Guide to CNC Drilling: Chip Breaking and Removal, Hole Precision Improvement and More | CNCLATHING


The drill bit is a widely used machining tool in mechanical manufacturing, especially in the process of drilling holes of specific parts, we have updated the list of drill bit and tap size, you can check it for selecting right drilling tool corresponding to the desired diameter. Today we introduce some characteristics and tips of CNC drilling, involves chip breaking and removal, hole precision improvement and more.

Characteristics of Drilling and Drilling Tool

There are lots of types of drills according to the shapes, materials, structures, and functions, such as high-speed steel drills (twist drills, group drills, flat drills), solid carbide drills, deep drills, and replaceable bits. The drill bit usually has two main cutting edges, the bit cutting the material when rotating, the cutting speed of the drill bit is higher at the outer circle and tends to decrease while towards the center, and the cutting speed of the rotary center of the bit is 0.

Chip Breaking and Removal in CNC Drilling Process

The cutting of the drill bit is carried out in the hole, which is narrow space, the cutting chips must be discharged through the groove of the drill bit, so the chip form or shapes will have a great influence on the performance of the drilling tool. The common chip shapes including flake chip, tubular chip, spiral chip, fan-shaped chips, powder-like chips, etc. The chip control is a key factor of drilling machining, when the chip shapes are inappropriate, some problems will be caused:

1) Thin chips block the cutting edge groove, affect the drilling accuracy, reduce the life of the bit, and even break the tool, like the powder-like chips

2)The long cutting chips around the bit will hinder the operation, causes the bit to break or block the cutting fluid from entering the hole, such as spiral chips

How to Break and Remove the Drilling Chips? - CNC Machining Chips Control

1)Applying one or more methods of increasing feed, intermittent feed, grind cross edge and install chop breaker, to improve the chip breakage and removal.

2)Use specialized chip breaking bit. For example, adding a designed chip breaking edge in the groove of the drill bit can break the long or thick chips and make them easier to remove. Debris can be removed smoothly along the trench without blocking. Therefore, the cutting effect of the new chip breaking drill is much better than that of the traditional drill. In addition, the shorter and smaller chips make cutting fluid flow to the drill tip faster, further improves the heat dissipation effect and cutting performance in the processing.

Hole Precision in CNC Drilling

The hole precision is related to hole size (diameter), position accuracy, coaxiality, roundness, surface roughness, burr, and other factors.

Factors affecting the hole accuracy and precision of the CNC drilling parts:

1) Clamping accuracy and cutting conditions of the bit, such as tool holder, cutting speed, feed rate, cutting fluid, etc;

2) Drill bit size and shape, such as bit length, edge shape, core shape, etc;

3) The shape of the workpiece, such as the opening shape of the hole, the thickness, the clamping state, etc.


The tips for improving the positioning accuracy

1)Drill the central hole first;

2)Use the end milling cutter to mill the hole seat;

3)Select a bit with good cutting performance and rigidity;

4)Reduce the feed rate.

In CNC drilling process, it’s easy to generate burr at the entrance of the hole, can offer deburring and other metal surface treatment, as well as precision CNC drilling services for obtaining the best surface finish for the machined parts.