Cutting tool for boring, machining apparatus for boring and method for boring

A cutting tool for boring that is attached to a machining apparatus and used for performing cutting of a hole on a large-diameter side of a stepped hole of a workpiece,

• the machining apparatus comprising a pair of left and right machining units arranged opposing each other so as to sandwich a workpiece,
• the cutting tool for boring being provided in a set of two which are attached to the pair of left and right machining units respectively,
• each of the cutting tools for boring in the set of two comprising:
• a shaft part;
• a cutting blade laterally protruding from the respective shaft parts;
• and
• an abutment surface that is formed at a tip of the respective shaft parts and that is for causing the tips of the respective shaft parts to butt against each other,
• wherein:
• each of the cutting tools for boring performs the cutting while the two cutting tools for boring rotate integrally around a center line of the shaft part in a coupled state in which the tips of the respective cutting tools for boring are butted together.