Showa Tool Co., is a world-wide authorized and certified manufacturer of Big-Plus™ Tooling. The Showa Big-Plus™ concept combines the rigidity and stability of simultaneous fit with high precision toolholders such as Micron Milling Chucks, Micron Mold Chucks, and RSC Collet Chucks.

The Big-Plus™ tooling system is modeled after ANSI and JIS standard tooling allowing customers to utilize standard toolholders (i.e. tapholders) in the same machine, unlike other specialized tapers.  The simultaneous fit tooling system provides added stability and rigidity by not only contacting the taper of the toolholder like conventional tapered tooling, but also on the face of the flange. A conventional step taper is supported on a reference diameter named the gauge face.  Whereas a Big-Plus™ toolholder is supported on the flange face, which provides higher rigidity and precision than a conventional toolholder.   The dual face also provides stability during high speed machining operations by preventing axial movement of the toolholder.  

Big-Plus™ spindle system utilizes elastic deformation of the machine tool spindle, creating simultaneous fit of taper and flange.  Before clamping, although tapers are fit, faces have small clearance and are not fit at this point. When a tool holder is pulled in by a clamping mechanism, a machine spindle expands by elastic deformation and the faces are fit, which completes simultaneous fit between taper and face.

Big-Plus™ tooling is available in BBT30, BBT40, BCV40 and BCV50 tapers in Micron Milling Chucks, Micron Mold Chucks, RSC Precision Collet Chucks, Shell Mill Holders and End Mill Holders.

Big Plus as a registered trade mark of Big Daishowa Seiki Co. Ltd. Japan. Showa Tool Co. Ltd Japan is officially licensed to produce Big Plus tooling under the strict licensing and quality control agreement of Big Daishowa Seiki Co. Ltd Japan.