Introduction of taper of BT40 and BT50 high speed tool holder

August 07, 2019

In general, the most commonly used tool holder is BT tool holder. When the taper of BT tool holder is 7:24 And the speed is about 10,000 r/min, the tool holder-spindle system does not appear obvious deformation. But when the spindle rises from 10,000 r/min to 40,000 r/min, due to centrifugal force, the end of the spindle system will appear larger deformation, and its diameter jump from 0.2 M. It increased to about 2.8 M. Clearance between tool holder and taper hole of spindle will appear obviously, which seriously affects cutting characteristics of tool, so BT tool holder can not be used in high speed cutting generally.

There are several national standards for tool holders of machining centers. BT is Japanese standard (MAS403), taper is 7:24, size specifications are 60, 50, 40, 30.
"40, 50" represents the diameter of taper cross section of the tool handle.
BT40: The tolerance of 63mm diameter is - 0.05 to 0; the diameter of trapezoidal groove bottom is 53mm; the width of trapezoidal groove top is 10 mm tolerance is 0 to + 0.1; the angle of trapezoidal groove is - 15'to 0; the distance between the center of trapezoidal groove and the end of spindle (the big end of tool handle cone) is 16.6 mm tolerance is positive and negative 0.1.

BT50: The tolerance of 100mm diameter is - 0.05 to 0; the diameter of trapezoidal groove bottom is 85mm; the width of trapezoidal groove top is 0 to + 0.1; the angle of trapezoidal groove is - 15'to 0; the distance between the center of trapezoidal groove and the end of spindle (the big end point of tool handle cone) is 23.2mm and the tolerance is positive and negative 0.1.

tool holder