just had a conversation with a member concerning this,
his response was the same, sand at slower/slowest lathe speed
As I just found out, higher speeds equal higher heat, and the distinct possibility of heat cracks in the wood.
Even tho I kept sanding motion sweeping, and hand nor sandpaper got even remotely warm, the wood did in fact develop heat cracks.
So now, I too have to agree about using the slower speed
You got some good advice, Jerry......
Aside from heat checking, another drawback from heat is burning (slightly discoloring) the wood. This may not be apparent until after you apply a finish......and, there it is! Very disappointing to go all the way back to re-sand the burn, or discoloring completely away. I haven't seen any burning for quite a long time, but it was a problem for me back in the 1980's. Burning (or discoloring) the wood is pretty easy to do with powered sanding, but normally not much of a problem with sandpaper held by hand against spinning wood, until you get into the higher grits. As you already know, keeping the sanding motion fluid, and not concentrated on any one spot for long, is key to keeping heat at a minimum.
Most all my sanding is done with a powered angle sander (Sioux or Milwaukee) variable speed up to 1200rpm, using 2" and 3" flexible discs. The lathe is generally around 300rpm. When I do random orbital sanding, it's usually around 25rpm, using 400, or 600 grit.
Powered sanding is usually done up to 180 grit, and done by hand for higher grits than that. Occasionally, powered sanding is done at 220 grit, but not very often. (To clarify, when I say "by hand", I mean folded sandpaper held in your hand with lathe spinning at around 300rpm.)
All speeds mentioned are approximate, and each specific application (or individual's choice) may vary somewhat........
I usually don't sand completely by hand (lathe turned off), except when I need to deal with one little spot that needs work.
ooc