"Oldun" wrote in message news:
I want to make a barrel shaped planter, with 12 straight sides out of 4 by
1 inch timber. The
he4ight of the planter is obviously variable depending on the length the 4
by 1's are cut.

This is the bird's mouth joinery bit that Swingman mentioned
http://www.leevalley.com/wood/page.a...60&cat=1,46168

You might also consider a flute and bead bits.
http://www.leevalley.com/wood/page.a...168,46184&ap=1