If a drill is used to process the cross holes of steel parts, it is a headache for many tool manufacturers and engineers. After R&D, the Antimony Mast Tool finally solved this problem, providing an optimized process plan and a special drill for such processing.
For the drilling of cross holes of steel parts, the impact at the broken hole causes uneven stress on the drill bit, which is prone to blade breakage, tool breakage and rapid wear. As a result, tool users have high cost and low efficiency, and the quality is difficult to control stably. A well-known domestic axle manufacturer has been puzzled by this problem for a long time. Product working conditions and processing conditions are as follows:
The material to be machined is 50 # steel, HRC28-32, with holes drilled on the blank surface, roughness of 3.2, one piece with two holes, vertical CNC machining center, machine tool with internal cooling, hydraulic fixture, hydraulic tool handle.
The hole depth, diameter and hole breaking are shown in Figure 1:
Fig. 1 Cross hole size of axle pin hole
At present, there are many well-known brands of suppliers providing solutions and tools for this axle manufacturer, but the effect is not satisfactory. The following situations are summarized:
Scheme 1: The world's top brand replaceable drill bit or U-drill is used. When the drill bit is processed to the hole breaking point, the interchangeable 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 used to complete the drilling directly in one sequence. The practice has proved that the machining is unstable, the service life is low, the tool is often broken, and the straightness and roughness are difficult to guarantee.
Scheme 3: Adopt the world's top brand of cemented carbide internal cooling flat bottom drilling. Practice has proved that the efficiency is low, the tool wear is fast, and frequent tool change is required.
Scheme 4: Increase the pilot drill, use the world's top brand drill bit, feed in sections, and reduce the speed at the half hole, so that the size and requirements of the processed product are still stable, but the drill bit is still rapidly worn, and the number of regrinding is only one or two times. For such a low life, the customer's cost is also very high.
Obviously, the above schemes have obvious shortcomings. The scheme provided by Sima Tools has achieved the following four points:
1. The drill bit is normally worn, the processing condition is stable, and the hole size and all requirements can be continuously guaranteed;
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. The number of regrinding can be 5-7, and the cost reduction is also considerable.
After several improvements in bit design and processing technology, the above effects have been achieved. First of all, the drill bit is designed ingeniously, especially the transverse edge form, tip protection and negative chamfer design of the groove are just right, and the edge passivation further improves the wear resistance, as shown in Figure 2.
Fig. 2 Perfect groove, edge and edge treatment
Secondly, through many tests, we have summarized a reasonable cutting scheme - guide drill+hole breaking drill, as follows:
Process 1: guide the drilling to a certain depth to guide the hole breaking drill.
Procedure 2: ￠ 15 hole breaking drill processing, Vc=70M/min, feed is divided into three sections, and F=0.25mm/r is used when processing to 30MM depth. When processing to 60MM depth (i.e. hole breaking processing section), the feed speed is reduced by F=0.1mm/r, and then it is restored to F=0.25mm/r after the hole breaking processing, until the whole hole processing is completed.
