Analysis of Drilling Process and Processing Issues Related to Drill Bit
The process of drill bit
According to the diameter and total length of the design drill bit, the alloy bar cutting machine can be selected or the wire cutting equipment can be used for fixed-length processing.
The alloy bar which has been cut to a fixed length is processed to straighten the two end faces, which can be achieved on a manual grinding machine.
The chamfering or perforation of the already ground end face of the alloy bar is carried out to prepare for grinding the outer diameter and the handle part of the PDC bit, depending on whether the external circular grinding fixture used is a positive top or a negative top.
The outer diameter of the drill bit, the blank part, and the outer diameter of the handle are processed on a high-precision external cylindrical grinder to ensure the cylindricality, roundness, surface roughness, and other design requirements of the outer diameter.
In order to improve the efficiency of machining on the CNC grinding machine, the drill tip can be chamfered before the alloy bar is fed into the CNC grinding machine, such as 140° drill tip angle, and the chamfer can be roughly ground to 142°.
After cleaning the chamfered alloy bar, it is transferred to the CNC grinding machine process to machine all parts of the PDC bit on a five-axis CNC grinding machine.
If it is necessary to improve the smoothness of the PDC bit chip flute and the outer circle, a wool wheel and abrasive can be used to grind and polish it before or after the fifth step. Of course, in this way, more steps are needed to process the drill bit.
For the qualified PDC bit that has been processed, laser marking is performed on it, and the content may be the company's brand LOGO and the drill bit specification size information.
Package the marked PDC bit and send it to a professional tool coating company for coating.
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If a drill bit chip flute is opened, or if it is helical or straight, this step also includes a negative back bevel around the edge; and then machine the drill tip edge, including the drill tip mesh gap part and the drill tip corner part; then machine the back part of the drill bit's peripheral edge, grind a certain amount of drop to ensure the control of the contact surface between the peripheral edge of the PDC bit and the hole wall of the workpiece at a certain proportion.
For the processing of negative back bevel on the drill tip edge, it can be divided into CNC grinding or manual hand grinding according to different factory processes.
The processing problems of the drill bit
When machining the outer circle of the PDC bit for sale on an external cylindrical grinder, it is necessary to pay attention to whether the fixture is invalid, fully cool the alloy bar during processing, and maintain good habits of measuring the outer diameter of the drill bit tip.
When machining the PDC bit on a CNC grinder, it is advisable to divide the rough and finish processing into two steps in programming to avoid a potentially existing thermal crack caused by too much grinding, thus affecting the service life of the tool.
Use a well-designed material tray to move the tool to avoid the mutual collision between the tools and the damage to the cutting edge.
For the diamond sand wheel that turns black during grinding, use an oilstone to re-profile it in a timely manner.