Drilling Technology Preparation Points
Before work, first, wipe the sliding parts of the drilling machine clean, inject lubricating oil, and move each operating handle to the correct position; then drive slowly, and after a few minutes of trial operation, wait until the mechanical transmission and lubrication system are normal before starting work. If the drilling machine is found to be faulty, it should be checked and adjusted together with relevant personnel. At the same time, a correct workpiece installation plan must be adopted. The space between the drilling machine table or pad and the installation reference surface of the workpiece must be kept clean to ensure smooth contact. The distribution of the compression nails must be symmetrical and the clamping force must be uniform and firm. It is strictly prohibited to Hit the workpiece with a metal object to prevent it from deforming.
During the clamping process, the workpiece should be carefully calibrated to ensure that the center line of the drill hole is perpendicular to the work surface of the drilling machine. When the position accuracy of the drilled hole is relatively high, a reference line should be drawn on the edge of each hole to check whether the drilled hole is deflected. When setting the tool, observe the alignment of the drill bit and die edge from different directions.
Before drilling, make a shallow pit and make sure it is correct before drilling. Before the drill bit is clamped, its handle and the taper hole of the drilling machine spindle should be wiped clean. After the drill bit is installed, the drill machine spindle can be slowly rotated to check whether the drill bit is straight. If there is any swing, the clamping can be changed in different directions to reduce the vibration. Adjust to minimum value. The clamping length of straight shank drill bits is generally not less than 15mm. In addition, do not place objects randomly or hit them on sliding surfaces such as the drilling machine table and guide rails to avoid affecting the accuracy of the drilling machine.
Before drilling, the cross center line of the hole position should be drawn according to the location and size requirements of the hole. The line is required to be clear and accurate. The thinner the line, the higher the accuracy. An inspection circle or inspection box should be drawn as the drilling inspection line. It is convenient to check and correct the drilling position when drilling, and then carefully punch the center punch hole.
The center punch hole should be made a small point first, and then carefully observe the vertical and horizontal directions of the cross center line to see whether the center punch hole is symmetrical on the cross line. At the intersection point, the center punch hole is finally squared and rounded to ensure accurate centering of the drill. This is an important step in ensuring the accuracy of the drilling position.
Factors to Consider When Drilling
Processing Accuracy
When choosing a carbide drill bit, you first need to consider the dimensional accuracy requirements for drilling. Generally speaking, the smaller the diameter of the hole being processed, the smaller the tolerance. Therefore, drill bit manufacturers usually classify drill bits according to the nominal diameter size of the hole being machined. Among the above four types of carbide drill bits, the solid carbide drill bit has the highest processing accuracy (the tolerance range of the 10mm solid carbide 5-gold drill bit is 0mm~0.03mm), so it is the best for processing high-precision holes. choose.
The tolerance range of the welded carbide drill bit 9 U or the replaceable carbide crown drill bit is 0mm~0.07mm, which is more suitable for hole processing with general precision requirements. Drills equipped with carbide indexable inserts are more suitable for heavy-duty rough machining. Although its processing cost is usually lower than other drills, its processing accuracy is also relatively low, with a tolerance range of 0mm~0.3mm (depending on the drill bit). aspect ratio), so it is generally used for hole processing with low precision requirements, or for finishing holes by replacing boring inserts.
Processing Stability
In addition to considering drilling accuracy requirements, the stability of the processing machine tool must also be considered when selecting drill bits. Machine tool stability is crucial to the safe service life and drilling accuracy of drill bits, so the working status of the machine tool spindle, fixtures and accessories needs to be carefully inspected. In addition, the stability of the drill bit itself should also be considered. For example, solid carbide drill bits have the highest rigidity and therefore can achieve high machining accuracy. The structural stability of carbide indexable insert drill bits is poor and prone to deflection. This kind of drill is equipped with two indexable inserts. The inner insert is used to process the center part of the hole, and the outer insert is used to process the outer edge part from the inner insert to the outer diameter.
Since only the inner insert enters cutting at the initial stage of processing, the drill bit is in an unstable state and can easily cause the drill body to deflect. The longer the drill bit, the greater the deflection. Therefore, when using a carbide indexable insert drill with a length exceeding 4D for drilling, the feed rate should be appropriately reduced at the beginning of the drilling phase, and the feed rate should be increased to the normal level after entering the stable cutting phase.
Welded carbide drill bits and replaceable carbide crown drill bits are composed of two symmetrical cutting edges that form a self-centering geometric edge. This highly stable cutting edge design makes it unnecessary when cutting into the workpiece. Reduce the feed rate, except when the drill bit is installed at an angle and cuts into the workpiece surface at a certain angle. At this time, it is recommended to reduce the feed rate by 30% to 50% when drilling in and out. Because the steel of this type of drill bit The drill body can produce slight deformation, so it is very suitable for lathe processing; while solid carbide drill bits are more brittle and are easier to break when used for lathe processing, especially when the drill bit is not in good centering condition.
Chip Removal and Coolant
Chip removal is an issue that cannot be ignored in drilling. In fact, the most common problem encountered in drilling is poor chip removal (especially when processing mild steel workpieces), and no matter what kind of drill bit is used, this problem cannot be avoided. Machining workshops often use the method of externally injecting coolant to assist chip removal, but this method is only effective when the depth of the hole being 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 match the diameter of the drill bit. For machine tools without an internal spindle cooling system, coolant pipes should be used. The larger the hole being processed, the more difficult it is to remove chips, and the greater the coolant pressure required. Therefore, the minimum coolant flow rate recommended by the drill bit manufacturer should be ensured. If the coolant flow rate is insufficient, the processing feed rate needs to be reduced.
Processing Cost Per Hole
Productivity or cost per hole is the most important factor affecting drilling. In order to improve productivity, drill manufacturers are working on research methods that can integrate multiple operating procedures and develop drilling tools that can achieve high feed and high speed processing. The newly developed replaceable carbide crown drill bit has excellent processing economy. After the drill bit is worn, the user does not need to replace the entire drill body, but only needs to replace the carbide crown. The purchase cost is only equivalent to the cost of regrinding a welded or solid carbide drill bit.
Carbide tooth crowns are easy to replace and have extremely high repeatability. The processing shop can use one drill body with multiple tooth crowns to process holes of different aperture sizes. This modular drilling system can reduce the cataloging cost of drill bits with a diameter of 12mm~20mm, and can also save the cost of backup tools required when regrinding welded or solid carbide drill bits. When considering the cost per hole machined, the total life of the drill bit should also be factored into the calculation. Generally speaking, a solid carbide drill bit can be reground 7 to 10 times.
During the drilling process, the details of drilling machine preparation and workpiece clamping are crucial. By selecting the appropriate drill type, ensuring the stability of the machine tool and drill bit, scientific chip removal and cooling, and optimizing the cost of each hole processing, etc., we can effectively Improve processing accuracy and efficiency. In actual operations, process parameters should be flexibly adjusted according to different processing needs, and attention should be paid to equipment maintenance and troubleshooting to ensure the stability and consistency of drilling quality.
