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  1. #1
    BobL is offline Member: Blue and white apron brigade
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    Default My second attempt at steel bluing

    Some of you guys might be interested in this post in the Hercus forum about a small rotary table attachment for a Hercus lathe. It also shows my second attempt at steel bluing.
    Here's one of the pics.
    IMG_3058.jpg
    The rotary table is a cheap and cheerful bobbie from H&F. The bracket and tool post are the bits I made up and blued (or in reality, "blacked")
    Last edited by BobL; 9th Jun 2020 at 11:39 AM.

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    It looks fist class to me , blacked or blued.
    Well done!

    What is the application for it?

    Grahame

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    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Grahame Collins View Post
    It looks fist class to me , blacked or blued.
    Well done!

    What is the application for it?

    Grahame
    Thanks G,
    RE: Application:
    I would like to try and turn round or curved edges on small brass/ally hand wheels and knobs. I used a large (300 mm) rotary table at work a few years ago and had a lot of fun with it. The little table itself is a real cheapie so I am not expecting any sort of precision from it but in most cases this is not needed for knobs and hand wheels

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    BobL looks good mate, what process did you use for bluing? (hot, cold etc.) Cheers John.

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    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by calala View Post
    BobL looks good mate, what process did you use for bluing? (hot, cold etc.) Cheers John.
    Thanks.

    I used the room temp (cold) acid fume bluing. The recipe is a mix of what is on wikipedia and in Guy Lautard's Bedside Machinists book. It uses a chamber in which exposed containers of conc nitric and HCl are placed. If anyone is interested, next time I'm in the shed I can take some pics of my setup.

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    Ueee is offline Blacksmith, Cabinetmaker, Machinist, Messmaker
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    Looks good Bob.
    Some pics would be great.
    1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.

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    I'm interested Bob.

    I am having trouble backening cast iron, maybe this could be the answer. I know nothing about acid fuming. Is there a potential problem with corrosion?

    BT

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    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Ueee View Post
    Looks good Bob.
    Some pics would be great.
    OK - will do.

    Interestingly during my initial investigation of bluing (via books , internet and a gunsmith ) I found a lot of the info was clouded by a certain level of mysticism and BS i.e. "eye of newt, bat wings and a few incantations by the light of a full moon at midnight" but from my limited experience it seems to be just basic chemistry.

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    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Anorak Bob View Post
    I'm interested Bob.

    I am having trouble backening cast iron, maybe this could be the answer. I know nothing about acid fuming. Is there a potential problem with corrosion?

    BT
    Cast iron might have it's own peculiarities. How many times did you cycle through the bluing process?

    RE: Is there a problem with corrosion.
    Each acid fume exposure (I did it 12 times) is typically 5 - 6 hours of daytime and 10 - 12 hours overnight (it's been cold so the fuming and reactions are slower).
    If you forgot about about the pieces and left them exposed for a week or two, or a piece fell into the exposed acid containers I'd say there could be a problem.

    A close description of the fuming acid method I used is described on the Wikipedia Bluing Steel page. The exact same recipe with timing is provided in Guy Lautard's book. He recommends sulphuric acid in place of nitric. I used nitric because I already had some. Fume bluing is a slow time consuming method but it is said to produce amongst the most wear resistant bluing results.

    Bob, if you want to borrow my chamber and acid containers you are welcome to do so. The chamber is a 50 L plastic drum with a big clip locked gasket sealed lid so when it is closed it is very safe to transport.

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    Quote Originally Posted by BobL View Post
    Cast iron might have it's own peculiarities. How many times did you cycle through the bluing process?

    RE: Is there a problem with corrosion.
    Each acid fume exposure (I did it 12 times) is typically 5 - 6 hours of daytime and 10 - 12 hours overnight (it's been cold so the fuming and reactions are slower).
    If you forgot about about the pieces and left them exposed for a week or two, or a piece fell into the exposed acid containers I'd say there could be a problem.

    A close description of the fuming acid method I used is described on the Wikipedia Bluing Steel page. The exact same recipe with timing is provided in Guy Lautard's book. He recommends sulphuric acid in place of nitric. I used nitric because I already had some. Fume bluing is a slow time consuming method but it is said to produce amongst the most wear resistant bluing results.

    Bob, if you want to borrow my chamber and acid containers you are welcome to do so. The chamber is a 50 L plastic drum with a big clip locked gasket sealed lid so when it is closed it is very safe to transport.

    Bob,

    I had a quick skim through the Wikipedia article. Is the "rust" that appears on the metal black in colour? Also, is there any chance that you can expand on the carding process?

    The blackening that I have done has mostly been wet and cold. Some pictures here - http://www.woodworkforums.com/f65/no...3/#post1370920
    I used a product called Blackfast. There is no provision for double dipping. If the item is left in the backening solution for too long, sooting occurs. The soot washes off in the clean water rinse that takes place between each process. After the blackening the item is placed in a soluble oil solution. That knocks redipping in the blackening solution on the head.

    If your set up is as simple as it sounds and if I can get hold of the appropriate chemicals, I'd spring for my own outfit. Nothing worse that lending something to someone then needing it yourself. The bloke selling Blackfast reckons it was used by some serious manufacturers such as Kennametal and Seco. I'm not convinced that the kit that I have is the same stuff. A durable alternative has me keen.

    BT

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    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Anorak Bob View Post
    Bob,
    I had a quick skim through the Wikipedia article. Is the "rust" that appears on the metal black in colour?
    The rust is brown/black, its probably a combination of iron oxides and FeCl3 and Fe(N03)2 - I should ask the electron microscope boys to run a test on it for me. The ferric oxide is converted into ferrous oxide and latter two compounds are probably removed in the boiling water and carding process.

    Also, is there any chance that you can expand on the carding process?
    It's just using a fine wire brush in a moderate to light manner to remove any loose oxides. In the later repeated stages I switch to firm rubbing with fine steel wool. This is what takes time

    The blackening that I have done has mostly been wet and cold. Some pictures here - http://www.woodworkforums.com/f65/no...3/#post1370920
    I used a product called Blackfast.
    That looks pretty good to me - what's the problem with it?
    There is no provision for double dipping. If the item is left in the backening solution for too long, sooting occurs. The soot washes off in the clean water rinse that takes place between each process.
    The soot is just excess FeO or more specifically (Fe3O4). The same happens in the fume bluing process. After the first few repeats there is less brown and more black soot. Sometimes you get only a thin layer other times its quite sooty.

    After the blackening the item is placed in a soluble oil solution.
    After carding and I am happy with the evenness and thickness of the coating I then finally heat in very hot engine oil (fry pan on max).
    That knocks redipping in the blackening solution on the head.
    I don't think you need to apply the oil if you wanted to repeat, I would suggest carding and apply another coat of the Blackfast and see what happens.

    If you feel you have to oil dip before repeating you could always wash the oil off by boiling in a weak sodium carbonate solution, which is the way my process starts out to clean the grease and cutting compounds from the steel.

    If your set up is as simple as it sounds and if I can get hold of the appropriate chemicals, I'd spring for my own outfit. Nothing worse that lending something to someone then needing it yourself. The bloke selling Blackfast reckons it was used by some serious manufacturers such as Kennametal and Seco. I'm not convinced that the kit that I have is the same stuff. A durable alternative has me keen.
    Well I am quite pleased with the simplicity of the process. The durability is attested by the fact that every bit of loose stuff is carded off in between the fuming stages and the firm rubbing with the steel wool at the end seems to leave the firm surface untouched.

    BTW if you need a sealable 50L plastic drum to DIY then I can easily get one for you.

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    Quote Originally Posted by BobL View Post
    The rust is brown/black, its probably a combination of iron oxides and FeCl3 and Fe(N03)2 - I should ask the electron microscope boys to run a test on it for me. The ferric oxide is converted into ferrous oxide and latter two compounds are probably removed in the boiling water and carding process.


    It's just using a fine wire brush in a moderate to light manner to remove any loose oxides. In the later repeated stages I switch to firm rubbing with fine steel wool. This is what takes time


    That looks pretty good to me - what's the problem with it?

    The soot is just excess FeO or more specifically (Fe3O4). The same happens in the fume bluing process. After the first few repeats there is less brown and more black soot. Sometimes you get only a thin layer other times its quite sooty.


    After carding and I am happy with the evenness and thickness of the coating I then finally heat in very hot engine oil (fry pan on max).

    I don't think you need to apply the oil if you wanted to repeat, I would suggest carding and apply another coat of the Blackfast and see what happens.

    If you feel you have to oil dip before repeating you could always wash the oil off by boiling in a weak sodium carbonate solution, which is the way my process starts out to clean the grease and cutting compounds from the steel.


    Well I am quite pleased with the simplicity of the process. The durability is attested by the fact that every bit of loose stuff is carded off in between the fuming stages and the firm rubbing with the steel wool at the end seems to leave the firm surface untouched.

    BTW if you need a sealable 50L plastic drum to DIY then I can easily get one for you.
    Well Bob, I could not have asked for a more thorough response. Thank you.

    I have not tried reimmersion in the blackening solution after a rub down of the item. I will.

    My only real issue with the Blackfast is one of inconsistency of colour. Some items don't really blacken, they attain a greyish colour. I want black. I have resorted to using the flame and sump oil technique to blacken bolts and the like but even there the results can vary considerably.

    BT


    edit. Sorry Bob. I had not responded to your offer of the procurement of a drum. When you post photos of your setup I might be in a position to decide whether it 's a process I can manage. If I can cope I will put my hand up.

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    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Anorak Bob View Post
    Well Bob, I could not have asked for a more thorough response. Thank you.

    I have not tried reimmersion in the blackening solution after a rub down of the item. I will.

    My only real issue with the Blackfast is one of inconsistency of colour. Some items don't really blacken, they attain a greyish colour. I want black. I have resorted to using the flame and sump oil technique to blacken bolts and the like but even there the results can vary considerably.
    In the first cycle of the fume bluing the object only turns a pale grey, then with each successive cycle it gets darker and darker and was only starting to turn black after about 6-7 cycles. Even now it is not what I would call a dead black. I think some of this is relate to the lack of smoothness of finish of the original steel as Any edges are going to be affected by the carding process

    edit. Sorry Bob. I had not responded to your offer of the procurement of a drum. When you post photos of your setup I might be in a position to decide whether it 's a process I can manage. If I can cope I will put my hand up.
    No worries.

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    So Bob, the smoother the better? Smoothness tends to be the downfall of the sump oil technique. The carbonised oil doesn't adhere to smooth in my experience. Fuming seems like the perfect solution. I'm keener.

    Bob.

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    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Anorak Bob View Post
    So Bob, the smoother the better? Smoothness tends to be the downfall of the sump oil technique. The carbonised oil doesn't adhere to smooth in my experience. Fuming seems like the perfect solution. I'm keener.

    Bob.
    yep the gunsmith confirmed this and said the colour depth and hue depends on the smoothness and cleanliness of the starting surface. My finish was not all that shiny but it still came out quite smooth.

    With fuming the finish is so thin that accurately machined parts with fine threads etc should go back together without any interference.

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