We don't run any knife rolls, too expensive. The fluted stalkrolls we can rebuild. On the drive shafts I actually think it's the other way around. They are hardened, otherwise the hex would get wallered out in the row units. They often break where the collar is welded on, on the outside. The weld probably interfears with the hardening. You have to keep one thing in mind. The engineer who designed the cornhead figured it would use around 7hp per row unit. After about 20 years, in fall of 2002, the JD engineers finally came out and actually measured the power used. It was more like 13hp per row unit. This is why shafts and reversers are breaking. In 2003 you could buy an extra high capacity reverser on the 50 series. The gears in it are physically wider than on the high capacity version.