I like dizing when making sewing
thread or sock yarn. It organizes the fibres and makes them far more parallel than carding can do alone. And of course, it's necessary if we are making true worsted yarn (as opposed to worsted style, which is also lovely).
For these socks, I was working with a Jacob base (which has a strong crimp so is usually spun woolen style) and all sorts of little odds and sods left over. The fibres are different lengths. The llama almost 8 inches long, some other bits under an inch. If I were to spin this from the batt, the natural tendency would be for a slightly textured yarn. From the batt, it would make a good single for socks. However, I wanted a three-ply sock yarn. When spinning that fine, I don't like to struggle with the fibre. I want the fibre to naturally match the yarn, so I dized it off the drum carder in lovely long rovings and it spun up like a dream, to very consistent and smooth singles. Once plied, the springy nature of the Jacob showed through in the final yarn, but it was like working with combed Corriedale.
Here's another batch of yarn I did with different fibres.
Like any spining tool, a diz has its uses. I like it for combed fibre, colour blending, spinning fibres of different lengths into a smooth yarn, and for stretching the range of yarn that a specific fibre can make. It's not for everyone or every yarn, but if you can learn to use it, it can expand the kinds of yarns one can make.