BT denotes taper shanks for machining center machine tools
(with robotic clamping slot) manufactured in accordance with Japanese standard MAS403;
universal shanks with 7:24 taper. st denotes taper shanks for CNC machine tools
(without robotic clamping slot) manufactured in accordance with GB3837.
General purpose toolholders with a 7:24 taper are usually available in five standards and specifications,
namely NT (conventional), DIN 69871 (German standard), IS07388/1 (international standard),
MAS BT (Japanese standard) and ANSI/ASME (American standard).

The NT type toolholder, DIN 2080, is used on conventional machines to tighten the toolholder by means of a drawbar,
also known as ST in China; the other four types of toolholders are used on machining centers to tighten the toolholder
by means of a spigot at the end of the toolholder.

MAS BT type (BT for short) The BT type is a Japanese standard, and the mounting dimensions are completely different
from those of DIN 69871, IS0 7388/1 and ANSI, and cannot be exchanged. The symmetrical construction of the
BT type shank gives it better high-speed stability than the other three shanks.