BBT (MAS 403) Technical Information
BBT holders are taper-and-face contact tool holders designed for higher rigidity, improved runout control, and stable machining performance in face-contact spindle systems.
Higher Rigidity for Demanding Machining
BBT holders provide stronger clamping than standard BT holders because both the taper and flange face contact the spindle. This creates a more rigid spindle-holder connection, improving surface finish, dimensional accuracy, vibration control, and tool life.
Technical Dimensions
| ISO | d | D | D1 | a | b | G | L1 | L2 | L3 | L4 | L5 | L6 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 30 | 12.5 | 31.75 | 46 | 1 | 16.1 | M12 | 48.4 | 21 | 20 | 24 | 7.0 | 16.3 |
| 40 | 17 | 44.45 | 63 | 1 | 16.1 | M16 | 65.4 | 27 | 26 | 32 | 9.0 | 22.6 |
| 50 | 25 | 69.85 | 100 | 1.5 | 25.7 | M24 | 101.8 | 38 | 36.5 | 47 | 13.0 | 35.4 |
Key Features
- More rigid clamping than standard BT holders.
- Higher radial rigidity for stable cutting performance.
- Improved tool life through reduced vibration.
- Better runout accuracy and machining consistency.
- Suitable for high-speed machining applications.
- Strong spindle-holder connection through taper and face contact.
- Supports improved surface finish and dimensional accuracy.
- Recommended for face-contact spindle systems.
Why BBT Performs Better
In a BBT holder, both the taper and the flange face contact the spindle. This dual-contact structure allows the spindle and holder to act as a more unified system, delivering higher radial rigidity, improved dimensional accuracy, better surface finish, and lower vibration at higher speeds.
Primary Applications
- Long-reach axial cutting tools where low TIR is critical.
- Face milling, drilling, reaming, and end milling with radial loads.
- Machining operations requiring improved dynamic stiffness and rigidity.
- CNC machining centers equipped with face-contact spindles and automatic tool changers.
Principle Behind Face-Contact Technology
- Before spindle clamping, the taper interface establishes precise alignment between holder and spindle.
- Once clamped, elastic deformation in the spindle clamping system creates proper face contact between the spindle face and holder flange.
- This simultaneous taper-and-face fit creates a stronger spindle-tool connection for better machining accuracy and longer tool life.
- The system also improves vibration damping, reducing spindle wear and enhancing process stability.
What is the BBT Series Holder?
BBT series holders are manufactured to the BT MAS 403 standard and use taper-and-face contact geometry. Because both the spindle taper and spindle face contact the holder, the spindle and holder perform more like a single rigid unit, resulting in higher rigidity, improved accuracy, and better tool runout control.
Note: For best performance, BBT holders should be used only in properly calibrated face-contact spindle machines.
