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Thread: WIP Gas forge

  1. #1
    Join Date
    Jun 2013
    Location
    South Otago New Zealand
    Posts
    66

    WIP Gas forge

    I got another batch of knives heat treated today and it reinforced the notion that I needed a better way to do it than in the kitchen fire. I had been looking at gas forges for a couple of weeks and decided to build one for myself. There are a couple of good videos of how to make them from the 20lb gas bottles so when I was in the city yesterday I went to the metal scrap yard but the only gas bottle on the yard, had the top cut off it but there was a stack of lazer cut 10 3/4 in dia x 3/16 discs there so I got two of them as well as a length of 1 inch black pipe for legs.
    This is the bits I bought home.

    So the first job was to grind the opening out a little to fit the plate which was a simple mark and grind.

    I decided to do the bottom as well because when they were doing them on the youtube it seemed like a bit of a chore to make the insulation conform to the semi rounded shape so I figured that a flat surface woudl be easier.



    Von Gruff

    The ability to do comes with doing.

    Love is Genesis 12: 3. Exodus 20: 1-17. Acts 4: 10-12

  2. #2
    Join Date
    Jun 2013
    Location
    South Otago New Zealand
    Posts
    66
    Then it needed a little clean up to make sure the plate fitted nice and flat. A friend just down the road welded the plates in place for me, so that all needed a clean up. I gave it all a good going over with a heavy flapper disc on the grinder to get rid of the old paint and the bit of surface rust.

    I set it up with a couple of blocks to hold it still and make sure it was more or less secure for the marking out of the next step. Having the flat plate on the ends made this easier so I was pleased that I hadn't started with a complete bottle for a start as I might have had to do it on the curve surface.
    Finding the center of the plate both verticall and horozontally was a simple matter, so after leveling the line accross the front (and rear as well) I was able to do the vertical which allowed me to mark the top center mark where the handle will go.

    I have seen various measurements for the offset of the gas inlet from 10degrees to 30 and as the idea is to make the gas swirl round the inside of the forge I went with 25 degrees. Marking a square on the board and a 25 degree line in, I could go up the line by haf the dia of the bottle and get the measurement away from the center line that would give me a 25 degree offset.

    So that can be marked on the top of the bottle ready to be drilled for the gas inlet.

    That is where it will have to sit till the gas bits and the insulation get here in a few days. I will need to get the exact height of the insulation plus the fire brik floor before I cut the opening at each end.
    Von Gruff

    The ability to do comes with doing.

    Love is Genesis 12: 3. Exodus 20: 1-17. Acts 4: 10-12

  3. #3
    Join Date
    Sep 2009
    Location
    Great Falls, Montana, USA
    Posts
    2,741
    I would encourage you to NOT close up the back end of the forge in that manner (tightly sealed). Propane forges will operate better, and be far easier to adjust/control if they can "breathe". Stacked firebrick at the rear (and front) allows the forge to breathe, reduces the "dragon's breath" you'll get out of the front opening, and gives you increased versatility in that you can easily "open" be back for longer items to "pass through", as well as adjust the front opening to your needs.

    Not sure if the following will make sense to everyone, but the reality of a propane forge is that it's essentially nothing more then a controlled explosion. Tightly enclosing a forge greatly increases the chances of mishaps by turning a flammable gas into a compressed flammable gas..... not a good scenario.
    Last edited by EdCaffreyMS; 03-14-2017 at 10:44 AM.

    www.caffreyknives.net
    Caffreyknives@Gmail.com

    "Nobody cares what you know.....until they know you care."
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  4. #4
    Join Date
    Jun 2013
    Location
    South Otago New Zealand
    Posts
    66
    I had a busy day in the shed with the forge up to as far as I can take it untill the insulation gets here and then I got the bolsters on two of the knives I am doing and the handes on the third.
    This is the stage the forge is up to now and you will see that I took the advice and opened a port in the rear as well.
    https://www.youtube.com/watch?v=zDfe...ature=youtu.be
    Von Gruff

    The ability to do comes with doing.

    Love is Genesis 12: 3. Exodus 20: 1-17. Acts 4: 10-12

  5. #5
    Join Date
    Jun 2013
    Location
    South Otago New Zealand
    Posts
    66
    Made some progress on the forge yesterday and the first thing I needed to do was to get a hole through for the gas supply. I read some more on the angel of delivery and ended up going with the full 30 degree offset. So lots of 1/8 in holes round the perimeter

    Some time with a good 1/2 round file, the insulation in and away down to the garrage to get the the end welded on and the outer gas delivery pipe welded in

    The venturi system has a nice air supply regulator with it fully open here for full heat forging. I saw a video with this gas system and he reached welding heat in 2 1/2 minutes

    And closed right down. For the heat treating the air supply is closed down quite a bit to controll the temperature
    Von Gruff

    The ability to do comes with doing.

    Love is Genesis 12: 3. Exodus 20: 1-17. Acts 4: 10-12

  6. #6
    Join Date
    Jun 2013
    Location
    South Otago New Zealand
    Posts
    66
    The fire brick was placed in and settled down into the insulation

    The rigidiser was sprayed onto all the insulation, the refractory cement was mixed and laid into place

    Now I have to wait a few days for it all to dry before it gets a firing

    In the meantime I had a look at the piece of a press die I got from the scrap yard the other day. It is a ft and a bit long x 4 3/4 x 2 with the bottom very neatly radiused

    I decided it is a bit long for what it may turn into so I have marked it out to be cut back to 8 inches and will look for a piece of 4x4x8 steel and a piece of 2 or 3 in round stock when I am down to the city again next week. It is all going to be reconfigured into an anvil for a bit of steel pounding which almost certainly means that some work will be done on it with hot steel and a hammer.
    Von Gruff

    The ability to do comes with doing.

    Love is Genesis 12: 3. Exodus 20: 1-17. Acts 4: 10-12

  7. #7
    Join Date
    Jun 2013
    Location
    South Otago New Zealand
    Posts
    66
    I got the forge finished but had trouble getting anything like a usable burn going and after some consultation it seems I have the wrong regulator so the correct one is on the way. I should be able to get it fired up and working propperly by early next week but in the meantime this is a video I did of it at this stage and the anvil I have been making.

    https://www.youtube.com/watch?v=zNiz...ature=youtu.be
    Von Gruff

    The ability to do comes with doing.

    Love is Genesis 12: 3. Exodus 20: 1-17. Acts 4: 10-12

  8. #8
    Join Date
    Jun 2013
    Location
    South Otago New Zealand
    Posts
    66
    I was talking to the supply outfit about the regulator (and to order another 8 ft of blade stock) and it should be here in the morning so the forge can get its first heat up. I had a batch of knives ground up so gave then a hand sand to 360 to be ready for the heat treat which I cant do for a couple of days as I have been helping a friend to shift house (to a town an hour away) so it wont be untill I get that sorted out that I can get back to the shed.


    A boner, general hunter, 3 hunter skinners and a wapiti hunter. One of the hunter skinners and the boner are for me. I have a field scalpel and a light hunter (for myself) away being heat treated as it is in a SS (N690) which I cant do with my equipment.


    Von Gruff

    The ability to do comes with doing.

    Love is Genesis 12: 3. Exodus 20: 1-17. Acts 4: 10-12

  9. #9
    Join Date
    Jun 2013
    Location
    South Otago New Zealand
    Posts
    66
    Things came together this morning when the regulator arrived and I could get back to the shed. It didn't take long to get things assembled and the forge fired up. I had an old pick that I will never use again so I cut one of the pick arms off so it would fit in the forge to see how long it would take to get to red heat. I turned the vodeo off just before it reached the heat as it is a bit boring but from cold it took about 7 minutes to get to heat so I plunged it into the oil quench tank to bring the oil to temp for quenching the blades I was about to heat treat.
    6 minutes of watching it heat up but for me it was interesting so this is the video
    https://www.youtube.com/watch?v=1cli...ature=youtu.be
    Von Gruff

    The ability to do comes with doing.

    Love is Genesis 12: 3. Exodus 20: 1-17. Acts 4: 10-12

  10. #10
    Join Date
    Jun 2013
    Location
    South Otago New Zealand
    Posts
    66
    I had ground another two boning knifes yesterday as I had another order for one and thought to get one ahead for a stock blade that I would just have to put a handle on when needed.
    I was very surprised to find just how quick it was to heat treat the blades in the forge with 8 being done in about as many minutes.
    I had ground another two boning knifes yesterday as I had another order for one and thought to get one ahead for a stock blade that I would just have to put a handle on when needed.
    I was very surprised to find just how quick it was to heat treat the blades in the forge with 8 being done in about as many minutes.
    https://www.youtube.com/watch?v=puwv...ature=youtu.be
    This was the blades after heat treating anf tempering
    Von Gruff

    The ability to do comes with doing.

    Love is Genesis 12: 3. Exodus 20: 1-17. Acts 4: 10-12

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