In the process of tapping the workpiece in the machining industry, sometimes the process is unreasonable (the end of the threaded hole is processed after the workpiece has been machined with the threaded hole), the reading error of the processing personnel (wrong size) or the operation error (Calculation errors, drilling shallow holes, programming errors, and drilling and tapping hole depth positioning errors) and many other factors lead to insufficient depth of threaded holes on some workpieces after machining.
Once such problems occur, due to the poor stability of the drilling machine, operators and process technicians often install the workpiece to be repaired on the threaded hole on the boring machine or milling machine table. After the tightening is corrected, the threaded hole bottom hole drill bit is used. According to the inner diameter of the threaded hole, the bottom hole is drilled to the depth of the pattern, and then the tap is tapped and repaired. However, this method is very easy for the operator to "frictionally cut" the original thread during the process of deepening the bottom hole, which causes the existing thread to be damaged, which affects the processing quality of the threaded hole.
At the same time, this repair method requires the operator to have a better technical level, and the thread hole correction process takes a long time and the work efficiency is 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 center line of the threaded hole due to re-machining after welding or other reasons, it will inevitably cause damage to the existing thread during the secondary drilling of the threaded bottom hole. It will inevitably lead to the hidden danger of scrapping or degrading the threaded hole of the workpiece. After many discussions and experiments, the author has found a series of tricks with quicker work efficiency and reliable quality.
1. Method for repairing shallow thread holes on a rocker drilling machine
If the workpiece material has a high hardness, it can be drilled on the rocker drill when repairing the threaded hole. However, first adjust the center line of the threaded hole parallel to the center line of the drill spindle according to the method shown in the figure below, and then directly correct the threaded hole and the center line of the drill shaft with the drill bit, and use the drill bit and tap according to the required size. Drilling a shallow hole with a shallow depth.
To repair the threaded hole: first, place the workpiece on the adjustable screw that has been placed on the drill table; secondly, screw the calibration screw into the threaded hole to be repaired and tighten to ensure the correct centerline of the screw The center line of the threaded hole is consistent; then, the drill spindle is close to the calibration screw (the gap must be left to prevent the drill spindle from squeezing the calibration screw and affecting the correction accuracy), and the adjustable screw is adjusted to make the calibration screw parallel to the drill spindle Gradually adjust to make sure that the parallelism error is not more than 0.03mm. You can use a piece of paper to pull the upper and lower parts between the drill spindle and the calibration screw to make the force even. Finally, the drill chuck will be drilled. Installed in the drill spindle, the modified drill is clamped in the drill chuck, the drill is inserted into the threaded hole to be repaired, and the gap between the shank and the threaded hole is observed to be uniform, and then drilled according to the required size to complete the drilling. After the hole, replace the tap tapping screw.
The modification of the drill bit is very simple, and the length of the drill bit of an old drill bit can be ground enough. The straight shank portion is evenly ground or removed by 1 mm so that there is a gap of 1 mm in the drilled hole with the original threaded hole, and no damage to the existing thread of the threaded hole occurs. The accuracy of the precision screw is high. The threaded part must be coaxial with the straight shank. There must be no bending, and the length is generally 3 to 5 times the depth of the thread to be repaired to ensure the accuracy of the correction.
Second, the method of repairing the shallow hole with a pistol
For workpieces with large volume, heavy weight and soft material (such as aluminum alloy workpieces), it is necessary to repair the problem of shallow depth of the threaded hole with small diameter. The drill can be directly drilled by the pistol drill. Then use manual tapping.
Third, the conclusion
The method for repairing small threaded holes is very innovative. In particular, the use of old drill bits and modified drill bits after grinding is a small invention. It not only reuses waste materials, but also solves the more difficult and practical existence of the industry. The problem. In the actual production process, it can effectively solve the problem of repairing the shallow thread hole. The method is simple, practical, and can be popularized, and it is worth promoting.
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