Bonding a tube inside another

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  • Bonding a tube inside another
  • IanMunro
    Member

    Something like loctite 603 would be my choice. The metal’s probably going to sheer before it does, and if you ever need to separate the parts just heat em up with a gas torch.

    Premier Icon maccruiskeen
    Subscriber

    any reason not to braise or solder it?

    CountZero
    Member

    Loctite, I would guess, as first choice, then a two-pack epoxy, like the Maplins type that comes in a sort of syringe, because it’s very thin and runny, but sets in an hour, so would fill the small space. I wouldn’t use cyanoacrylate, because it’s brittle when set; it was designed to glue flesh in surgery, instead of using stitches.

    Premier Icon molgrips
    Subscriber

    Well I don’t have loctite.. Will the epoxy do ok? How much space to leave? 0.1mm?

    Premier Icon maccruiskeen
    Subscriber

    What about a cyro-fit. Like what fork stansion are done by. Get the inner bar machined to the same dia as the internal of the tubes (I’d not trust the internal dia to much – so maybe get that machine to a known size at the same time) Stick the inner bar in the freezer, put the outer ones in the oven then shove them together.

    Any reason not to buy one tube thats the right length in the first place?

    Loctite, I would guess

    Loctite is a brand name covering a multitude of glues and resins for different applications. There maybe one right Loctite for this but there’ll be lots of wrong ones.

    Premier Icon richmars
    Subscriber

    Agree about shrink fit the inner (cool it down so it fits, but is an interference fit when at room temp)?

    crikey
    Member

    Hmmmmmmmmmmm.

    Is this possibly a molgrips special?

    What are you actually doing, and is there a perfectly simple, probably cheaper, undoubtedly much less hassle way of doing it?

    Or could you perhaps just buy one? 😀

    Premier Icon molgrips
    Subscriber

    Not sure about cryo fit.. Could be harder than glueing. Can’t get a good finish on the parts and glue would benefit frm a rough finish whereas cryo fit would not.

    It’s currently a nice tight fit with no play.. I think I may do a test piece.

    Crikey, it is a bit of a “special” yes but justified in this case I think. I will write it up in a new thread when finished 🙂

    Premier Icon molgrips
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    I’m joining two pieces of tube together with a smaller diameter tube inside the two. I’m machining the joining tube out of something else, so I can choose how well it fits. I can’t pin it, I can only glue it

    I’ve bought ‘super strong’ metal epoxy for the purpose. So there are two questions:

    1) Is epoxy going to be better than cyanoacrylate?
    2) How tight should the fit be? Too tight and there’ll be no glue left to bond, won’t it? I’ve made a bit that slides in and out perfectly, should I make it more of a press fit?

    It’s only about 8mm diameter overall, so it’s pretty small, and it needs to take a bit of torque.

    crikey
    Member

    The reason I’m asking what it’s for is because I was watching a guy using a canal pole to fish with today. Basically a series of carbon fibre tubes, all slightly smaller than the previous one..

    I know this may have nothing to add, but it might give you more ideas?

    Premier Icon footflaps
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    I had to bond two plastic pipes together to make the U bend I needed to fit a modern sink to an imperial outflow pipe. I used a waterproof epoxy which could set when wet, worked fine – not leaked a drop.

    sugdenr
    Member

    Depends how much torque you need to transmit, interference fit is favourite (cryo fit) but if you are bonding steel its likely the tube is continuous welded so has an internal bead in the way and actually that round. For glueing, in any case the fit wants to be uber tight, tap fit not push fit – because the glue does not really bond so much as fills in the microscopic gaps in the 2 parts, the glue has little strength itself, just gets in the way when they try an move if you like. Machine a slight ramp on the ends to help get it started.

    compositepro
    Member

    whats the something else made out of?

    in fact what are both bits made out of?

    because the glue does not really bond so much as fills in the microscopic gaps in the 2 parts, the glue has little strength

    are you sure?

    Knowing the intended application may help us advise on the bonding process?

    Premier Icon molgrips
    Subscriber

    Well it’s done. Fit was nit exactly tight. Finger push fit but no play. Glue went on and it within 5 mins it could not be turned by finger pressure. Fingers crossed. Will write it up this evening once I have given my kids some attention after spending all afternoon in the garage 🙂

    Premier Icon Brainflex
    Subscriber

    I see you have finished but I would of tapped a thread on all parts and used Loctite. That way when you tighten the final fitting it locks everything together. Good job tho.

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