A cutting tool whose edge carries the shape to be produced, so the profile is created by plunging the tool straight into the rotating workpiece rather than by moving it along a contour. The geometry lives in the tool. A complex profile therefore takes no longer to cut than a simple one, which is the source of the cycle time advantage in production turning.

When volume is high, cycle time matters and the profile is settled. Form tooling produces the shape in one movement and delivers identical parts without depending on program or tool path accuracy. CNC profiling with a round or button insert is more flexible, needs no special tool and accommodates design changes with a program edit, so it wins on short runs and anything still evolving.

Flat and dovetail tools are ground blanks held in a matching holder, economical to make and suited to simpler profiles. Circular form tools are discs with the profile around the circumference, mounted on an arbor. Because they are resharpened by grinding only the face, the profile is preserved through many regrinds, which makes them the more economical choice over long production runs.

Because the whole width of the profile engages the workpiece at once, so radial cutting force is much higher than for a single-point tool taking a light cut. That force excites vibration in the workpiece, the tool and the machine, and slender parts are particularly susceptible. It is the characteristic failure mode of the class and it is designed around rather than tuned out afterwards.

Maximise rigidity everywhere: short tool overhang, a solid holder, the workpiece gripped close to the cut and supported by tailstock or steady rest if it extends. Reduce speed and feed from what a single-point tool would use. Where the profile is very wide, consider splitting it into stages or using a stepped approach so that less width engages at once.

Yes, and it is a large part of their economics. Circular form tools are ground on the face only, which does not touch the profile, so they can be resharpened many times over a long life. Flat and dovetail tools are also refaced, though with more attention to preserving front clearance. Insert-based tools are not resharpened; the insert is indexed or replaced.

Indexable inserts ground to a defined radius or contour, used either to plunge a simple form or to follow a programmed path and generate a profile. They combine some of the convenience of standard tooling with defined geometry, need no special tool manufacture, and are replaced rather than reground. For simple radii, chamfers and grooves they are usually the practical modern answer.