WIP Gas forge

Discussion in 'Knife Dogs Main Forum' started by Von Gruff, Mar 13, 2017.

  1. Von Gruff

    Von Gruff Well-Known Member

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

    Von Gruff Well-Known Member

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

    EdCaffreyMS Forum Owner - Moderator

    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: Mar 14, 2017
  4. Von Gruff

    Von Gruff Well-Known Member

    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=zDfeiwCa5c0&feature=youtu.be
     
  5. Von Gruff

    Von Gruff Well-Known Member

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

    Von Gruff Well-Known Member

    The fire brick was placed in and settled down into the insulation
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    The rigidiser was sprayed onto all the insulation, the refractory cement was mixed and laid into place
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    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
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    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.
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  7. Von Gruff

    Von Gruff Well-Known Member

    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=zNizltSvmQk&feature=youtu.be
     
  8. Von Gruff

    Von Gruff Well-Known Member

    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.


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  9. Von Gruff

    Von Gruff Well-Known Member

    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=1cliTeG5sRA&feature=youtu.be
     
  10. Von Gruff

    Von Gruff Well-Known Member

    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=puwvvs5_IN8&feature=youtu.be
    This was the blades after heat treating anf tempering
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  11. Von Gruff

    Von Gruff Well-Known Member

    I have these knives uo to the stage where the handles are having the finish applied so today I started on the sheaths.
    I got in a new double shoulder of 3mm (1/8) cowhide so marked out the patterns with as little waste as possible.
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    I had a little lefy from the previous piece so made up a couple to make sure my new patterns were fitting the knives propperly and then cut out the rest.
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    With the belt loops sewn in and the welt glued in I will leave them till the adjustable U groover gets here to make the turn over of the back to the front much easier. A friend showed me his and how he runs a couple of grooves down the inside of the sheath either side of the center line and the leather folds over and lies much flatter for punching the stitch holes.
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    Before I started this morning I made a third hand to make the stitching much easier and when I stitched u the couple of trial sheaths I was quite impressed with how much easier it is compared to how I had been doing it for the last near 50 years.
     
  12. Von Gruff

    Von Gruff Well-Known Member

    So this is the knives as they stand at the moment. They still have to have the final blade finish and be sharpened.
    First are some hunter skinners and this first one with cocobolo scales I was going to keep for myself, but will probably sell it on as I have some lovely wood coming from the US, thanks again to Frank who has made much of this possible by sourcing and shipping various goodies for me.
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    walnut and ebony
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    walnut and jarah
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    A wapiti hunter in walnut and hickory
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    Last edited: Apr 21, 2017
  13. Von Gruff

    Von Gruff Well-Known Member

    and a few boners
    First is a special order companion knife to go with a light hunter in the same walnut and jarah shipped of a short while back
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    One for myself in a specail piece of walnut cut from my late fathers yard in the early 80's
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    And a plain walnut one just to start getting one or two ahead for casual sales.
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    I seem to have missed getting a pic of a general hunter in walnut and jarah but it is on the bench anyway and as ready as these are.
    In this pic of them in the sheaths thata still have to be hot wax dipped there is three extra that are still to be finished. On the far left is my own personal light hunter in a fantastic piece of olivewood and buffalo horn that I will show propperly when it is finished with the top left being a new killing knife (for the sheep) with walnut and copper pins, and a little field scalpel with buffaol horn scales.
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    Last edited: Apr 21, 2017
  14. Smallshop

    Smallshop KNIFE MAKER

    Nice Job...love those sheaths.
     
  15. Von Gruff

    Von Gruff Well-Known Member

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