BT (MAS-BT) is the Japanese MAS 403 tool holder standard — the taper interface between a machine tool spindle and the tool holder, defining the flange diameter, taper angle and pull stud thread. It's the standard fitted to most Japanese-built and Japanese-derived machining centres, distinct from CAT/ISO or HSK systems.
BT30 is the smallest common taper, used on compact and high-speed machining centres. Lower mass and smaller flange diameter suit higher spindle speeds and lighter cutting loads.
BT40 is the most widely used taper on general-purpose machining centres, covering the majority of face milling, end milling and drilling work across a wide rpm range.
BT50 is the largest taper, fitted to heavier machines for high-torque roughing, large-diameter face mills and cuts that demand maximum holder rigidity.
Our Omega toolholders are supplied to G2.5 balance grade and rated for spindle speeds up to 20,000 rpm, in ER collet chuck, end mill holder and other common holder styles across all three tapers.
All held in UK stock, same-day dispatch before 4pm.
