I have access to a couple of shamisen that have been completely disassembled, and I want to put them back together. I was wondering how the body and neck are usually connected.
The one that I have been practicing on has a metal cap that seems to hold the body onto the neck. Otherwise, is it just the tension of the strings keeping it together?
Usually, the nakago section of the neck fits so tightly to the body that it can stay together just from that
Thanks Bryan. I’ll have to check them again. I have three disassembled ones, and it’s probable that I just had a mis-matched pair.
Nick, a brand new shamisen neck will fit really tightly in the dou, but with time and wear it does get looser. I have some that are only held on by string tension, which is still ok, but if there is any room to wiggle the neck around in the hole, you’ll want to do something about that.
Welcome to Bachido, Nick!
As Gerry said, time will wear down a shamisen neck. You can make a shim from a very thin piece of wood and glue it onto the neck so it fits tightly again.
Also, if it doesn’t fit, it might be mismatched, or might because the wood has swelled. It should be tight, but shouldn’t require a supreme amount of force. If it feels unusually hard to put in, you can lightly and slowly file the square hole in the dou until the shamisen fits snugly in.
If you feel like it, feel free to post pictures of your three shamisen here! 
Thanks, it’s nice to be able to ask questions of y’all. I’ll take pictures tomorrow and post them.
The reason the shamisen are disassembled is that all three are lower quality and the necks warped pretty badly within a year of purchase.
I took one of them to a local luthier and he said there wasn’t much that could be done about the twist in the neck, but that it shouldn’t make a huge difference to play-ability. He said that some high-end custom guitar makers intentionally build a little twist into the necks for ergonomics.
The shamisen haven’t been touched for years and I was hoping to get at least one of them back into playing shape, assuming that the warped neck doesn’t affect it too negatively.
Thanks for the responses. I’ll let you know how the project turns out.
On a side note, does any shamisen player on the forum live in the Houston Texas area?