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jhobson

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  1. Re-reading... I would guess that a horizontal quench could increase warping for a fencing blade. Vertical oven would be the way to go but initially the 'tank' can be thick wall steel pipe - just make sure to empty it of salt and check it after each use.
  2. For just starting out experimenting, I think this can be really low tech. The salts are good for: quick quench, thermal mass, reduce oxidisation. I think you can get all these benefits by having a small trough inside an oven... get it up to heat, then quickly open the door and drop the blade into the trough, slam the door shut. For a one-off, I would guess any iron/steel trough would do. You probably only need thick stainless if you are doing this repeatedly. However, I am guessing so do this on a non-organic floor! I have proper 20kg of salt I (well, Owen) bought 10 years ago and I'm still waiting to use them. Back then, it seemed difficult to get nitrate salts in quantity because they make good weapons. Now it seems much easier to buy potassium nitrate (which i think is a key low-temp salt - melting point 334° C so needs mixing with some other salt (mixtures are always lower melting point - something to do with entropy :) )) in reasonable bulk. So take a look at the salt recipes... used to be here https://www.bladesmithsforum.com/index.php?/topic/6375-heat-treating-salt-recipies/&page=2 but all links seem broken. I'd love to see that document again :(
  3. Why would low temp salts would be more dangerous than molten lead? I think low temp salts are a faster quench than lead so you have more time to 'avoid the nose'. Low temp salts would be handy for doing 'Blueing' as well which you might find a use for... and it is easy. Where do you think the extra cost is?
  4. I forgot to confirm - it is very effective at damping the vibrations.
  5. I'm probably not the first to suggest this - sorry if it is a repeat... This stuff is like Plasticine when the packet is first opened, then dries to a soft plastic/ hard rubber consistency I just used it on my brass handled dagger. Even with the pommel nut tight, when you knock the tip you would get an unpleasant vibration. So I tried this stuff to: Rubber washer at pommel: Between handle and guard: It also serves as a loose glue (you can still easily take-down the knife). I stuck the guard on with it. It also tidies up the joint line: And it can be used to bodge/fill. Here the scales have moved away from the blade so I just stuffed Sugru in the crack: I've only just done this.. so cannot comment on longevity.
  6. I've not really understood why BCC is less dense even though I 'lucked' into the explanation with the above post. I found the unit cell sizes of BCC anf FCC (both at 912C) here: http://www.cmse.ed.ac.uk/MSE2/IronStructure.pdf A simple bit of Pythagoras shows that in going from FCC to BCC the FCC unit contracts in one plane but expands in the other 2, resulting in a less dense BCC but the space in between atoms for Carbon to dissolve is now squashed so although more volume, it isn't tall enough. And a single Carbon atom can't squash. I drew it out on a bit of paper...
  7. It is a OK rule of thumb but isn't accurate in all situations. My own rule of thumb: I'd suggest some tempering even if you want ultimate hardness. It depends on the steel composition.
  8. The same topic, pinned in Metallurgy forum, is well worth a read (or re-read: I'd forgotten most of what I wrote, let alone what 'the people who know' wrote).
  9. I don't make many knives. I make even less sheaths. I took this knife, almost finished, to Owen's hammerin last weekend and it got dropped. I had a feeling of doom that it was going on the floor long before it happened. So, to be able to relax at hammerins and save on sharpening I decided to have a go at a scandi sheath - my third sheath in 10 years. I'm amazed that it worked just by following an online tutorial. Maybe making sheaths isn't all that bad after all... but I may just stop while I'm ahead.
  10. How do they get all that Nitrogen in there? 40 hours soak at high temp in a nitrogen atmosphere? How sure are we of the quoted Nitrogen level?
  11. That is really interesting. Thanks! A much better experiment and report than I would have done. If I do get around to doing such an experiment, then I will not put any clay on the blades - I can still expect up and down sori can't I? Also, in the only video I have seen and from a description of the quench process from Don, a water quench starts with the tip bending down before moving back again. Do we have any evidence that upward sori can occur without being preceded by downward? Maybe oil and water quenches start the same, tip down. Oil then results in the movements freezing at the tip down stage. Water (and now hot oil) allows the movement to continue and turn to upward curve before things are frozen? It would also be interesting to find out residual stress distribution in a downward sori i.e. are there compressive stresses along the blade edge? Have people had edge cracks in downward sori blades?
  12. Does anyone _know_ if there is any consistent difference in martensite distribution in the blade cross section between upward and downward sori? I don't suppose anyone is willing to chop a couple of swords in half to find out? I have a feeling that if I spent the hours conducting such a test then I wouldn't be able to detect a difference. I had a sword that went up at the tip and down towards the handle. It ended up in cleanly broken bits which would have been perfect to analyse if I hadn't been in the middle of redoing heat treat when the breaks occurred
  13. I've been reading a popular science book and wikipedia pages on thermodynamics and this has moved my understanding of temperature on a bit. Absolute zero is where all the bits that make up your 'thing' are at their lowest energy state. An example of energy state that I remember from my schooling is the position of electrons in the atom's rings. So at a low energy state, all electrons are at the lowest energy orbits. There are other 'states' like electron spin etc but my head can't grasp why some spins would be higher energy than others. Infinite temperature is when all the bits in your thing are evenly distributed amongst all the energy states. Random. Maximum Entropy. That leaves a lot of room for other conditions - like, for example, what if all your bits were are their highest energy levels and none were at the lowest? It turns out that that is negative absolute zero. So, the thing with the most 'heat energy' is negative zero. Negative infinity has a little more heat than infinite temperature. If you 'excite' the bits in your thing so they take on unnaturally high energy states then you may be able to create negative temperatures. A theoretical example is a laser. My CD player is colder than liquid Helium! Not sure how that helps me make knives though.
  14. A couple of examples or rebar. A bit more carbon than the mild?
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