Prop Shaft

[gn7]

Separately from the above , centerless grinding is a primarily a high production process , setup and the guides for doing a step grinding from 1" to 7/8 would be a relatively pricey thing and finding a shop to do one-off stuff on a c-less would be difficult.

The 2 shafts I have seen that have reduced diameter, both ends were still 1", and only the area was reduced, with a very generous fillet. So what goes on inbetween is of little concern provided it is reasonably centered between the 2 original areas. I also wouldn't want to bet they were ground, that was an assumption I my part. They could possibly have been reduced on a lath and "polished" Not sure the accuracy of reduction is all the critical. Even if it had to be done by flipping the shaft in the lath due to length, I don't see what it would matter.

The diameter accuracy of the prop shafts is evidently a lot less critical than I would have thought just a few years ago. Because all the shafts I have ever seen were nothing more than mill roll. I have a 17-4 shaft that actually has a very slight depression groove the length of the shaft almost like you would see in welded tubing, and was in service as a multi championship ski boat in the 60s. The groove is kind of handy because you see any twist that might occur in the shaft just by looking at it. Its still pretty much dead straight.