Most JT handles have internal cooling channels, which support internal cooling of the spindle center or (and) internal cooling of the spindle end face. The main structure is shown in the figure below. BT handle is a Japanese standard. The shoulder size is larger than that of JT, so the tool weight is increased. There is positioning on the 180-degree circumference, and there is no positioning notch that is unfavorable to dynamic balance. Most BT handles do not have internal cooling channels. Some BT handles with internal cooling channels can be provided, but because the neck of the rivet of the BT handle (especially BT40 and below) is thin, adding a central internal cooling channel may cause the rivet to be pulled off and the tool handle to fall off. The main structure is shown in the figure below. In principle, there is not much difference. But in actual use, it must be distinguished and not confused.

     BT machine tools cannot use JT tool holders, and JT machine tools cannot use BT tool holders. Most European machine tools are configured as JT, such as DIN69871. Most European JTs can be equipped with center coolant or spindle end coolant. Most Japanese, Korean, and Taiwanese machine tools are configured as BT. BT tool holders may not have coolant because the neck of the rivet is thin. If the rivet is equipped with a coolant hole, the cross-sectional area may be too small and the strength will be insufficient.