How To Bridge The Gap or
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  1. #1
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    Default How To Bridge The Gap or

    The OD is smaller than the ID.

    First, I am painfully aware that a vast number will express their concerns about the practicality of this project and even question my sanity for even attempting it. Please resist the temptation and keep your comment to solving the problem at hand. Your reward in heaven will be great.

    I wish to mount a bayonet lug on the barrel of a rifle. The problem is the inside diameter of the ring of the lug that slides onto the barrel is larger (ID = .655) than the outside diameter of the barrel (OD = .618). That means, if I did the arithmetic right, an all around gap of .0185 between the lug mounting ring and the barrel.

    My first thought was to plug the hole for the barrel in the lug with either a force fit or brazed/soldered in plug. Then drill/ream the proper size hole to fit on the barrel. I no so sure that is a good idea. As after putting in the hole, the walls of the plug will be really thin.

    When looking into brazing/soldering an unmodified lug to the barrel it appears that a gap of .020 can be accommodated. Remember, the gap between the lug ID and the barrel od is .0185 all around. Spacer wires/shims would be used to properly position the lug and to create a consistent gap for optimum flow in the joint.

    I am thinking brazing/soldering is the way to go but I am open to other ideas on how to attach the lug to the barrel and why they would be better.

    There is one perfect solution to the problem. I came up with a design that is sized to correctly fit the barrel. Unfortunately, no one is willing and or capable of executing my design. If you think you have what it takes contact me and I will send you the drawing.

  2. #2
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    All been worked out 150+ years ago.....Snider bayonets were bushed to fit the Alex Henry rifle,Martini Henry triangular bayonets were bushed to fit the smaller 303 barrel of the Martini Enfield.Pattern 1887 and 1888 bayonets were bushed to fit the 303 conversions.No need to reinvent the wheel,

  3. #3
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    Perhaps you could bore the bayonet socket out a little larger to make your bushing a little thicker?

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    When I go to garage sales and flea markets, I look for feeler gauges.
    They make a handy assortment of shim stock for just such projects.
    Maybe line with a .020" and ream to perfection.

  5. #5
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    First of all IMO brazing may cause more problems than it solves due to high temperatures. Soldering should be plenty strong enough.

    To bridge the gap, 2 options.

    1. Bore out the lug so you can use a thicker walled bushing.
    2. Bend a shim of appropriate thickness to fill the gap. This will most likely require annealing the shim.


    Annealing a steel shim is likely to cause a lot of scale unless you exclude oxygen. Methods range from a controlled atmosphere furnace to brown paper and stainless steel foil wrap. In the latter method the paper chars and absorbs the oxygen.

    A brass shim on the other hand can be annealed quickly by heating red hot and dunking in water. Usually this only causes thin oxides that can be buffed off or pickled in a mild acid.

    I would bend and trim the shim to wrap around the barrel and then flux the barrel, the shim, and the inside of the lug and solder all with one heat.

    Just one man's opinion but I think this would give far superior results to using pins as spacers.

  6. #6
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    If you know what to look for you can find combined silver solder and flux in a paste. Make your spacer ring .002-.004"
    undersized and paste both the ID of the bayonet (after cleaning and sanding) and the OD of the spacer ring, push it in and heat to tinning temperature. If you want to make sure you have a high percentage of silver solder contacting both surfaces you can add some SS wire to the joint while at temp.
    Then after it cools ream to size, the silver solder should supply the necessary strength.


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