Hi All,
Interesting topic, but I think there are two issues with the Central Asian nomads. First, they did occasionally build cities (see various references), and second, because they often used carts to move things around (
link, near bottom). While mobile, they could also move a forge around as needed.
Following what Mark said, I think that the important thing is population size and material needs, not mobility. The Hordes were large and highly organized, so they found ways to move both metalwork and smiths. A small, isolated tribe might not have the surplus to support a smith, nor ways to get the specialized materials he needed. That said, I think the critical tests are the African tribes, because they were pretty small, and did metalwork. Hopefully one of our Africa experts will chime in with how that was organized, and how small and isolated a group of people can be, and still support a smith.
As an aside, I'd point out Wallace's
Malay Archipelago, wherein he describes what the smiths of Lombok used to make two meter long muzzle-loaders (
link). Yes, these aren't swords, but it provides an idea of how little a skilled smith needs to make a long weapon:
"At Mataram we called at the house of Gusti Gadioca, one of the princes of Lombock, who was a friend of Mr. Carter’s, and who had promised to show me the guns made by native workmen. Two guns were exhibited, one six, the other seven feet long, and of a proportionably large bore. The barrels were twisted and well finished, though not so finely worked as ours. The stock was well made, and extended to the end of the barrel. Silver and gold ornament was inlaid over most of the surface, but the locks were taken from English muskets. The Gusti assured me, however, that the Rajah had a man who made locks and also rifled barrels. The workshop where these guns are made and the tools used were next shown us, and were very remarkable. An open shed with a couple of small mud forges were the chief objects visible. The bellows consisted of two bamboo cylinders, with pistons worked by hand. They move very easily, having a loose stuffing of feathers thickly set round the piston so as to act as a valve, and produce a regular blast. Both cylinders communicate with the same nozzle, one piston rising while the other falls. An oblong piece of iron on the ground was the anvil, and a small vice was fixed on the projecting root of a tree outside. These, with a few files and hammers, were literally the only tools with which an old man makes these fine guns, finishing then himself from the rough iron and wood."
(There's more detail in the original quote. Follow the link if you're interested)
F