In article 1130892173.221257.51950
@g43g2000cwa.googlegroups.com,
says...
Cast iron is much stiffer than steel, so it won't allow the
chuck to twist out of axis when taking heavier cuts. In this case, the
steel plate will be such a small diameter and rather thick that it
might work.


Cast iron is considerably *less* stiff than steel. Its
modulus of elasticity, depending on the exact alloy, varies
from around 12 million psi(common gray cast iron) to 25
million psi(malleable cast iron). Steel is 30 million psi,
aluminum about 10.

Ned Simmons