I have a dyna 4400 still happily working under SKIP control. My tool holding is via ER collets. Largest size I have is ER 32 (20 mm capacity). I have a lot of 1 inch shank HSS cutters and even a tool and cutter grinder to keep them sharp and could easily buy a BT30 ER 40 to suit the mill and these larger tools. However, I have some concerns that this larger tooling with its longer collet chuck hangout might be a bit much for the BT 30. Has anyone out there experience with this or any thoughts..... Martin