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Thread: Cold rivet snap size help please

  1. #1
    Associate Engineer
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    Cold rivet snap size help please

    Hi, I'm a complete newbie here, a complete novice too.
    I'd like to get into small scale model engineering...but as a hobby only.
    This site looks fantastic, and there appears to be a wealth of knowlege here, and at some time in the future, I'd love to be able to contribute maybe.

    Anyway, I'm wondering if there are any resident 'Yoda' types here that can help please? (Fingers crossed )

    I need to do some cold riveting.
    The rivet size is fairly small, and the shank rivet diameter is 5.5mm, or 0.21" (or near, that's the closest I could get on my vernier)

    What I really need to know is what size snap do I need to get a nice round head when it's beaten down please?
    I've tried to work it out....and I'm thinking iro 1/8" to 3/32" ?

    I've bought a 3/16" round head snap off ebay, but found it's a bit big...wayyy too wide and deep, so I'm a bit confused, what size to order next.
    As there possibly will be many, many rivets involved, I'm hoping to use my trusty air chisel which takes .401 dia snaps to peen the rivets over.

    Just wondering if anyone has an idea or if there's a standard size I should be going for please.

    Appologies for dropping a question on you guys with my first post

    Sorry, I've duplicated this post, I think I posted on the wrong part of the forum.
    Mods, please feel free to move/delete as appropriate. Thanks.

  2. #2
    Administrator Kelly Bramble's Avatar
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    What I really need to know is what size snap do I need to get a nice round head when it's beaten down please?
    I've tried to work it out....and I'm thinking iro 1/8" to 3/32" ?


    Your terminology confuses me. Are we talking about a pop-rivet? Can you clarify with a picture of the rivet?

  3. #3
    Lead Engineer RWOLFEJR's Avatar
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    I'm pretty sure the snap is the dolly or punch used to shape the end of the rivet where it pokes through the things needing joined. Like a flat ended punch but a little dome shaped pocket in it. You back up the preformed head side with a dolly or plate if you don't care if you flatten the dome a little bit... or if it's a flat head rivet... Then put the snap on the stub of round cylinder shape sticking up and swat it a few times.

    I'm guessing the "snap" you bought would be fine if you had more rivet to move... or more protruding from your pieces to be joined. I'd grind the pocketed end down until you get what you want. I would've thought you'd need something more like 1/4" diameter dome or even a bit bigger to keep from pinching the dome edges? As I said... I expect it's more that it's too deep for the little amount of material you're moving.

    Once you do find out what works... I'd consider buying a couple of chisels for you air chisel... cheapest type you can buy... and modify it yourself. Cut off the end of the chisel to where the shank is round with a grinder or cut of blade. Heat the end of the round shank where you cut it off to about 1,600-1,700F and slooooow cool. Maybe even wrap it in insulation or poke it into a can of oil dry or vermiculite. Next dust the end off where you cut it so it's nice and flat. Then take a drill or ball end mill etc. and drill a little pocket into the end of the chisel. A 135 degree drill... a 118 degree drill... a ball end mill... will give you a little different shape on the rivet but I'd guess a drilled pocket would still produce a pretty good looking peen. Try it out on some scrap while it's still soft. Go deeper or dust a little off the face if too deep. Go larger diameter drill if the outer diameter of your peen is getting pinched. Once you get a hit on the thing that looks nice heat the end of it back up to about 1,700 and then drop it in some oil. We call that hillbilly heat treating. MAKE SURE YOU WEAR YOUR SAFETY GLASSES...! The chisel will be full hard and a little more brittle than "store bought" that would have been tempered back a bit... and probably double tempered.

  4. #4
    Associate Engineer
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    Sorry.

    The rivet I'm referring to is made of mild steel.
    It has a 'mushroom' style head, and when it's peened over, both sides of the work have a semi spherical 'mushroom finish.
    This style of rivet, albeit much larger was used in early shipbuilding and boiler making.
    The snap (nothing to do with pop-rivets) is basically a mandrel that is struck with a hammer which forms the end of the rivet and fastens the work together.
    In my case though, the snap will be driven by an air tool, rather than being struck by a hammer.

  5. #5
    Administrator Kelly Bramble's Avatar
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    OK, you're from the UK, welcome to Engineers Edge!

    As far as the size of the "Snap" you need to match the button head radius. On the opposite side the rivet will form a natural mushroom shape by just bucking the rivet into place.

    The rivets you are referring to are called Universal Head Rivet (also called Button Head).

    Here, in the USA we have different names for these tools.

    Air Tool = Rivet Gun or Rivet Air Hammer

    Snap = Bucking bar (used opposite the rivet bit on the rivet to form the head). Some folks in the US call it a "snap".

    Mandrel = Rivet set & Dimple Dies (Used on the Rivet Air Hammer)

    Just for fun - here are some riveting videos:

    Flush mounting riveting

    Aircraft Sheet Metal Layout

    Installing Aircraft Solid Rivets

    Riveting for Re-Assembly

  6. #6
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    Thanks for your help people.
    very much a[ppreciated.

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