Ed Are you still using salt tanks?

Discussion in 'Ed Caffrey, MS "The Montana Bladesmith"' started by Diamond G Knives, May 15, 2011.

  1. Diamond G Knives

    Diamond G Knives Well-Known Member

    Just trying to put some thought into the new shop and was wondering if you were still using salt tanks. This has always sounded like a very finate way to hit HT temps and lower cleanup time with lack of scale.

    Just wondering if you were still using them, and what your opinion was on them. Any tips and insight would be appreciated!

    Also doeas anyone have plans for setting up a gas fired Salt pot? What do I need to start collecting??

    God Bless
  2. Wayne Coe

    Wayne Coe Forum Owner - Moderator

  3. EdCaffreyMS

    EdCaffreyMS Forum Owner - Moderator

    Hi Mike!

    Yes, I still use a salt tank. Compared to other methods, it provides super fine accuracy/consistency.

    I think a gas fired setup is the only way to go with Salt Tanks.

    Essentially all you do is built a vertical forge, and use a Stainless tank (I prefer 300 series SS for the tank), a PID controller, thermocouple, a normally closed magnetic gas valve, and enough propane plumbing to fit your needs. I use a single venturi burner, located at the bottom of the forge.
    The biggest "trick" in getting accuracy out of a salt tank is the size of the actual salt container used. You have to realize/remember that the salt is "thermal mass"....that means that the smaller you can keep the diameter of the tank, the less temp swing you will realize.
    For example, the tank I use is 2 1/2" ID X 3/8" wall X 20" long. My tank will hold within 10-12 degrees of the set point. Use a tank that will just accommodate the largers blade(s) you ever thing you will make.
    I have had folks call and ask me to help them with salt tanks....one person that comes to mind insisted that he was going to use a 6" ID tank. I tried to talk him out of it, telling him that he would get massive temp swing with that much thermal mass heatting up and cooling down all the time...but he went ahead and did it anyway. About three months later he called me again, all upset that his setup was giving him temp swings of 100-200 degrees. (He was using the 6" tank). He could not understand what I was trying to tell him about the thermal mass that much salts put into the equation. I finally told him that his salt tank would never "even out" until he went smaller. To this day I have no idea if he ever tried a smaller tank.....I suspect not, because I saw a classified on one of the forums from him, offering "salt tank parts".
    Don't think there is NO cleanup, there is, it's just a lot easier clean up than having scale to work on.
    If you take the time and effort to think through a salt tank design, and use it cautiously, it can be a very effective and useful addition to a knifemakers shop.
  4. HHH Knives

    HHH Knives Super Moderator

    Morning Ed, I wonder if you would explain the reason you use a salt tank.. I mean I dont understand the process or what it does.. What part of the HT does it replace..

    Always interested in learning.. and your posts and info is always very informative. Thanks in advance for your time.

  5. cdent

    cdent Well-Known Member

    I hope it's ok to mention here that there's a sticky up at the top on bladeforums that gives a rundown on salt pots. I've been lucky enough to take a peak at Ed's setup, couldn't be simpler in a good way.

    Take care, Craig
  6. EdCaffreyMS

    EdCaffreyMS Forum Owner - Moderator


    The salt tank is about about control. You can precisely control temps. Because you are heating in a liquid, through conduction, rather than convection as in a forge or with a torch, it offers a level of control that just isn't possible when heating through convection. Because the hot steel isn't exposed to the atmosphere, there is almost no scale to deal with during cleanup. Because the salt tanks are so precise, you can take a blade very close to finished, heat treat it, and have minimal cleanup when it's done....that equals a lot of time savings.
  7. Diamond G Knives

    Diamond G Knives Well-Known Member

    Are you using 2 tanks? One with high temp salts for HT and one with lower temp salts for Tempering?
  8. EdCaffreyMS

    EdCaffreyMS Forum Owner - Moderator

    I rarely use low temp salts, but when I do, I simply use my tank of Nirte Blue.......that way I can get "double duty" out of one product. (low temp "salts" as well as bluing capability)
  9. UncleBillyKnives

    UncleBillyKnives Well-Known Member

    Ed, I have a question, how does the tank sit in the vertical forge? is there space between the tank and the insulation that allows the heat to flow aroung the SS tank? thank you in advance.
  10. EdCaffreyMS

    EdCaffreyMS Forum Owner - Moderator

    Yes. The vertical forge body is 12"ID, with 1" of kawool coated with ITC......so the actual ID of the finished "forge" is 10", and my tank that holds the "salts" has a 2 3/4" OD.......that means there is approx. 7 1/4 inches of air space between the ID of the forge, and the OD of the salt tank. The forge actually has a "lid" with a "chimney" on it to direct the hot exhaust away from me, and the hold the top of the tank centered in the forge. You can see pics of it on this page: http://www.caffreyknives.net/bsteel.htm
  11. UncleBillyKnives

    UncleBillyKnives Well-Known Member

    Thanks Ed. I was talking to the guys in the fab shop where I work about the use of a salt pot. Of course they got excited and want to know when we start.. I am always nervous about new thing like this, but they already found a piece of 2" SS pipe 1/4" wall thinkness. I am not sure of the grade of SS.

    Can you do most steels with this type of set up? I typically use 0-1, A-2, 1095, and one ELMAX. I also have a couple pieces of 1080 or 1060 i was saving to forge with.

    Again, thanks for the posts. I really enjoy them.

Share This Page