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Thread: Forge or furnace

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    Forge or furnace

    Hi guys

    I am new to knife making and just trying to set up my work area.

    I am not sure whether I should get a forge or a heat treating furnace? My understanding is that a forge will be a lot cheaper to buy, but I am not sure how do you actually know what the temp is and how do you ensure that you not over or under heat the blade? Do you go by colour alone? Can be a bit daunting for an inexperienced newcomer..

    It is my understanding that with a furnace you can control the heat and ensure that you get more or less the correct hardness. But can you heat metal in a furnace to a high enough temperature to forge/hammer it?

    Any advice will be greatly appreciated!

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    Australian Knifemakers Guild
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    A furnace is really handy for heat treating stainless steels but very expensive to buy.
    If you are just starting out just buy or make a forge and stick to carbon steels that are easy to heat treat. It is a bit difficult using a furnace for forging.

    You can buy great value gas forge parts from Artisan Supplies but a furnace will set you back at least $2000.

    Before you become too confused by all the amazing machinery out there, see if you can lay your hands on some of the great textbooks out there. I would highly recommend 'The Complete Bladesmith' by Jim Hrisoulas. I have had it for years and refer back to all the time.

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    Hi Jez

    Thank you very much for the reply and advice! I have just ordered the book from Amazon

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    You'll find that book on the shelves of most bladesmiths in the country. It's full of heaps of sensible, technical information.
    I was looking at it last night for lost wax casting information.

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    More Posts Than the Rabbit Proof Fence ndp_2010's Avatar
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    I think a gas forge is a great investment into knifemaking, firstly its good for heat treating carbon steel but also great for forging steel later if thats what you want to to.
    A 9kg gas forge will heat treat a blade 8-9 inches long maybe 10 inch if you can deal with a little bit of heat difference along the blade.
    There plenty of info on building them on this website and materials are readily available in kits.

    I have also succesfully heat treated longer blades in my 9kg forge, latest was a 20 inch long short sword. I was using 1070 so there was a bigger temperature window for hardening, but keeping the blade between in the range of 820-30C was not too difficult with some practise.
    Another benfit of a gas forge is that when you heat treat you can reduce decarb from oxidation (compared to a furnace which is a high oxygen environment).


    I also have a heat treating oven/furance. Yes it is nice to be able to control temperature and have the heat in an enclosed space, however, you get much more decarb on carbon steel blades, as you need to harden without foil wrap for oil quench. Heat treating ovens are also expensive, and more likely to have uneven temperature inside them (as there is little to no air movement compared to a forge where gases are flowing all the time). In my case I bought a heat treating oven from paragon and the temperature is 50 degrees hotter in the back compared to the probe. I am told the newer ovens have less difference but it is something to consider.
    I have used my oven to HT stainless steel as well, having controlled temperatures to 1080C is nice, and being foil wrapped no issue of decarb.

    My advice would be build a gas forge and see how you go, the layout is less, and IMO more versatile. If you do end up wanting to more stainless blades I would then invest in an oven. just my 2c.


    specifically to answer your question, a furnace is not practical to use as a forge, once you open the door and put cold steel back inside it takes alot longer to heat up compared to a gas forge thats burning at maximum flow.
    2nd, a gas forge can be controlled quite well for temperature I have found, in the 800-850C range. I have not tried to keep a controlled temp at high temperatures (for stainless) but maybe someone can let you know.
    Last edited by ndp_2010; 02-03-2017 at 18:10.

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    Hi

    Thank you so much for your comprehensive reply!

    At this stage I will definitely follow your advice and go with the 9kg gas forge.

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    Gas forges are definitely the go. I have 3 and I love them all.
    They are fast, efficient and cheap.

    I also have a Paragon furnace which I use for a lot of interesting processes - but not forging.

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    Thanks Jez, I appreciate the input!

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