Compared with external surface machining, the conditions for precision CNC machining of holes are much worse, and machining holes is more difficult than machining external circles. This is because:

1) The size of the tool used for precision CNC machining of the hole is limited by the size of the hole to be machined, the rigidity is poor, and it is prone to bending deformation and vibration;

2) When machining a hole with a fixed-size tool, the size of the precision CNC machining hole often directly depends on the corresponding size of the tool, and the manufacturing error and wear of the tool will directly affect the machining accuracy of the hole;

3) When CNC machining holes, the cutting area is inside the workpiece, the chip removal and heat dissipation conditions are poor, and the machining accuracy and surface quality are not easy to control.





1. Drilling and reaming
(1) Drilling is the first process of CNC machining holes on solid materials, and the diameter of the holes is generally less than 80mm. There are two ways of drilling: one is the rotation of the drill; the other is the rotation of the workpiece.

(2) Reaming
Reaming is the further processing of holes that have been drilled, cast or forged with a reaming drill to expand the aperture and improve the processing quality of the holes. Final machining of less demanding holes.


2. Reaming
Reaming is one of the finishing methods of holes and is widely used in production. For smaller holes, reaming is a more economical and practical precision machining method than internal grinding and fine boring.


3. Boring
Boring is a precision CNC machining method that uses a cutting tool to enlarge a prefabricated hole. The boring work can be carried out on a boring machine or a lathe.


4. Honing holes
Honing is a method of finishing a hole with a honing head with a grinding stick (whitstone). During honing, the workpiece is fixed, and the honing head is driven by the spindle of the machine to rotate and make a reciprocating linear motion. In the honing process, the grinding bar acts on the surface of the workpiece with a certain pressure, and cuts a very thin layer of material from the surface of the workpiece, and the cutting trajectory is a crossed mesh. In order to make the movement track of the abrasive grains of the sand bar not repeat, the revolutions per minute of the rotary motion of the honing head and the number of reciprocating strokes per minute of the honing head should be prime numbers of each other.


5. Pull hole
Hole broaching is a highly productive finishing method that is performed on a broaching machine with a special broach. There are two types of broaching bed: horizontal broaching bed and vertical broaching bed, and the horizontal broaching bed Z is the most common.