[ATM] Polihing turntable bearings

["Don Clement" <don_clement@charter.net>]

The bearings for a polishing machine turntable should not add a periodic component. The regular arraignment of the balls in a ball bearing race can add a periodic component to the surface finish. One way to make a bearing for a polishing machine turntable would be to use an air bearing. Air bearings are expensive and require a clean well-filtered air source. Before digital audio CDs there was a developed technology for high end audio vinyl playback. Vinyl playback turntables are highly sensitive to periodic signals. One bearing support was the "inverted bearing" design where a steel shaft rode in an oil bath with a single ball bearing at the bottom. The steel shaft was not polished but finished in a rough surface to hold the oil on its surface. A picture of the turntable platter with steel shaft for my vintage Marantz SLT turntable, shows the steel shaft with helical grooves to distribute the oil. See:

http://i72.photobucket.com/albums/i163/miltons_stuff/marantzSLT.jpg 

A more recent high end turntable is the SOTA that uses a sapphire thrust plate polished to one wave and a ceramic ball bearing riding in a Turcite sleeve. See:

http://www.sotaturntables.com/Sound%20Engineering.htm  
_______________________________________________
ATM mailing list http://www.atmlist.net/