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Tim Mitchell

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Tim Mitchell last won the day on December 10 2017

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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. 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.
  2. 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
  3. 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.
  4. 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
  5. 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
  6. AA stands for Atomic Absorbtion and it is a kind Optical Emissions Spectrometry.... Just the old time word for it
  7. 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.
  8. 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
  9. 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
  10. 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.
  11. Joshua, do you mix the mixture of Instant coffee with boiling water or do you use cold? This is the first time that I have heard about using a coffee etch. It seems some people use it on Wootz as well with success.
  12. A few years late.... but it wasn't anything that you did in polishing of the blade. The area along the entire blade edge where the pattern has dissolved is where the quenching of the blade has formed martinsite on the edge. This is common and expected to have the watered patterns at the edge be masked by the crystal structure of the blade. Martinsite is harder than the Pearlite body of the sword, but the price you pay for the hardness is that the pattern shows less well or not at all. Sword blades also are quenched to differing degrees due to their curve and that will affect the degree of m
  13. To answer your question specifically about thermocycling, the purpose of thermocycling is to soften the outside of the ingot in order to stop the ingot crumbling under the hammer as you forge if it has a little sulphur in it, so the thermocycling is done in a gas forge with a slightly oxidizing flame. This is normally done (by Al and myself) at around 1050 to 1100 degrees C for a 1.5% -1.6% C ingot. It does help to make the ingot easier to forge through the repeated annealing cycles, which applies to both a gas and coal. But if you do this in a coal forge you won't get the same effect of dec
  14. On reading this in the morning with fresh eyes I wanted to add something. IF you forged from above Acm and continued to forge the ingot as it cooled to be cool to the touch you will also cause problems. You should not forge the ingot to below the A1 temp (727°C) and if you did that using an ingot which was high in bloomery iron then you were approaching the area of causing problems from "Cold Shortness" as bloomery iron often has Phosphorous in it which makes the iron brittle if forged too low. I wouldn't expect problems from forging an ingot from around 900°C unless you did forge it too c
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