Before CNC drilling, the corresponding drill should be selected for sharpening. The sharpened drill bit ensures that the top angle, clearance angle and chisel bevel angle are accurate, the length of the two main cutting edges are flat and symmetrical with the center line of the drill bit, and the two main flank surfaces are smooth, in order to facilitate centering and reduce the roughness of the hole wall, and the chisel edge and main cutting edge should be properly ground (preferably rough grinding on a grinder first, and then finishing on a whetstone).
To draw a line accurately with a height gauge, the first thing to do is to ensure that the standard is accurate. When marking, make a 40-60 degree angle between the marking stitch and the marking plane of the workpiece (along the marking direction), so that the drawn lines are clear and uniform. Pay attention to the selection of the scribed datum surface, the datum surface should be processed accurately, and the flatness of itself and the perpendicularity to the adjacent surface should be guaranteed. After the cross line of the hole position is drawn, in order to ensure easy alignment when drilling, use the center punch to punch out the center point on the cross line (requires that the punch point should be small and the orientation should be accurate).
Under normal circumstances, for holes with a diameter of less than 6mm, if the precision is not high, the workpiece can be clamped with hand pliers for drilling; for holes of 6-10mm, if the workpiece is regular and flat, it can be clamped with flat-nose pliers, but the surface of the workpiece should be perpendicular to the spindle of the drilling machine. When drilling a hole with a larger diameter, the pliers must be fixed with a bolt pressing plate; for a large workpiece and the hole diameter is more than 10mm, the method of clamping the pressing plate is used for drilling.
After the workpiece is clamped, don't rush to drop the drill, you should first perform alignment. Alignment includes static alignment and dynamic alignment. The so-called static alignment refers to alignment before the initiation of CNC drilling, so that the center line of the drilling machine spindle and the intersection of the workpiece cross line are aligned. This method is safe and convenient for beginners, and it is easier to grasp, but because for example, the spindle of the drilling machine is not considered. Uncertain factors such as rocking, the drilling accuracy is low. Dynamic alignment is performed after the drilling machine is started. While alignment, some uncertain factors are taken into account, and the accuracy is relatively high.
The detection can accurately and timely find the accuracy of the hole, so that necessary measures can be taken to compensate. During the CNC drilling operation, the processing technology of drilling, reaming and reaming is generally used for holes with high drilling accuracy. After drilling the small hole in the first step, use a caliper to detect the wrong offset from the center of the bottom hole to the reference plane, and convert the position between the bottom hole and the ideal center after the actual measurement. Properly increase the top angle of the drill bit, weaken the automatic centering effect, push the workpiece in the positive direction, and gradually increase the diameter of the drill tip to compensate. If the error is greater than 0.10mm, the side walls of the bottom hole can be trimmed with assorted round files, and the trimmed part should be connected to the arc of the bottom hole with a smooth transition.