New development of drilling technology

Although there are many different rotary cutting tools that can machine holes, drilling is still the main method of hole machining. New bit designs using new materials, new coatings and reasonable geometries are emerging today; bit materials are being used in more advanced materials such as cobalt, tungsten carbide and nanocrystalline cemented carbide. The new bit coating enables the bit design to provide a more efficient bit geometry. Among the bit materials and coatings, microcrystalline hard alloy materials and the latest physical vapor deposition (PVD) coatings have great potential.

In drilling, it is important to choose the right drill. Drilling a hole with a diameter of 51 to 76 mm or more requires a relatively high power. Usually, the drilling process must be completed in two processes. Since the large-diameter hole consumes a large amount of power, machining with only one bit is difficult to achieve. . In addition to the aperture size, other factors of drilling, such as machining materials, part shape, etc., are also key factors for drilling. Some materials are easier to machine than others; it is not difficult to drill holes in larger pieces of steel, but it is more difficult to drill holes in an area with complex shapes and limited space.

Drills with replaceable inserts are ideal for the machining of through-holes. For precision hole machining, solid carbide drills are used. Brazed drills and drills with hard alloys are easily removed in drilled holes. use. Replaceable insert bits not only save the cost of expensive tool re-grinding associated with solid carbide and steel drills, but also allow a variety of interchangeable inserts to allow operators to quickly change the geometry of the drill insert to improve the cutting performance of the drill. .

New Bit Design and Manufacturing Technology

The quick-change drill has the processing flexibility, and the user can maximize the performance of the drill by changing the sharpening method of the drill, the back face taper and the geometry of the drill. For example, for processing some hard materials (such as stainless steel and high-temperature alloys), the drill should have sharper cutting edges and larger flank taper. If you want to reduce the cutting force, make the tool drilling more smooth, smoother chip removal, you can optimize the bit performance by changing the geometry of the drill bit.

According to the cutting performance requirements of the drill, the material composition inside the mixed cemented carbide drill can be changed. Sandvik's dual carbide drills combine the properties of two different types of carbides. In theory, the cutting speed is zero at the center of the bit, and the strong, cobalt-rich carbide can withstand vibrations caused by very low cutting speeds. As the cutting speed is reduced, the chips may be welded to the cutting edge. The drill should have sufficient rigidity and lubricity, and the new drill can get good lubrication performance through the coating. The peripheral edge of the drill bit rotates at a very high cutting speed. At this time, the drill bit requires a hard, high-strength hard alloy and an abrasion-resistant coating. Sandvik often uses titanium nitride (TiAIN) and titanium carbonitride (TiCN) as the drill bit coating. In order to further improve the lubrication characteristics, other coating materials may also be added.

Submicron grained carbide materials have broad application prospects in rough and rough milling. In recent years, cemented carbide materials and cemented carbide blade manufacturers have entered the field of development of smaller grain cemented carbide materials. A new process enables manufacturers to obtain sub-micron carbide grains that combine the high tensile strength of hard alloy high-speed steel with cemented carbide. In drilling, no matter how fast the drill bit rotates, the cutting speed at the tip of the drill bit is almost zero. When processing hard materials, the drill bit may be crushed, and using a microcrystalline carbide drill bit can avoid this danger.

Before Carbide sintering, Iscar produces submicron grained carbide by adding various additives to the cemented carbide, usually during the metallurgical process of heating and sintering the cemented carbide to form the final shape. The size tends to grow. This submicron grained carbide is a rigid material similar to high-speed steel, hard and hard alloy. It can use very high cutting speeds and its tool life is The original tool life of 8 to 10 times.

With the advent of advanced coatings, some tool manufacturers have developed drills with more reasonable geometry, such as dry machining drills. Correctly determining the proper geometry of the drill bit depends on the size and specific use of the drill bit used. The large-scale processing on advanced CNC machining equipment generally requires higher cutting speeds and feeds, so the drill requires a more reasonable cutting edge geometry.

Advanced bit holder system

For a satisfactory machining result, the performance of the fixture holding the drill is critical. If the drill jig does not reach the required rigidity, effective cutting cannot be performed even if the power to drive the drill bit is obtained. Advanced drilling fixtures can achieve very small drilling tolerances, although most of the drilling process does not require too high accuracy, but there are still some drilling machining accuracy requirements are still high. Recently, Bilz/RMT Tool Company and TM Smith Tool International have introduced a new tool holder system for precision drilling - the Thermo-Grip tool holder, which is a new type of hot clamping tool system, Thermo - Grip tool holder does not use clamping screws to hold the tool holder, nor use nuts and washers to fix the tool. Since there is no tightening screw on one side of the fixture, it will not cause vibration, so the tool and fixture have good from the beginning. Dynamic balancing allows drilling to perform high-speed machining in equilibrium. The hole of the Thermo-Grip jig is slightly smaller than the cutting tool. The front end of the jig is heated by an induction coil. The thermal expansion expands the hole of the jig and inserts the cutting tool. When the jig is cooled, sufficient cooling can be generated under the effect of cooling and compressing the tool holder. Tool holding force.

TM Smith Tool Company developed two new drilling tool systems: HSK and near-center drilling system. According to the company's forecast, the two systems are rated for coolant pressure of 6895 kPa (actually up to 8274 kPa).

Briggs & Stratton used the advantages of the traditional ideal conical toolholder design to develop a close-tolerance tool holding system. The system uses an ideal conical nose with 6 spherical holes in the center of the tool holder to hold the tool system on the spindle. The user can choose to use a hole plug that is screwed on the back of the tool. The hole plug is connected to the spindle body to separate the coolant at the rear of the tool.

In order to increase the cutting speed and extend the tool life, many users have applied the HSK short taper shank, high-speed spindle, and small diamond inserts to actual machining. The use of a pointed PCD tool allows longer tool life, reduces the number of tool changes, and maximizes the number of holes per tool. HSK hollow short taper shank enables tool mounting tolerances up to 0.00013mm or less for high speed machining. Automotive and aerospace industries have a large demand for HSK hollow short taper shanks.