Like all palms, it is composed of dense fibers surrounded by a matrix of fairly soft open cells, which when alive, transport liquids via osmosis and support the trees respiratory processes. When dried this matrix is very soft, often crumbly, and the fibers become extremely hard and tend to splinter.
To turn you definitely need to reinforce the matrix with thin ca, and be sure to cut the fibers so that the cut is "pulling" them against the longest area of support. Not sure quite how to explain that, but you don't want to "push" the fibers, or they tend to pop out. After I get rounded, I usually tend to switch to the dreaded 80 grit gouge for shaping.