Bison chucks...
I have a friend who is a machinist by profession. When I saw a Bison chuck on ebay, I asked him how good they are. He told me they are some of the best on the market, that's why they are so expensive. The Bison chuck is what Joe Porper puts on his Model B lathe right from the factory. I bought the one I saw on ebay, 5.5" size, and my machinist friend was really surprised at the great deal I got on it. I had him use one of his mega dollar lathes to fabricate a mounting plate and bore the through hole to 1.375", so I could put it on the other end of the spindle on my Model B. It works great having a chuck on both ends of the spindle, and the bigger chuck with the bored out center takes the full size of the butt without any problem.