Original title: Operation steps of drilling and summary of methods to improve drilling accuracy! I. Basic concept of drilling Drilling refers to the machining process in which a hole is made in a solid material with a drill bit. In general, when drilling a material on a drill press, the drill bit should perform two movements simultaneously: ① Main motion, that is, the rotary motion of the drill bit around the axis (cutting motion); ② Auxiliary motion, that is, the linear motion (feed motion) of the drill against the workpiece along the axial direction. When drilling, due to the defects of the drill structure, the machining quality of the workpiece will be affected to a certain extent. The machining accuracy is generally below IT10, and the surface roughness is about Ra12.5 μm, which belongs to rough machining. II. Operation steps of drilling 1. Marking: Before drilling, be familiar with the requirements of the drawing first. According to the requirements of the position and size of the drilling hole, use a height ruler to mark the cross center line of the hole position. The center line should be clear and accurate, and the thinner the better. After marking, use a vernier caliper or a steel ruler for inspection. 2. Draw inspection grid or inspection circle: after the line is drawn and the inspection is qualified, the inspection grid or inspection circle with the hole center line as the symmetrical center shall be drawn as the inspection line for trial drilling, so as to check and correct the drilling position during drilling. 3. Proofing and punching: After drawing the corresponding inspection grid or inspection circle, the proofing and punching shall be done carefully. Punch a small point first, and observe carefully in different directions of the cross center line to see whether the sample punch hole is on the intersection of the cross center line. Finally, punch the sample punch hole with force, round and enlarge it, so as to accurately set the drill center. 4. Clamping: Clean the machine tool table, fixture surface and workpiece reference surface, and clamp the workpiece. The clamping shall be smooth and firm for easy observation and measurement. Attention shall be paid to the clamping method of the workpiece to prevent deformation of the workpiece due to clamping. 5. Test drilling: test drilling must be carried out before drilling: make the chisel edge of the drill bit align with the center of the hole to drill a shallow pit, and then visually check whether the position of the shallow pit is correct, and constantly correct the deviation to make the shallow pit coaxial with the inspection circle. If the deviation is small, the workpiece can be pushed to the opposite direction of the deviation while pulling out, so as to achieve gradual correction. 6. Drilling: The fitter's drilling is mainly done by manual feeding. When the test drilling meets the accuracy requirements of the drilling position, the drilling can be carried out. During manual feeding, the feeding force shall not bend the drill bit to avoid skewing of the hole axis. III. Methods for improving drilling accuracy 1. Grinding the drill bit is the premise. Expand the full text The corresponding drill bit shall be selected for sharpening before drilling. In addition to the accurate top angle, relief angle and chisel edge bevel angle, the two main cutting edges are equal in length and symmetrical with the drill center line, and the two main flank surfaces are smooth, in order to facilitate centering and reduce the roughness of the hole wall, the chisel edge and the main cutting edge should also be properly ground (it is best to grind roughly on the grinder first, Borehole Drill Bits , and then refine on the oilstone). 2. Accurate marking is the foundation Precise scribing with a height ruler shall be carried out to ensure accurate dimensions. When scribing, an included angle of 40 ~ 60 degrees shall be formed between the scriber angle and the scribing plane of the workpiece (along the scribing direction), so that the scribed lines are clear and uniform. Attention shall be paid to the selection of the reference plane for scribing. The reference plane shall be processed accurately to ensure its own flatness and perpendicularity to the adjacent plane. After the hole reticle is drawn, in order to ensure easy alignment during drilling, the center punch shall be used to punch out the center point on the reticle (it is required that the punching point shall be small and the position shall be accurate). 3. Correct clamping is the key In general, for holes with a diameter less than 6mm, if the accuracy is not high, the workpiece can be clamped with pliers for drilling; for holes with a diameter of 6 ~ 10 mm, if the workpiece is regular and flat, it can be clamped with flat 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 flat pliers must be fixed with the bolt pressing plate; when drilling a hole with a larger diameter of more than 10 mm, the method of clamping the pressing plate shall be used for drilling. 4. Accurate finding is the key point After the workpiece is clamped, do not drop the drill in a hurry, and align it first. Alignment includes static alignment and dynamic alignment. The so-called static alignment refers to the alignment before the drilling machine is started, so that the center line of the drilling machine spindle is aligned with the intersection point of the workpiece cross line. This method is safe and convenient for beginners, and it is easy to master. However, because it does not consider uncertain factors such as the swing of the drilling machine spindle, the drilling accuracy is low. The dynamic alignment is carried out after the drilling machine is started, and at the same time, some uncertain factors are taken into account, so the accuracy is relatively high. 5. Careful testing is indispensable. The inspection can accurately and timely find the accuracy of the hole, so that necessary measures can be taken to remedy it. For holes with high drilling precision, we generally adopt the processing technology of drilling, reaming and reaming. After the small hole is drilled in the first step, the caliper is used to detect the error offset from the center of the bottom hole to the datum plane, and the position between the bottom hole and the ideal center is converted through actual measurement. If the error is not more than 0.10 mm, the remedy can be made by properly increasing the vertex angle of the drill bit, weakening the automatic centering effect, properly pushing the workpiece in the positive direction, and gradually increasing the diameter of the drill point. If the error is greater than 0.10 mm, the two side walls of the bottom hole can be trimmed with an assorted round file, and the trimmed part shall be smoothly connected with the arc of the bottom hole. 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