Questions about Shopsmith sanding disks

[gaalcom]

I see there are a number of different versions of the Shopsmith 12" disks. So far I've identified a steel (smooth on both sides) and two different aluminum (smooth w/outer ring, ribbed w/outer ring). Might there be a preferred version based on performance such as runout and vibration? Also, arbor size? Looking to buy a used disk (or two) for use on a 5/8" shaft sanding station under construction.

Thanks!

 

[Dumber than lumber]

I think the company made several versions over the years. Their engineers probably made changes and recommendations based on experience, and user feedback.
I have the aluminum one with ribs. Seems to work just fine. Might be harder to get the old pad and glue off the aluminum vs. the steel disk. Don't know.
Also, they make a conical disk, but I have never used one of those.
There is a user Forum on the Shopsmith website and it is quite replete with expertise on all things Shopsmith. The machines take up a bit of space, but they have their place in many home shops.

 

[gaalcom]

Appreciate the reply Dumber than lumber.

Useful info there as I feel myself gravitating towards the aluminum although steel looks to be more widely available in the used market. Still amazes me that after all my searching I've been unable to determine Shopsmith's output shaft or arbor size.