carbide drill considerations

Selection of carbide drill, you first need to consider the size of drilling accuracy requirements. Generally, the smaller the aperture is processed, a tolerance is smaller. Therefore, manufacturers usually drill the hole to be processed according to the nominal diameter of the drill bit segments. In the above four types of carbide drills in solid carbide drill highest precision (φ10mm solid carbide drill tolerance range is 0 ~ 0.03mm), so it is the best choice for machining precision holes; welded carbide replaceable carbide drill or drill crown tolerance range is 0 ~ 0.07mm, more suitable for general accuracy of hole machining; installation carbide indexable insert drill is more suitable for heavy roughing, Although its processing cost is generally lower than several other bits, but its precision is relatively low, the carbide grinding wheels  tolerance range is 0 ~ 0.3mm (depending on the aspect ratio bits), so it is generally used for hole machining accuracy is not required , or by dress finished hole boring finishing blades.
(2) processing stability 
In addition to considering drilling accuracy requirements, the need to consider when you select the drill machine tool stability. Machine stability and service life for the safety drill drilling accuracy is essential, therefore need to carefully examine the machine spindle, fixtures and accessories working condition. Also, consider the stability of the drill itself. For example, the overall rigidity of the best carbide drill, so you can achieve very high precision. The carbide indexable insert drills structural stability is poor, prone to deflection. This bit is installed on two indexable inserts, inserts for machining holes in which the inner central portion of the processing of the outer blade at the outer diameter from the inner to the outer periphery of the blade portion. Since the initial stage in the processing of only the inner blade into cutting, drilling in an unstable state, can easily cause the drill body deflection, and the drill bit longer, the greater the amount of skew. Therefore, the use of longer than 4D carbide indexable insert drills for drilling, the drilling phase at the beginning should be appropriate to reduce the feed rate, cutting into the stable phase after the feed rate to normal levels . Welded carbide replaceable carbide drill bit and drill crown is composed of two symmetrical cutting edge geometry may be self-centering blade type, which has a high stability of the cutting edge designed to cut into the workpiece without reduce feed rate, and only when the bandsaw blades  bit inclined installation into a certain angle with the surface of the workpiece when cutting exception, this time recommended drill, drill feed rate will decrease from 30% to 50%. Because these drill steel drill body can produce small deformation, making it ideal for lathe; rather brittle solid carbide drills due for lathe machining easier to break, especially when the centering drill bit in poor condition This is especially true.
3 Chip and Coolant
BTA is drilling problems can not be ignored. In fact, most drilling encountered problem is poor chip removal (machining mild steel workpiece is especially true), and regardless of drills were unable to avoid this problem. Processing plant are often used outside the way into the auxiliary coolant chip, but this method only in the machining hole diameter and reduce the cutting depth is less than the case where parameters are valid. In addition, you must use the drill diameter to match the proper coolant type, flow and pressure. For the cooling system is not installed on the machine tool spindle, you should use coolant ducts. The deeper the hole to be machined, chip more difficult and requires the greater the pressure of the cooling fluid, should be recommended by the manufacturer of drill minimum coolant flow, such as cooling liquid flow rate is insufficient, the need to reduce the machining feed rate.
4 processing cost per hole
Productivity or each hole drilling processing costs affecting the most important factor. In order to improve productivity, drill manufacturers are working on a variety of operating processes can be integrated processing methods and the development to achieve high feed, high speed processing of the drilling tool.
The newly developed replaceable carbide drill crown has excellent machining economy. Bit wear, the user does not have to replace the entire drill body, you can simply replace the carbide tooth crown, and its purchase price is equivalent to welded or solid carbide drill regrinding a fee. Carbide crown replacement is easy and repeatable high precision, machine shop can drill body with a plurality of teeth crowns, to the processing of different pore size holes. This modular drilling system can be reduced 12 ~ 20mm diameter drill cataloging costs, but can also save on welding or grinding of solid carbide drills need to re-backup tool costs.
In considering the processing cost per hole, the total lifetime of the drill should be counted. Generally speaking, a solid carbide drill regrinding only 7 to 10 times, a welded carbide drill regrinding only 3 to 4 times, and replaceable carbide drill crown in the processing of steel material When the steel of the drill body can be replaced at least 20 to 30 times the crown.
As welded or solid carbide drills need to re-grinding, in order to avoid tool breakage, workshops in the  wet tile saw use of such drills tend to use lower cutting parameters, thus also affect drilling productivity. The replaceable carbide drill crown without regrinding, the workshop can be used in the processing of the largest feed rate and cutting speed without having to worry about damage to the crown.
In many cases, the solid carbide drill or welding after regrinding of the cutting edge shapes and edge processing state is difficult to completely match with the new drill bit, so the cutting is some difference with the new drill. In addition, if re-grinding process of the cutting edge mishandled may easily damaged blade, drilling torque and increased drilling force, cutting heat increase, leading to drill shortened life expectancy. While the new replaceable carbide drill life of the crown is more consistent.