We start with runout, which is much better for ER Collet Chucks than setscrew holders. Low runout is critical to tool life.

      For best surface finish, we want to maximize the modal or static stiffness. Here, the collet chuck is second only to the shrink fit holders. Where roughing is concerned, the Dynamic Stiffness is important for suppressing chatter, so for maximum material removal rates, we want to maximize Dynamic Stiffness. Here the Collet Chuck also performs pretty darned well, and it is in hogging out lots of material that the hydraulic and milling chuck style holders start to come into their own. The shrink-fit performs poorly because the shrink fit doesn’t dampen the vibrations, it just holds the tool very very tightly. Makes you wonder if it doesn’t make it more likely to ring like a bell when held so tight?