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Tim Mitchell

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Tim Mitchell last won the day on May 5

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About Tim Mitchell

  • Birthday 08/06/1975

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    New South Wales, Australia
  • Interests
    blacksmithing, knifemaking, wootz manufacture, carpentry, astronomy.

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  1. In the old blade sections that were welded there is a line of decarburised steel at the joint and the pattern is visible coming away from that. Naturally the pattern will disappear in the area where the blade was at heat for any length of time but it will come back under thermocycling. The blade would need to be reground and heat treated anyway.
  2. The answer is don't get it too hot... LOL. Al said that welding temp for Wootz 1.6%C was at a bright yellow which is just above the hot working temp (above Acm). So about 1100°C. That temperature will change for lower carbon wootz. He used to use cast iron shavings from brake drums between the surfaces to help the weld take more readily. He made a chevron blade once of alternating pattern welded steel and wootz. Now if you have too much graphite in the blade or if you have too much Sulfur, or Nickel in the blade then it will crumble if you try to weld it. Only clean wootz can
  3. The issue with refractory clays is that in a crucible they need to be resistant from acid attack and some elements in the clay can become liquid rather quickly when exposed to iron oxide and fluxes in the melt. It doesn't take much to cut your crucible in half and to leave you with a puddle of metal at the bottom of your furnace.. Been there and done that, rebuilt my furnace 3 times. If you want to experiment then make small crucibles with thicker walls so that the damage will be tolerated much better and you can come up with something that will work.
  4. Some people add some Aluminium, but it doesn't help the quality of the steel I have heard. The best way to avoid porosity (bubbles in the steel) is to have really clean oxide free metal ingredients and to allow it to sit at liquid temperature long enough to allow any excess oxides to bubble out. One other thing that people call porosity... sometimes the same word is used inadvertantly for both... is "Shrinkage Cavity". A shrinkage cavity comes from the size of the crucible (large volume of steel) , the diameter of the crucible (larger diameter gives more of a shrinkage cavity); kind of like
  5. Jerrod, adding Mn to steels is the old fashioned way of removing sulphur from the melt, and obviously it wasn't perfect or the Persians wouldn't have gone to the expense and bother of getting their ingots from India. Can you shed some light on a better solution... other than don't have sulphur Also perhaps you could add some information from your expertise on the negative effects of MnS on steel. Ditto on the copper it isn't an issue and many blades had significant levels of copper, it acts as a hardener in small levels and adds toughness to a point.
  6. Hey Will, as Daniel said, your Phosphrous level in the ingot is way too high (maximum is 0.05%), if you want to remove P from the ingot you can add Calcium Carbonate or shell to the melt and that will help to lower the level. P in an ingot will make the lines more fuzzy and less defined, cold short and to a degree hot short. The carbides increase in number but the contrast drops. The main problem though is that you have too much Sulphur (over 0.02%) which will make your ingot crack when forging too hot or too fast. The other issue is your Silicon level is a bit high (should
  7. I think that it would be so difficult to trademark my design even with first use as there are now so many similar designs out there and clearly not trademarked either, it would almost fall into common use in current times even though it wasn't back then. Once you trademark then you have to defend and that looks like lots of distasteful legality which I don't desire. I am considering my options for the future if this starts to become a more regular thing.
  8. Thanks Gerald, I did a search for Alpha Omega genearally and it is amazing how many people have this kind of symbol on various other businesses. When I started out 17 years ago I was the only one who had this kind of symbol in any business, all these are recent designs. He has agreed to change his design to prevent brand confusion, but looking at the number of similar designs out there this may become a problem for me in the future... It is something I will have to think about. I am not concerned with other businesses, mainly in the knifemaking field being an issue. There was an
  9. Hi all, I have been using my maker's mark on knives since around 2002 and today I came across a guy using a very similar makers mark. I am looking for some feedback concerning if I should ask him to change his mark or not. Mine is on the Ricasso and his is on the pommel of the knife. As you can see the marks are pretty close and his looks like a slightly stylized version of mine, essentially he has just lengthened the legs of the A. They look close enough to be confused by some customers which is something that I don't want. Please be free with your comments... I don't want to be a stick
  10. AA stands for Atomic Absorbtion and it is a kind Optical Emissions Spectrometry.... Just the old time word for it
  11. Will, you need to test for Carbon which XRF cannot detect. Any carbon determination using XRF is a subtractive amount and is worthless. Basically they use the elemental profile to guess at what your steel is and that can pinpoint your carbon, but yours isn't a standard steel and so they have nothing to compare it with and any carbon figure is a sum of all the errors in the detection of the other elements... worthless. You need to get Spectral AA analysis for all elements or you need to get Leco analysis for carbon, sulphur and then use XRF for Phosphrous, Silicon, vanadium, manganese etc.
  12. One other thing, the old method of using long roasting periods for ingots may have been to help remove any remaining sulfur in the steel. They would roast the ingots in Hyderabad for a long time, pull them out, hit one with a hammer and if it broke they would put them back in and roast them again. This was either because their carbon content was too high.... or it was because they were needing to get any remaining sulfur down to a level where their ingots were no longer hot short and could be forged. So if you do have sulfur in the ingot a good long roast will help to get some of it out of y
  13. Will, happy to help. The green glass is fine, it actually has some copper in it to create the colour and so that does help the melt a bit. Al used to use the green glass and it never caused him problems and that is what I use and have never had issues. Concerning heats... High heat is above Acm.... if you know what that is. Low heat is at least 100°C below Acm. So for 1.6% C ingot high heat is 1050 - 1100°C and low heat would be around 800°C. The issue is that if you have lower carbon (1%C) then your Acm point is 820°C and so forging at a mid orange heat is too high... However I thi
  14. Thanks Joshua, I will have to play around with this a bit. I loved the blade in that thread... very nice pattern and the coffee etch really is startling in it's contrast. I also like the comments about normalising and graphite spray to remove the lines... Were the lines due to decarburisation of the outside of the bars while welding? That is what it looks like to me.. Gary thanks for the info on your method too... I like the idea of going straight from the ferric into the coffee without cleaning the blade... it makes sense.
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