One of the commonly used metal processing methods: drilling, batch processing of metal parts

1. Definition of drilling

Chinese name: Drilling

English name: drilling

Other names: drilling

Definition: The drilling tool moves relative to the workpiece and performs axial feed motion, and a method of machining holes in the workpiece.

Drilling is one of the most basic hole processing methods. Drilling is often carried out on drilling machines and lathes, but also on boring machines and milling machines. Commonly used drilling machines include bench drilling machines, vertical drilling machines and radial drilling machines.

Second, the characteristics of drilling:

Compared with the turning of the outer circle, it is much more difficult for the drill bit to work locally on the processed surface, thus causing some special problems. For example, the stiffness and strength of the drill bit, chip holding and chip evacuation, guide and cooling and moistening, sliding, etc., its characteristics can be summarized as follows:

1. Bits are easy to deflect

Deviation: refers to the enlargement of the hole diameter caused by the bending of the drill bit during processing, the hole is not round or the axis of the hole is skewed, etc., see Figure 2-6.

Reason: Due to the inaccurate centering of the drill bit, the rigidity and guiding effect of the drill bit are poor, and the drill bit is easy to deflect and bend during cutting.

2. Difficult to evacuate chips

The chip size of the drill hole is wider, and the size of the chip slot is restricted. When it flows out, it violently rubs against the hole wall, and the hole is forced to roll into a spiral shape. The chip and the wall of the hole will cause greater friction, squeeze, roughen and scratch the processed surface, reducing the surface quality. Chips can even block in the chip pocket, jam or break the drill bit, and the tool wears quickly.

In order to improve the chip evacuation condition, the chip separation groove can be ground on the drill bit, and the wide chip can be divided into narrow strips to facilitate chip evacuation. When drilling deep holes, suitable deep hole drilling should be used for processing.

3. High cutting temperature

Because drilling is a semi-closed type cutting, the main cutting edge has a large negative rake angle near the core and the transverse edge. The heat generated during drilling is absorbed by the workpiece, and a large number of high-temperature chips cannot Discharged in time, the cutting fluid is difficult to inject into the cutting area, and the cutting heat is not easily dissipated. The friction between chips, tool and workpiece is very large, so the cutting temperature is high, the tool wear is large, and the amount of drilling and productivity are limited.

4. Low accuracy

The drilling precision is low, the surface is rough, the general processing accuracy is below IT10, the surface roughness Ra value is greater than 12.5mm, and the production efficiency is also low. Therefore, drilling is mainly used for roughing or pre-machining procedures.

Picture: Structure diagram of vertical drilling machine and rocker drilling machine

3. Application of drilling

In single piece and small batch production, small holes (D<13 mm) on small and medium-sized workpieces are usually processed by bench drilling machines, and larger holes (D<50 mm) are usually processed by vertical drilling machines;

The holes on the large and medium-sized workpieces should be processed with a rocker drilling machine, and the holes on the rotating body workpieces should be processed on a lathe.

In batches and mass production, in order to ensure processing accuracy, increase production efficiency and reduce processing costs, drill dies, multi-axis drills or combination machine tools are widely used for hole processing.

For small and medium diameter holes (D<50mm) with high precision and small roughness, it is often necessary to use expansion and reaming for semi-finishing and finishing after drilling.