Insert Template Bit 1/2″ Dia. x 1/4″ shank 30mm cut x 80mm length. flutes. Template bits also known as Pattern bits or Straight Bits with Centre Ball Bearing are used in woodworking to replicate letters, shapes or designs by means of copying an overlaid shape onto the desired material. The Ball Bearing guide will ride along the Template, and the carbide teeth will cut into the material at the exact diameter of the bearing, hereby copying the design flush with the bearing’s diameter.