Do a search for "hollow spiral candlestick" or "hollow spiral light".
One example, part 1 of 5 videos.
A very recent post by Bill Wyko using similar concept. See his post #33
Edit - additional link
Sears used to sell a Router Crafter which was a way to create spirals on the spindle. I have one. Not liking it. A fellow created a site showing the capabilities. One of the items was a hollow spiral.
Last edited by Dave Paine; 09-05-2013 at 12:40 PM.
Reason: Added link