carbide drill bit selection

The so-called carbide is tungsten carbide powder as matrix, cobalt powder as a binder by pressurized sintering. Generally contain 94% tungsten carbide, 6% cobalt. Because of its high hardness, very wearable, a certain strength, suitable for high-speed cutting. But the  fibre discs  toughness is poor, very brittle, in order to improve the performance of cemented carbide, and some use carbide substrate in a chemical vapor deposition on a 5-7 micron layer of special hard titanium carbide (TIC) or titanium nitride (TIN), to has a higher hardness. Some use ion implantation technology, titanium, nitrogen, and carbon injection the matrix certain depth, not only improves the hardness and strength and regrinding the drill can move into when they injected ingredients. There is a physical method to generate the bit at the top of a layer of diamond film, which greatly improves the hardness and wear resistance of the drill.
Drill material selection
The processing characteristics of the material required bit has the following characteristics: hardness of the drill must be greater than the hardness of the workpiece; drill workpiece as to withstand a considerable torsional and axial forces, it must have sufficient strength and toughness; Since the processed material toughness, requiring cutting edge sharp enough, so the tool material must have sufficient wear resistance, so as to reduce the work hardening; Since the chemical properties of the workpiece to be higher, thus requiring the tool material and titanium affinity worse in order to avoid the spread of stroke caused by sticking knife, broken drill phenomenon.
Currently, the tool for doing extremely numerous types of materials, including tool steel, carbide, superhard materials.
Initially, attempts to carry out the ordinary high-speed steel drills coated test, inexpensive ordinary high-speed steel drills, when using coating technology, can significantly reduce the friction coefficient of the tool and the workpiece, to improve tool life. However, due to the higher speed machine, using drill strong enough, causing the  wet polishing pad drill breaks during processing, the effect is not ideal.
Carbide is the latest developed a tool material, suitable for most materials, rough finish, such as steel, cast iron, special materials and plastics. To this end, decided to use solid carbide drill bit.
Drill grinding to determine the parameters
1 Twist the main auxiliary plane
Twist several major auxiliary plane base surface, cutting plane, the profile and column profiles.
If you do not consider supplementary motor, the main cutting edge twist drill of any point on the base surface, the architectural features of the twist drill, drill points on the main cutting edge of the base surface is variable.
Any point on the main cutting edge of the cutting plane, a cutting direction but contains the point tangent to the plane of the surface of the machining point. Perpendicular to the cutting plane and the base plane, and the main cutting edge of the cutting plane of the points are not the same. Any point on the main cutting edge of the column cross-section through the center line of the drill point and the center line of the cylindrical surface and do, the main cutting edge on a different type of column cross-sectional radius of the cylindrical face.
2 Twist drill main geometric parameters of the selection
Twist drill main geometric parameters include the choice of angle drill, drill cutting edge rake angle and clearance angle choice drill bit life helix angle on edge of impact analysis and related processing.
Drill angle determines the width and drill chips the size of the anterior horn. When the drill diameter and feed rate constant, increasing the angle, the iron narrowing unit to reduce the load on the cutting edge. Angle has a great influence on the rake angle, a corresponding increase in angle will help to improve terrible at cutting conditions. Influence the direction of chip flow angle. According to the relevant tool design data, combined with the hardness of the processed products is not high, but the viscous characteristics, select the drill angle of 140 °.
The first twist angle is other geometric parameters of the bit decision. In high-speed cutting machine tools, rake angle on the cutting deformation and cutting force has little effect, while using a smaller rake angle can be enhanced tip strength. This angle is determined, after the angle, the more sharp edge, but it will be reduced accordingly wedge angle impact tool strength and heat dissipation area. To this end, the selected bit smaller horn, taken as 8 °.
3 drill bit life helix angle on impact analysis
Shows the shape characteristics of the  9 inch saw blade twist drill points on the cutting edge is variable helix angle, the helix angle of a direct impact on the rake angle of the main cutting edge. Helix angle is larger, the more sharp edge, cutting more light, otherwise it will cause severe hardening makes the blades wear out quickly. According to the relevant tool design data, take the helix angle of 30 ° to meet the application requirements, while allowing for mass production.
4 edge correlation processing
The processing includes chisel edge correction, chamfering and inverted blade and other measures. For the material to be processed, machining properties, processing parameters and conditions such as clamps, cutting edge of the bit for a suitable passivation, improve drilling performance of the drill bit, reduce tool wear.
Coating technology
In the case of constant cutting parameters, in order to improve production efficiency and reduce production costs, use of the tool coating technology to reduce tool wear, in order to improve tool life is increasingly becoming a trend.
Tool coating refers to the strength and toughness of cemented carbide or high speed steel (HSS) surface of the substrate by vapor deposition method, a thin layer of good wear resistance of the coating of refractory metal or non-metal compounds. As a chemical barrier coating and thermal barrier, reducing the tool and the workpiece between the diffusion and chemical reaction, thereby reducing tool wear. Coated tool with high surface hardness, good wear resistance, chemical stability, heat resistance, oxidation, friction factor is small and low thermal conductivity and other characteristics.
After coating the drill after a number of processing has been improved significantly, unit cost is greatly reduced.
Carbide hardness and strength, not only the ratio of cobalt and tungsten carbide, but also with the powder particles about. Carbide drill ultra fine particles, and its average grain size of tungsten carbide with 1 micron or less. This bit is not only high hardness and compressive strength and flexural strength are improved. To save costs Many drill shank welded structure, the original as a whole are carbide drill, drill shank back now made of stainless, but significantly reduced the cost of the material due to different concentricity less than its dynamic rigid whole alloy drill, particularly in the small diameter side.