane bottle forge or a fabricated sheet metal body forge as well.
 

            

The first picture above is of the two different openings that are available from NC Tool.
( note: the one with the fixed opening is called a cast iron sleeve and the one with the door is called a cast iron sleeve with flap if you wanting to order one from NC Tool. )  The second picture is of  the back of the forge body with the 3 3/4"wide  x 2 1/4" tall hole cut into the center of the forge body .  Once you have the hole cut in the back of the forge cut and the holes drilled you can install the two layers of 1" Durablanket that you are using for your forge back and then cut the hole in the Durablanket the same size as the hole that you cut and the door fitting will slide right in. (Note: I use an old kitchen paring knife to cut the opening in the the Durablanket )


                   

These pictures are of the back of the forge with the door installed with the sheet metal screws that come with the sleeve and one picture shows the door with a piece of stock sticking through.






Forge Parts List:

(1) 5 gallon metal bucket
(2) 1 1/2 " x 1/8" flat bar 25" long or similar
(7) 1/4-20 x 3/4" NC hex head caps screws  ( 3 for the burner holder and 4 to bolt the legs to the forge body )
(7) 1/4-20 hex nuts ( 3 for the burner holder and 4 to bolt the legs to the forge body )
(4) 1/4" flat washers
(4) 1/4" lock nuts
(1) 1 1/2" x 4" schedule 40 black pipe nipple
(2) 1 1/2" conduit lock rings
(2)  2" x 1 1/2" rigid conduit reducing washers
( 4 running feet) 1"  8# density 2300°F Durablanket 24" wide
(1) 3/4" Side arm burner or (1) Z Burner
(2) 9" x 4 1/2" x 3/4"  3000°F heavy duty fire bricks ( for the forge floor )
(6) 2 1/2" x 9" x 4 1/2"  2600°F insulated firebricks ( to make the front of the forge)
(2 Pounds) Plistix 900F
(1) cast iron sleeve or cast iron sleeve with flap. (to make the rear port opening or rear door )

Below is a list of parts that you will need to get from the propane tank to the burner gas inlet. (Note: all of the following parts listed below are contained in the single burner connection kit. )

(1) 1/4" MPT x full flow  Hard Nose POL 7/8 hex
(1) 1/4" X 1/4" FPT 3-35 lb Propane Regulator Model
(1) 0 - 30 PSI Gauge bottom connect with 1/4" mpttt
(1) propane hose with 1/4" male pipe threads on both ends
(1) 1/4" N.P.T. ball valve
(1) 1/4" x 1/8" threaded black iron pipe bushing




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Zoeller Forge specifically disclaim any responsibility or liability for damages or injuries as a result of any construction, design, use or application of information contained on this web site.

Please send your comments or suggestions to : zman59@earthlink.net

Copyright ©2006 - 2012 Larry Zoeller

Last Revision 10/29/12






 
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