In the process of tapping workpieces in the machining industry, sometimes due to unreasonable technology (the end face of the threaded hole is processed after welding the workpiece with processed threaded holes), the processing personnel make mistakes in reading the drawings (wrong size) or operating errors (Calculation errors, drilling shallow bottom holes, programming errors, and drilling and tapping threaded hole depth positioning errors) and many other factors lead to the phenomenon that the threaded holes on some workpieces are not deep enough after processing.
Once such problems occur, due to the poor stability of the drilling machine, operators and technicians often directly install the workpiece with the threaded hole to be repaired on the boring machine or milling machine workbench. After correction and fastening, use the threaded hole bottom hole drill According to the correction of the inner diameter of the threaded hole, drill the bottom hole to the depth of the pattern, and then repair it with a tap. However, this method is easy to cause the operator to "frictionally cut" the original thread during the process of deepening the bottom hole, resulting in damage to the existing thread and affecting the processing quality of the threaded hole.
At the same time, this repair method requires the operator to have a good technical level, and it takes a long time to correct the threaded hole, and the work efficiency is very low. The cost of repairing it with boring and milling equipment is also relatively high. In addition, if the end face of the threaded hole is not perpendicular to the centerline of the threaded hole due to reprocessing after assembly welding or other reasons, it will inevitably damage the existing thread during the second drilling of the threaded bottom hole, and also It will inevitably lead to the hidden danger of scrapping or downgrading the threaded hole of the workpiece. After many discussions and experiments, the author has found a series of tricks with faster work efficiency and reliable and stable quality.
1. Method for Repairing Shallow Threaded Hole on Radial Drilling Machine
If the hardness of the workpiece material is high, it can be drilled and tapped on a radial drilling machine when repairing its threaded holes. However, it is necessary to correct the centerline of the threaded hole parallel to the centerline of the spindle of the drilling machine as shown in the figure below, and then directly use the drill bit to correct the threaded hole and the centerline of the drill shaft of the drilling machine to be coaxial, and use the drill bit and tap to meet the required size. Drill and tap shallow threaded holes.
Steps for repairing the threaded hole: first, place the workpiece on the adjustable screw that has been arranged on the drilling machine table; secondly, screw the correction screw into the threaded hole to be repaired and tighten it to ensure that the center line of the correction screw is consistent with the The center line of the threaded hole is consistent; then, put the spindle of the drilling machine close to the calibration screw (a gap must be left to prevent the spindle of the drilling machine from squeezing the calibration screw and affecting the calibration accuracy), and adjust the adjustable screw to make the calibration screw parallel to the spindle of the drilling machine , gradually adjust and close to ensure that the parallelism error is not greater than 0.03mm, a piece of paper can be used to pull the upper and lower parts between the main shaft of the drilling machine and the calibration screw to make it evenly stressed; finally, insert the drill chuck Install it in the spindle of the drilling machine, clamp the modified drill bit in the drill chuck, insert the drill bit into the threaded hole to be repaired, observe that the gap between the shank and the threaded hole is uniform, and drill according to the required size to complete the drill. After the hole is replaced with a tap screw.
The manufacture of the modified drill is very simple, just grind the drill edge length of an old drill until it is sufficient. The straight shank part is evenly ground or turned off by 1mm, so that there is a 1mm gap between the drilled hole and the original threaded hole, and no damage to the existing threads of the threaded hole will occur. The accuracy requirements of the calibration screw are high, and the threaded part must be coaxial with the straight handle part without bending, and its length is generally 3 to 5 times the depth of the thread to be repaired to ensure the calibration accuracy.
2. Method of Repairing Shallow Threaded Hole with Pistol Drill
For workpieces with large volume, heavy weight and soft material (such as aluminum alloy workpieces), when it is necessary to repair the problem of shallow depth of threaded holes with small diameters, you can use the pistol drill to hold the aforementioned modified drill bit and directly drill them , and then manually tap the thread.
3. In conclusion
The method of repairing small threaded holes is very innovative, especially the use of old drill bits and modified drill bits after grinding. The problem. In the actual production process, the repair problem of shallow screw holes can be effectively solved. The method is simple, practical, and can be popularized, so it is worth popularizing.
Chuangtuo Jinggong (Jiangsu) Co., LTD is profession manufacturer of various types of Hexagon Nuts, everything is customized in our factory, Should you have any questions please feel free to come back to us.
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