BT shank and JT shank

- Sep 05, 2019-

CNC boring machine spindle bore is usually ISO 7:24 NO.50, divided into BT50 and JT50, the corresponding BT shank and JT shank.

The taper of both shanks are the same, namely 7:24, but the manufacturing standard is different. The BT shank uses the Japanese standard MAS-403 and the JT shank uses the German standard DIN 69871. The difference between BT shank and JT shank is that the gripping part of manipulator is different from the rivet, BT shank flange thickness is larger, Manipulator clamping groove near the tools side, the depth of the two end key groove is the same and doesn’t mill through; JT shank flange thickness is small, there is a positioning notch for a tool, the depth of the two end key groove is different and mill through.

There is also a manufacturing standard JISB6339 for BT shank, Although the Japanese standard JISB6339 has replaced the MAS-403 standard of the Japanese working machinery industry association, it has little impact on the use because its main external dimensions are the same, Therefore, many tool manufacturers' samples are still labeled with MAS-403 standard code, but not JISB6339.

However, it should be noted that the two standards used by the rivet are different.



The rivet of various specifications correspond to the corresponding specifications of the shank and the corresponding specifications of the rivet jaw. There are two standards for BT type shank rivets, namely MAS403 standard and JIS B 6339 standard. MAS403 rivets have Ⅰ type and Ⅱ type two kinds, Ⅰ type rivet taut surface Angle of 30°, the tension device for not strip steel ball; Type Ⅱ rivet taut face Angle 45°, tension device for strip steel ball. The head length of these two kinds of rivets is smaller than that of JIS B 6339, and the neck length is longer. JIS B 6339 taut plane Angle of taut nail is only 15°, used for taut device without steel ball.


JT type shank rivet, its standard is DIN69872.The inclined Angle of JT tensioning plane is 15°, which is used for tensioning device without steel ball.


If you change the tool manually instead of using the manipulator, the BT and JT shanks can be used in general, Using: BT nail +JT shank for BT machine tool or JT nail +BT shank for JT machine tool .In general, there is no problem when using.

If using the manipulator to change the toos automatically, then the two shanks can not be mixed.