The new design idea of ​​the machine clamp type drill bit is feasible

The design of the hole machining tool is a complex process that requires coordination of many technical problems. GoranMelin, a drilling product manager at SecoCarboloy (Warren, MI), said, “often a technical problem in one area is solved, and new problems are inevitable on the other hand.” These aspects that require coordination often include tool use. Life, processing accuracy and stability of the process. Tool designers need to constantly find the best solution to the contradictions in these issues.

From the design process of SecoCarboloy's newly-produced PerfoMax machine-type drill bit series, we can see that the above understanding is correct. Through the coordination of many technical problems, the new machine-added drill bit has been designed to greatly expand the processing range.

One such coordination process has been experienced in the design of the new clip-on drill bit: in many of the choices for hole machining tools, the machine clamp drill bit is often a better solution for low cost machining. According to Mr. Melin, the clip-on drill generally designs four cutting edges for the insert, which can be selected for different materials and geometries depending on the material being processed. Normally, the bit body has a service life of 40-50 blades. Therefore, the production cost per drill bit is greatly reduced as compared with the monolithic and welded Drill Bits and the replaceable head carbide drill.

However, in general, users who use a machine-clamp drill bit want a wider machining tolerance, Mr. Melin said. Because high efficiency drill bits are usually designed as an asymmetrical cutting edge. When the clip-on drill uses the structure of two inserts, one insert passes through the center of the cutter and the other extends from the inside to the entire diameter. The blade at the outer diameter of the tool can effectively cut off a large margin due to the high cutting speed. The cutting speed of the blade at the center of the tool is equal to zero, and it cannot participate in the cutting. Therefore, the bit is actually mainly used in the feed direction. Uniform axial cutting force. As a result, since the radial cutting force is insufficient, the frictional resistance is too large, causing bending deformation of the blade body.

“You can feel unstable before the drill enters the entire cut,” Mr. Melin said. “The longer the drill bit, the more unstable the machining state.” Therefore, when using the extended drill bit, the user should reduce the feed rate to 30-50% of the recommended value in the cutting manual at the beginning of the hole machining (about 1 mm). When entering all the cutting, it is processed with the recommended value in the cutting manual. This proposal is indeed very unreasonable. Because in the programming software, the standard cutting amount is generally used, but not for a special feed amount, and the manual reassembly process is additionally used. In addition, the extended drill bit is only used in a very small number of cases, so generally only the cutting amount of the standard drill bit is selected. However, the result of this will reduce the machining accuracy and production efficiency of the parts.

Through analysis and comparison, the twist drill and the solid carbide drill have two cutting edges, which can balance the cutting of the chips in the process, which facilitates the removal of the chips and improves the cutting speed of the drill. The machine clamp type drill bit (as mentioned above) is mainly a cutting edge for cutting (referring to the artificial assembly error caused by mechanical clamping), and only a blade away from the center of the tool can effectively cut off many metals. This will limit the effective elimination of chips and the increase in feed rate. But it does not produce a lot of friction because it does not have a wider blade unique to the twist drill. Therefore, it can be processed at high cutting speed (relative to twist drill). But unfortunately, the use of machine-claw drills has a length of more than 4 times the diameter, especially when selecting a large feed cutting, the deformation of the drill bit becomes a technical problem that needs to be mainly solved. For these reasons, clip-on drills are often used for reaming and semi-finishing where dimensional tolerances are required to be 0.008 inches. Therefore, the use of a clip-on drill can achieve the economical processing desired by the user, but it cannot be processed with higher precision.
In order to overcome the above limitations, SecoCarboloy engineers focused on the following five aspects in the design of the new machine-clamp drill:

In order to prevent bending deformation caused by cutting at high speed and high feed rate, the diameter of the drill body should be increased as much as possible to retain more metal material (for the common gap between the outer diameter of the machine tool and the outer diameter of the drill bit) structure).

The blades are all designed into a rigid rectangular structure, and a deep groove shape of a corresponding size is milled on the drill body. Because the blade is designed to be rounded at 90°, the strength and rigidity are good (the rigidity of the original blade for the clip-on drill is mostly triangular, square, small thickness and mechanical screw clamping, etc.) .

The drill bit is designed with two coolant inlet holes and two slightly inclined flutes with sufficient space. In order to obtain sufficient cooling and effective chip evacuation in the cutting area of ​​the drill bit, it also reduces chipping, prolongs the service life of the drill bit and reduces the surface roughness of the machined parts.

The surface of the drill bit is designed with a highly wear-resistant coating to prevent sticking of the chips to the surface of the body and to extend the life of the drill.

The drill bit is designed to coat a high-hardness, fine-grained substrate with a new coating that can be cut at high cutting speeds and can be used to machine parts made from a variety of materials.

Mr. Melin said that the newly designed clip-on drill has increased rigidity, good cooling and heat dissipation, and greatly improved chip removal performance and cutting stability. Therefore, it is possible to improve production efficiency and part processing accuracy in many processes. These include deep hole parts, machining on less rigid fixtures, and machining of thin-walled parts. In addition to the inherent low cost of processing, it is very popular with users.

The current machine jaw drills are available in sizes ranging from 0.594 to 2.375 inches in diameter and 2 to 5 times in diameter. The drill shank is manufactured to various specifications as standard, including four flat versatile handles for lathes.

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