You don't need to change the shaft, you need to buy the correct feet for your machine. Different models use different style feet. On the 111W, the shaft for your rear foot has a slot that goes from front to back, and all the feet for that machine will take the same style feet. The rear foot is held on by a screw that goes in from left to right. The Singer 211W151 has rear feet that attach in a slot that goes left to right. Unless you're going to sew welts with welt cord larger than 5/32, you won't need any more welt feet.
No one lives forever, the trick is creating something that will.
Last edited by DanTwoLakes; 09-20-2010 at 08:41 AM.