What factors need to be considered when choosing carbide drill bits?

1. Processing accuracy


When choosing a carbide drill bit, you first need to consider the dimensional accuracy requirements for drill bit processing. Generally speaking, the smaller the hole diameter, the smaller the tolerance. Therefore, drill bit manufacturers often classify drill bits according to the nominal diameter size of the hole being machined. Among the above four types of carbide drill bits, solid carbide drill bits have high processing accuracy (the tolerance range of 10mm solid carbide drill bits is 0~0.03mm), so they are suitable for processing high-precision holes; welded carbide drill bits Or the tolerance range of replaceable carbide crown drill bits is 0~0.07mm, which is suitable for hole processing with general precision requirements; drill bits equipped with carbide indexable inserts are suitable for heavy-duty rough machining. Generally, the processing cost is lower than other drill bits, but the processing accuracy is also low, with a tolerance range of 0~0.3mm (depending on the aspect ratio of the drill bit), so it is generally used for hole processing that does not require precision, and for replacing boring tools for finishing holes. of finishing.


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2. Processing stability


In addition to the requirements for drill bit accuracy, the stability of the machine tool also needs to be considered when selecting a drill bit. The stability of the machine tool is crucial to the safe life and accuracy of the drill bit, so it is necessary to carefully check the working status of the machine tool spindle, fixtures and accessories. In addition, the stability of the drill bit itself also needs to be considered. For example, carbide drill bits have high overall rigidity, so they can achieve higher machining accuracy.


3. Chip removal and coolant


Chip removal is a problem that cannot be ignored in drilling processing. In fact, a common problem in drilling is poor chip discharge, especially when machining mild steel workpieces. Furthermore, there is no way to avoid this problem with any drill bit. At the machining site, coolant is often injected to assist in chip removal. This method is only effective when the depth of the hole to be processed is smaller than the hole diameter and the cutting parameters are reduced. In addition, the appropriate coolant type, flow rate, and pressure must be selected to suit the diameter of the drill bit. If the machine tool is not equipped with an internal cooling system in the spindle, please use a coolant pipe. The deeper the hole machined, the more difficult it is to remove chips and the greater the coolant pressure required, so it is necessary to ensure the minimum coolant flow rate recommended by the drill manufacturer. When the coolant flow rate is insufficient, the processing feed rate needs to be reduced.


4. Processing cost per hole


Productivity and cost per hole are important factors affecting drilling. In order to improve productivity, drill manufacturers are working on machining methods that can integrate various operating processes and developing drill tools that can achieve high-feed, high-rotation machining. The developed replaceable carbide crown drill bit has a good processing economy. After the drill bit is worn, the user does not need to replace the entire drill bit but only needs to replace the carbide crown. The purchase cost is equivalent to the cost of regrinding a welded or solid carbide drill bit. Carbide crowns are easy to replace and have high repeatability. Multiple crowns can be installed with just one drill at the processing site and holes of different diameters can be processed. This modular drill bit system can not only reduce the cataloguing cost of drill bits with a diameter of 12~20mm but also save the cost of supporting tools required to regrind welded or solid carbide drill bits.

When considering the processing cost of each hole, the total life of the drill bit must also be calculated. Generally speaking, a solid carbide drill can only be reground 7 to 10 times, a welded carbide drill can only be reground 3 to 4 times, and a replaceable carbide crown drill can be used when processing steel. , the steel drill body can replace the dental crown at least 20 to 30 times.

Since welded or solid carbide drill bits need to be reground, in order to avoid tool breakage, factories tend to use lower cutting parameters when using this drill bit, which also affects the productivity of the drill bit. In addition, the replaceable carbide crown drill bit does not need to be ground again. There is no need to worry about crown damage at the manufacturing site, and large feeds and cutting speeds can be used.

In most cases, the cutting edge shape and edge treatment state of welded or solid carbide drill bits after regrinding are difficult to be completely consistent with new drill bits, so their cutting performance is also somewhat different from new drill bits. In addition, if the cutting edge is not properly treated during the regrinding process, the edge may be easily damaged, the drill torque and drill force will increase, the cutting heat will increase, and the drill life will be shortened. New carbide crown drill bits provide a more consistent service life.

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