Deep hole machining can be classified into seven categories based on the machining method:

1.Solid Drilling: This refers to the deep hole drilling method of removing excess material from solid materials using drilling tools. Solid deep hole drilling is considered a primary machining process.

2.Boring: This is a further deep hole machining process for forged, cast, or drilled deep holes. Boring can increase the diameter of the deep hole, improve accuracy, and reduce surface roughness. Deep hole boring can be divided into push boring and pull boring.

3.Hobbing: This is a machining method that forms a cylindrical hole in solid materials by removing the entire mandrel.

4.Reaming: This is a drilling method that enlarges the diameter of an existing (cast, forged, rolled) hole in a workpiece to the required size. Reaming drilling is a primary machining process.

5.Countersinking: This is a cutting method that uses a countersink to remove a thin layer of metal from the wall of an already machined hole, in order to obtain an accurate hole diameter and geometric shape, as well as a lower surface roughness. Countersinking is usually performed after drilling, reaming, or boring, and is considered a semi-finish machining process.

6.Honing: This is a grinding process for holes that have been precision bored, which can significantly improve the surface roughness (Ra) and dimensional accuracy. Honing is a finish machining process.

7.Rolling: This is a machining method that applies a certain amount of pressure to the surface of a workpiece through a rolling tool after precision boring, causing plastic deformation. It can achieve both smoothing and strengthening effects simultaneously.

Note: Currently, there are specialized cutting tools that can combine multiple machining methods into one. Examples include combined rolling and boring heads, step drills, etc.