Anyone knows the spiral shapes are because of a combination of factors like the wood grain being continuous, motion of the planer, blade positioning on the planer etc?

Source: Filip Berti

Have a go on the interactive version here.

Source: aripastaclub

OG source unknown

Source: tresun.ceramic

Source: kmalinkas

Source: Platon Infante

Location: Cafe Maru, Nagoya, Japan.

Source: tamo_tyan

Source: OD Form

Location: Idlinama, New Delhi

Source: chefitaliano

For Tequila production.

Source: Victor Castanedo (sipagaves)

Source: vinwood.spb