This American National Standard defines terms for certain basic features of single-point cutting tools. It deals with those features which are necessary to define the geometry of the cutting part. The first main section (section 4) defines general terms applicable to single-point tools, including surfaces on the workpiece, tool elements certain specific dimensions and tool and workpiece motions. In the subsequent sections two systems of reference planes are defined with the aid of which so-called too angles and working angles are defined. One system of reference planes is the tool-in-hand system ; this is used to define the geometry of the tool so that it can be manufactured and measured. The other system of reference planes, the too-in-use system , is required to define the effective geometry of the tool when it is actually performing a cutting operation.