BIG-PLUS® Dual Contact

Basic Concept


BIG-PLUS® spindle system is based on the most currently available standards from MAS403, DIN69871, and ASMEB5.50-1994. Using this system, the taper and face of the machine spindle and tool holder contact simultaneously when clamped with the retention system.

A conventional steep taper tool holder is supported at its maximum taper diameter called the gauge line diameter. A BIG-PLUS® tool holder is supported by the gauge line diameter and flange face diameter which results in higher rigidity and precision than a conventional tool holder can offer.

BIG-PLUS® Dual Contact
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Working Principle


BIG-PLUS® spindle system utilizes elastic deformation of the machine spindle to achieve simultaneous fit of taper and flange face.

Before clamping, the tool holder taper and spindle are in contact with each other to establish good taper fit but face contact does not yet occur. When the spindle's retention knob clamping system is engaged, the tool holder is pulled into the machine's spindle which expands by elastic deformation until the faces of the spindle and tool holder contact each other. This completes the simultaneous fit of the tool holder to spindle.