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

Usually, when processing high-precision parts, the slow-moving wire cutting machine is widely used.

1. The definition of drilling

Chinese name: Drilling

English name: drilling

Other names: drilling

Definition: The method of drilling a hole in the workpiece by moving the drilling tool relative to the workpiece and making an axial feed movement.

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 are bench drilling machines, vertical drilling machines and radial drilling machines.

2. The characteristics of drilling:

Compared with turning the outer circle, drilling is much more difficult to work on the machined surface, which causes some special problems. For example, the rigidity and strength of the drill bit, chip holding and chip removal, guiding and cooling and smoothing, etc., its characteristics can be summarized as follows:

1. The bit is easy to lead deviation

Lead deviation: refers to the enlargement of the hole diameter, the out-of-round hole or the skewed axis of the hole caused by the bending of the drill bit during processing, as shown in Figure 2-6.

Reason: Due to the inaccurate centering of the chisel edge of the drill, the rigidity and guiding effect of the drill are poor, and the drill is easy to shift and bend when cutting.

2. Difficult chip removal

The chips of the drilling hole are wide, and the size of the chip flute is restricted. When it flows out, it rubs against the hole wall violently, and the hole is forced to roll into a spiral shape. Make the chips and the hole wall have a greater friction, squeeze, roughen and scratch the processed surface, reducing the surface quality. Chips may even block in the chip pockets, jam or break the drill, and the tool wears quickly.

In order to improve the chip removal conditions, a chip groove can be ground on the drill bit to divide the wide chips into narrow strips to facilitate chip removal. When drilling deep holes, suitable deep hole drills should be used for processing.

3. High cutting temperature

Since drilling is a semi-enclosed cutting, there are large negative rake angles on the main cutting edge near the core and the chisel edge. The heat generated during drilling is absorbed by the workpiece a lot, and a large amount of high-temperature chips cannot Discharge in time, cutting fluid is difficult to inject into the cutting area, cutting heat is not easy to spread. The friction between the chips, the tool and the workpiece is very high, so the cutting temperature is high, the tool wear is large, and the amount of drilling and the increase in productivity are limited.

4. Low accuracy

The precision of drilling is low, the surface is rougher, 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-processing.

Figure: Structure diagram of vertical drilling machine and radial drilling machine

Three, the 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 by a radial drilling machine, and the holes on the rotary workpiece should be processed on a lathe.

In batch and mass production, in order to ensure processing accuracy, improve production efficiency and reduce processing costs, drilling dies, multi-axis drills or modular machine tools are widely used for hole processing.

Small and medium diameter holes (D<50mm) with high precision and small roughness often need to be expanded and reamed for semi-finishing and finishing after drilling.