Re: Type of steel for internal structure of eg frame?
Choice partly depends on degree of machining after casting.
Using precision ground stock usually means they are trying to avoid machining after making the EG casting.
Hard to align and keep aligned to the necessary tolerances in a wood / non precision mold. So this may be a waste of time.
Hot rolled stock is a better choice than cold rolled as the material has less stress. Stress will relieve when machined, potentially resulting in deformation.
(Or you can get your stock stress relieved before EG casting. Cannot use thermal stress relief after epoxy).
7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)