Arch
I have turned 18" platters on my Craftsman and the minimum speed is 400 rpm.
I think I was turning about 800 but I no longer know for sure. My largest on
the Record bowl lathe was 18" and its lowest speed is 575 rpm. Record says
you can turn up to 24" and used to say up to 36", I believe. I am neither
24" stupid nor certainly not 36" crazy. :-)

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God bless and safe turning
Darrell Feltmate
Truro, NS Canada
www.aroundthewoods.com