If your mill is worn out, or if you dropped it, and now the drive shaft wobbles, or you want to upgrade to the larger drive shaft on the small mills, we offer replacement drive rollers. The standard 1144 alloy steel on our mills should last between 12 and 15,000 lbs of grist. If your mill feeds intermittently, or not at all, then your drive roller could be worn out. The drive shaft is integral to the roller, ie, it's all one piece of metal, so if the drive shaft gets bent for some reason then you might want to get a new drive roller. We always recommend the 1/2" shaft over the smaller 3/8" shaft if you have the drill to drive it. The larger 1/2" shaft is much more sturdy, and less likely to get damaged. All replacement rollers with a 1/2" drive shaft will automatically ship with a new drive shaft bushing so you can upgrade to the larger shaft if you currently have the small one. You will need a bench vice, arbor press or other press to install the replacement bushing. These rollers are 6" long and 1.5" in diameter. They fit all of our base level MM-2 and MM-3 mills.