Solution for cross hole breaking of steel parts

If the cross hole processing of steel parts is completed by drill, it is a headache for many tool manufacturers and engineers. After research and development, antimar tool has finally solved this problem and provided an optimized process scheme and special drill bit for this kind of processing.

In the drilling process of cross holes of steel parts, the impact at the broken hole leads to uneven stress on the bit, and the bit is prone to edge collapse, knife breakage and rapid wear. Therefore, tool users have high cost, low efficiency, and it is difficult to stably control the quality. A well-known axle manufacturer in China has been puzzled by this problem for a long time. Product working conditions and processing conditions are as follows:

The material to be processed is 50# steel, hrc28-32, drilled on the blank surface, roughness 3.2, one piece with two holes, vertical CNC machining center, machine tool with internal cooling, hydraulic fixture and hydraulic tool handle.

The hole depth, diameter and hole breaking are shown in Figure 1:

At present, there are many well-known brands of suppliers who provide solutions and cutting tools for this axle manufacturer, but the effect is not ideal. The summary is as follows:

Scheme 1: adopt the world’s top brand replaceable bit or u-drill. When the bit is processed to the hole, the replaceable head will often fall off. This scheme is unstable.

Scheme 2: the standard cemented carbide internal cooling bit of the world’s top brand is directly completed in one sequence. Practice has proved that the processing is unstable, the service life is low, the cutter is often broken, and the straightness and roughness are difficult to guarantee.

Scheme 3: the world’s top brand cemented carbide internal cooling flat bottom drill is used for processing. Practice has proved that the efficiency is low, the tool is worn quickly, and the tool needs to be changed frequently.

Scheme 4: increase the guide drill, adopt the drill bit of the world’s top brand, feed in sections, and reduce the speed at the half hole. In this way, the size and requirements of the processed products are still stable, but the drill bit still wears rapidly, and the re grinding times of the drill bit are only one or two times. For such a low life, the cost of customers is also very high.

Obviously, the above schemes have obvious deficiencies. However, the scheme provided by antimar tool achieves the following four points:

1. The drill bit is normally worn and the processing condition is stable, which can continuously ensure the size and requirements of the hole;

2. The service life is stable at 210-230 pieces (38-40m), which is twice the best use of imported brand bits mentioned above;

3. Increase efficiency by 1 / 3;

4. Regrinding times can be 5-7 times, and the cost can be reduced significantly.

The above results have been achieved through many improvements in bit design and processing technology. First of all, the design of the drill bit is ingenious, especially the form of the transverse edge, the protection of the tip and the negative chamfering design of the groove are just right, and the passivation of the edge further improves the wear resistance, as shown in Figure 2.

Secondly, through many tests, we have summarized a reasonable cutting scheme – guided drill + hole breaking drill, which is detailed as follows:

Process 1: guide the drill to a certain depth to guide the hole breaking drill.

Process 2: ￠ 15 hole breaking drill processing, VC = 70m / min, the feed is divided into three sections, f = 0.25mm/r is used when processing to 30mm depth, f = 0.1mm/r is reduced when processing to 60mm depth (i.e. hole breaking processing section), and then it is restored to f = 0.25mm/r after hole breaking processing until the whole hole processing is completed.