BT ER collet chuck is a better choice for drilling and lighter higher speed milling.  It has two forms, Namely form AD and AD/B. 

Both AD and AD/B have standard balances G6.3 15000rpm and G2.5 25000rpm. 

The BT ER Collet Chuck series offers a comprehensive range of tool holders designed to optimize machining operations. With a variety of models available, including BT30 ER20, BT30 ER40, BT40 ER16, BT40 ER20, and BT40 ER40, we provide versatile solutions to meet the diverse needs of machining professionals.

The versatile design of ER collet chucks provides a wide range of machining options. Simply select the right ER collet and ER nut combination from our range.

Taper BT30,BT40,BT50

Hardness: HRC52-58

Balanced G6.3 15000rpm or G2.5 25000rpm 

Material :40Cr or 20CrMnTi

A BT ER Collet Chuck is a type of tool holder used in machining centers, typically for milling operations. It consists of a collet chuck body that is designed to accept ER collets, which are used to hold various types of cutting tools, such as drills, end mills, reamers, and taps.

The BT in BT ER Collet Chuck stands for "Berg Taper," which is a standardized spindle taper commonly used in Japan. The taper is cone-shaped, with a metric thread for easy mounting and removal. ER refers to the type of collet used, which is a spring collet that can be tightened around the shank of a tool for a secure, concentric grip.