Grooving

Grooving or recessing operations, sometimes also called necking operations, are often done on workpiece shoulders to ensure the correct fit for mating parts. When a thread is required to run the full length of the part to a shoulder, a groove is usually machined to allow full travel of the nut. Grooving the workpiece prior to cylindrical grinding operations allows the grinding wheel to completely grind the workpiece without touching the shoulder.

Face Grooving 
With face grooving operations the tool is fed axially rather than radially toward the end surface of the workpiece. The tool must be adapted to the radial curve of the groove and the blade is therefore curved. When the machine spindle rotates in a counter-clockwise direction, a right-hand version of the tool is used and a left-hand version is used when the machine spindle rotates clockwise.

So that both insert and toolholder fit into the groove, both the outer and inner diameters of the groove must be considered. The diameter measured to the outside of the blade determines the limit for the smallest possible diameter which can be machined, and the diameter measured to the inside of the blade determines the limit for the largest possible groove diameter.

Internal Grooving 
The main problem with internal grooving is chip evacuation. There is a very high risk of chip jamming which can result in tool breakage, especially when machining small diameters. The chips have to be removed from the groove then change direction 90 degrees and pass the side of the toolholder to finally be removed from the hole. Introducing intermittent feed into the program is the best way to obtain short chips.

 Vibration is another common problem associated with internal grooving. Stability is related to the overhang, or how far into the workpiece the groove is to be machined. The risk of vibration is reduced by using the largest toolholder possible. The overhang should not exceed two to two-and-a-half times the diameter. Internal grooving is a critical operation and it is important to choose a tool which optimizes chip evacuation with vibration-free machining.

Grooving tools are usually ground to the dimensions and shape required for a particular job. Most grooving tools are similar in appearance to the cutoff tool, except that the corners are carefully rounded because they reduce the possibility of cracks in the part, especially if the part is to be heat-treated.

Credit:- https://www.americanmachinist.com/cutting-tools/cutting-tool-applications-chapter-6-grooving-and-threading