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  1. #1

    Default To braze or to weld?

    Guys,

    I have a C clamp which is part of a collectible item* and which C clamp is effectively made out of a piece of square rod, which has been bent at either end to form an "C" and to the one end of which a screw mechanism has been welded on. The thickness of the square rod from which the clamp is made is probably no more than 10 mm, possibly a little less at around 8 mm or so..

    On this clamp, the one "corner"(which is to say where the square rod has been bent at 90° to form the one arm of the "C"), the joint has been previously welded, clearly as a result of material failure. It appears, on inspection, that the welding does not go very deep into the material and is rather more a superficial weld. Recently, while using the clamp, that weld has also now started to give way (on the inside of the 90° bend). My sense is that I should grind away the welding and then look to braze the joint and at the same time, to introduce some of the brazing material into the "elbow" of the 90° bend so as to strengthen it and make it less likely to tear in the future.

    Would I be best off repairing this joint by brazing it as aforesaid or rather by welding it?

    Edit: Or should I silver solder it?


    *For reasons of dimensions, a conventional commercially available C clamp is not an appropriate substitute.
    Last edited by Wanderin' Zero; 26-05-2017 at 10:09.
    Quemadmodum gladius neminem occidit: occidentis telum est.

    Seneca (4 BC - 65 AD)

  2. #2
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    Default Re: To braze or to weld?

    I would guess that a proper weld should be much stronger than brazing, simply because steel has a higher tensile strength than brass.

    The secret to a strong weld lies in the skill of the welder. It is of utmost importance that the weld should penetrate all the way to the core of the base material, and not just be plastered on top. To do this, the material around the break line should be cut (ground) away to form a 90 degree V, all the way to the centre, from all sides. If properly prepared and welded, the weld will be stronger than the surrounding material. If it breaks again, it will be next to the weld, not trough it.

    You could even remove excess material from the weld so the object follows the original contour, if an authentic look is desired.

    Find an expert welder who can do it properly.

  3. #3
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    Default Re: To braze or to weld?

    I doubt that silver solder or brazing will be as strong as welding. Maybe see if you can get it TIG welded.


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    Default Re: To braze or to weld?

    Is the original clamp made of steel or wrought-iron? This will make a big difference as to how you can fix it.

    Why not make a new clamp from commercially available materials for functionality but keep the 'old' part from a collector's perspective without changing it too much?

  5. #5
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    Default Re: To braze or to weld?

    Quote Originally Posted by A-R View Post
    .. the material around the break line should be cut (ground) away to form a 90 degree V, all the way to the centre, from all sides.
    +1

  6. #6

    Default Re: To braze or to weld?

    rgm, I don't really know what its made of to be honest. I think it's bent steel but who knows? It's old postwar commbloc stuff. It may be a possibility to modify a commercially available clamp for use in context.

    Re brazing vs welding I was thinking a brazed joint tends to be less brittle (which is one of the reasons it is used in some contexts) and also that I could add some filler to the inside of the corner to act as a strengthening gusset (though I could puddle some there while welding) also known as a "fillet". Maybe I''ll clean it up, grind it open to get proper penetration and then weld it I|(I have a very good welding machine and can help myself some). If it fails again I'll see if brazing works.
    Last edited by Wanderin' Zero; 26-05-2017 at 10:36.
    Quemadmodum gladius neminem occidit: occidentis telum est.

    Seneca (4 BC - 65 AD)

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    Default Re: To braze or to weld?

    If it's good old "pot yster" welding will just make it brittle and break it further but you can get specialised welding rods for this type of welding.. If it is steel, welding will be your best bet as explained by others here.

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    Default Re: To braze or to weld?

    Quote Originally Posted by rgm108 View Post
    If it's good old "pot yster" welding will just make it brittle and break it further but you can get specialised welding rods for this type of welding.. If it is steel, welding will be your best bet as explained by others here.
    If you are referring to cast iron, that's not really a suitable material for a G-type clamp. It is brittle and has low tensile strength. It can be brazed, as long as the whole piece is well-heated (crerry red) to prevent heat stresses.

    Cast iron is usually easy to identify due to it shape, showing the mold lines and "sandy" surface texture on unmachined parts. It can not be bent into shape. Only the English will make a clamp out of cast iron...

  9. #9

    Default Re: To braze or to weld?

    Thanks A-R. This is definitely not cast. Polish copy of a Russian design.
    Quemadmodum gladius neminem occidit: occidentis telum est.

    Seneca (4 BC - 65 AD)

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