What is CNC boring? CNC machining of boring refers to the expansion or refinement of the original hole on the workpiece. CNC-machined boring is characterized by correcting the eccentricity of the lower hole, obtaining precise hole positions, and obtaining high-precision roundness, cylindrical and surface finish. Therefore, boring is often used in the final process.

Compared with other machining, CNC machining is a kind of difficult machining. It only depends on adjusting a blade (or blade seat) to process micron holes like H₇ and H₆.

CNC-machined boring

What are the characteristics of CNC boring?

1. Tool rotation
CNC machining is different from lathe machining. Due to the rotation of the tool during machining of the machining center, it is difficult to grasp the condition of the tool tip in time to adjust the amount of feed during machining. It is also difficult to be able to change the machining diameter just by adjusting the CNC button like a CNC lathe. This has become a big difficulty in completely automated processing. It is also because the machining center does not have the automatic machining diameter adjustment function (except for the U-axis function), the boring tool needs to have a fine adjustment mechanism or an automatic compensation function, especially in the fine boring according to the tolerance requirements and sometimes need to be in the micron level. Adjustment.

In addition, when the machining center is boring, the outflow direction of the chips is constantly changing, so the cooling of the tool tip, the workpiece and the discharge of the chips are much more difficult than in the lathe machining. Especially when a vertical machining center is used for rough boring of steel blind holes, this problem has not been completely solved so far.

CNC-machined boring

2. Flick knife
The most common and most troublesome problem in boring is the bullet knife. The reasons for the bullet knife on the machining center are as follows:

① Rigidity of the tool system: including the rigidity of the toolholder, boring bar, boring head and their intermediate connecting parts. Because it is cantilever machining, the rigidity of the tool is particularly important when machining small holes, deep holes and hard workpieces.
dynamic balance of the tool system: relative to the axis of rotation of the tool system, if the tool itself has an unbalanced quality, chattering occurs due to the effect of the unbalanced centrifugal force during rotation. Especially in high-speed machining, the dynamic balance of the tool has a great impact.
the workpiece itself or the placement rigidity of the workpiece: For example, some small and thin parts are not sufficiently rigid due to their own rigidity, or due to the shape of the workpiece, etc., it is impossible to use a reasonable jig for adequate placement.
the shape of the tip of the blade: the cutting resistance caused by the difference of the blade’s rake angle, escape angle, tool tip radius, and chip breaker shape is also different.