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  1. #31
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    Quote Originally Posted by AndrewOC View Post
    Bob
    Thankyou thankyou thankyou for that most clear perspective setting of The Zinc Issue!
    There has been much flapping about how murderous zinc is, with poor evidence in support. Often from fag sucking, gun toting, boozers (i.e. hypocrites).
    At work tomorrow I'll ask the Librarians for the research. What stuff have you come across? I would love to share it on other forums.
    A.
    I agree, it's kinda sad how paranoia seems to be rife about stuff that is manageable while things we should have paid attention to like smoking has taken centuries to get people to think about.
    In someways it's understandable how fear of the unknown leads to exaggeration and a few rounds of Chinese whispers later and it's more dangerous than ebola.
    High concentration ZnO fumes have an immediate effect which causes those exposed to sit up and immediately take notice.
    ZnO effects are unfortunately tangled up with the the effects from more toxic metals like Cd and Cr which can do things directly.
    ZnO exposure apparently does not kill directly but increases the chance of getting other pulmonary diseases like pneumonia.

    BTW definitely be careful with old Zn compared to new Zn as old Zm has more Cd in it. It was not until the 1960s that Zn processing was changed to better remove the Cd from it.

    I've worked with just about every element on the periodic table during (including some pretty toxic and radioactive materials) during my working life as a research scientist and I on a scale of 1 (least dangerous) to 10 (most dangerous) I would put ZnO is the less than 5/10 category.

    I do know what it's like to have my breath taken away by fumes from welding galv which is why I put certain things like ventilation in place in my shed.
    Of course I don't advocate welding the stuff willy nilly but the problem basically becomes a non-issue just by using a decent high flow extractor and if you happen to get a faint whiff or two every now and then it will not kill you.

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  3. #32
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    Feb 2006
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    Perth
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    I haven't fired up the furnace for nearly 12 months and finally an excuse to do this came up via the mens shed where one of the guys was interested in making a couple pf practice knives from old files.

    He had tried to soften the files using an oxy but all he succeeded in doing was bending one of the files. Then he tried to straighten it on an anvil and the file shattered indicating that the oxy was nit getting them hot enough for long enough. At this point I offered to soften them in my gas furnace.

    5 minutes to warn up, 10 minutes at~!1150 then the gas was turned off and they were left to cool down inside the furnace.
    There was still a faint visible red glow coming from the gaps around the furnace door after 30 minutes and 2 hours later the blanks were still around 300, 3 hours after that they were 80 and I pull them out.

    One of the blanks (the one directly under the torch, was bent but it straightened easily and a file was easily able to remove metal indicating they had well and truly been softened.
    They look pretty manky but the scale layer is quite thin.

    Now lets see what he can do with them.

    Building a natural gas forge - WIP-img_5814-jpg
    Attached Images Attached Images

  4. #33
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    Perth
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    I had the opportunity to acquire this some months ago from a relative of a member and have just got around to tidying it up

    I took some photos of it when I first got it in all it's rusty glory, but now I cannot find them.

    Anyway here it is after a quick once over with a wire brush on an angle grinder and the first coat of tannic acid.
    It's probably going to need a half dozen coats to arrest the rust.
    You can see that from the state of the rust inside the die holes.

    Building a natural gas forge - WIP-img_5839-jpg

    An here it is after its second coat of tannic just applied.
    Building a natural gas forge - WIP-img_5843-jpg
    Attached Images Attached Images

  5. #34
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    Dec 2007
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    Melbourne
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    Nice swage block. I hope you put it to good use.
    ..Live a Quiet Life & Work with your Hands

  6. #35
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    Mel from the men's shed who is doing the knives did some more work on them today.

    He could use a machine to form up the main bevel but he saw this bevel forming jig on the web and wanted to try it out.

    That's a pretty ordinary and well used file he's using but it seems to be fair hogging out the metal so it looks like the annealing process has worked really well.

    Building a natural gas forge - WIP-mel1-jpg

    Building a natural gas forge - WIP-mel2-jpg

    Building a natural gas forge - WIP-mel4-jpg

    Building a natural gas forge - WIP-mel3-jpg
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  7. #36
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    an excellent build Bob

  8. #37
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    Nice cold day today in Perth so time to fire up the forge/furnace again.

    One of the other blokes at the mens shed had a small 100 x 250 mm (16kg) steel billet that he wanted to turn on a metal work lathe but it turned out to be hard as . . . . . . so I offered to anneal it for him.

    This is by far the biggest/heaviest piece of steel I have put into the forge.

    Heat up time to get to 1000 was about 15 minutes and then it took another 15 to get to 1180C .
    The temperatures are measured by an optical pyrometer targeting the cooler outer end of the block.
    On the picture it doesn't look anywhere near that temperature but that is caused be a couple of things
    - by the time I open the door and futz about with the camera the end of the billet starts to cool off
    - another issue is that the camera cannot handle the dynamic range of light intensity and what it means is that the bright yellow bits are much hotter.
    Photos are taken using a tripod from about 3m away because of heat
    Building a natural gas forge - WIP-warminup-jpg

    After 5 minute os so at that temp the walls of the furnace near the door which are not insulated start to glow red
    Building a natural gas forge - WIP-hotdoor-jpg

    At this point I backed off the gas and reduce the temperature to 1080C and held that for 30 minutes.

    Now the flame is not so hot and I preset up the camera on a tripod and whipped the door open and took the photo before the end of the billet started to cool off.
    Now you can see the whole billet.
    Notice how the lower fire brick door has cracked.
    This is probably the 30th or so time the furnace has been run so I guess that's not too bad.
    I have plenty of bricks and will have to remake the door and improve the frame so it will hold a cracked brick for when that happens again which is inevitable

    Building a natural gas forge - WIP-1080-jpg

    For the first time the CO sensor alarm went off - had the shed door closed - opening the door allowed the ventilation fan to clear the shed in a couple of minutes.

    Here is the cooling curve for the billet.
    I would have liked it to be a bit slower
    its similar to that for the knife blanks indicating that it's the furnace itself that dominates the cooling - cracked door probably doesn't help much either.

    One possibility was to put it in a box full of lime - one problem is not having anything to pick up a 16 kg lump of steel at 1080C

    Building a natural gas forge - WIP-cooling-curve-jpg
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  9. #38
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    You never cease to amaze me bob

    I could use one of them furnaces atm. It must have a good impact on temps in the cave brass monkey weather here atm

    Dave TTC
    Turning Wood Into Art

  10. #39
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    Quote Originally Posted by DaveTTC View Post
    You never cease to amaze me bob
    I could use one of them furnaces atm. It must have a good impact on temps in the cave brass monkey weather here atm
    Dave TTC
    Turning Wood Into Art

    It sure does help warm up the man cave.
    The furnace can generate ~22kW of energy and that has to go somewhere!
    When it's cold there's a temptation to not vent any of the exhaust but it's essential to do so.
    I have the welding booth exhaust running at 1200 CFM and the dusty running at 1200 CFM - I have another exhaust fan but I didn't need that today as it was pretty cold here - well for Perth anyway.
    Outside it reached 15 but the temp in the man cave got up to nice 25.

  11. #40
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    Adelaide
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    Quote Originally Posted by BobL View Post
    The furnace can generate ~22kW of energy and that has to go somewhere!
    .

    22kw...ruddy hell my radiant gas heater (5 panel) only does about 14kw and thats nice...but the running costs ...well she just screams n screams until summer....one she wont stop cos I do have plans to put in an aircon unit.

    am waiting to see the end product also...so make sure you get some pics when they are finished

  12. #41
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    Quote Originally Posted by eskimo View Post
    22kw...ruddy hell my radiant gas heater (5 panel) only does about 14kw and thats nice...but the running costs ...well she just screams n screams until summer....one she wont stop cos I do have plans to put in an aircon unit.
    Running cost is about $3/hour but unlike a heater I don't usually have it running for very long. About the most I have had it running continuously is 90 minutes. Unlike a charcoal setup it's easy to turn it off and on although of course warm up time is still required but if it' has been off for no more than half an hour it warms up really quickly.

    am waiting to see the end product also...so make sure you get some pics when they are finished
    Will do.

  13. #42
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    Very impressed- nice job Bob.

  14. #43
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    Quote Originally Posted by Grahame Collins View Post
    Very impressed- nice job Bob.
    Thanks Graeme,

    I did some more annealing on the weekend.
    I have been buying scrap steel discs from the local steel merchant ranging in size from 3 to 18 mm thick and 50 to 400 mm in diameter.
    It's the same stuff I used to make the base and turntable for my ti-grinder.


    The discs are obviously cut with some sort of plasma cutter so the edges are very hard and make mincemeat out of HSS.
    Besides this, these discs were way too big for my little Hercus so I took them to work and turned them on the big Nutall with carbide tooling.
    It's not just the edges that are hard this stuff is way harder than mild steel so drilling and tapping was a PITA and I remember breaking three 3/16" taps mounting those turntable bearings.
    Young Ron from the Mens Shed (he is 85 years old) reckons it's some king of Bisalloy plate
    Last weekend I decided to make something from one of the 150mm discs but knowing how hard they were I decided to see if they could be annealed.
    They just fit inside the forge and yes they did get a lot softer.

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