The depth of threaded inserts is not enough after processing, how to repair it?

In the process of Threading on the working pieces in the machining industry, Sometimes because of the technological process is not reasonable, processing personnel map reading error or other error (the calculation error, drilling shallow bottom hole, programming errors, and drilling and tapping screw thread hole depth positioning errors), and many other factors cause some artifacts on the threaded hole depth is existing after the completion of processing.

Such problems once occurred, due to the poor stability of drilling machine, the operator and technological process personnel often directly to take the unrepair threading inserts mounted on the boring and milling machine worktable, after correction and fastening, the bottom hole bit of the threaded hole is used to drill the bottom hole to the depth of the pattern after correction according to the inner diameter of the threaded hole, and then it is repaired by tapping the thread with a tap. But this method is easy to make the operator in the process of deepening the bottom hole drilling, the original thread "friction cutting", resulting in the destruction of the existing thread, affecting the quality of threaded hole processing.

At the same time, this repair method requires the operator to have a good technical level, and the process of threading hole correction time is long, the work efficiency is very low. The cost of repairing it with boring and milling equipment is relatively high. In addition, if the end face of the threaded hole is not perpendicular to the center line of the threaded hole because of reprocessing or other reasons after being welded, it will inevitably appear in the process of drilling the bottom hole of the thread twice, leading to the destruction of the existing thread, which will inevitably lead to the scrap or degradation of the workpiece threaded hole. After many studies and tests, we found a series of quick ergonomic efficiency, reliable and stable quality tips.

1. The method of repairing thread shallow hole in radial drilling machine

If the workpiece material hardness is high, the repair of the threaded hole can be drilled on the radial drilling machine. However, the center line of the threaded hole should be corrected to be parallel to the center line of the drill press spindle in the way shown in Figure 1, and then directly use a drill bit to correct the coaxial center line of the threaded hole and the drill shaft of the drill press, and drill and tap the shallow threaded hole according to the required size.

1-workbench 2-Adjustable screw 3-workpiece 4-drill press spindle 5-correction lead rod

The steps to repair the threaded hole are as follows: First, we place the work piece on the adjustable screw that has been arranged on the drill press workbench; Secondly, the correction lead screw is screwed into the threaded hole to be repaired and tightened to ensure that the center line of the correction lead screw is consistent with the center line of the threaded hole; Then drilling spindle and correction screw press close to, must leave a gap to prevent drilling spindle will effect correction precision calibration screw extrusion slanting), and adjust the adjustable screw, make adjustment screw at parallel to the axis of the drilling machine, gradually adjust gradually rely on, to ensure that the parallelism error is not more than 0.03 mm, can use a piece of paper in drilling screw spindle and correction between upper and lower part of the draw, Make its force uniform; Finally, the drill chuck is installed in the drill press spindle, and the modified drill bit is clamped in the drill chuck, so that the drill bit is inserted into the thread hole to be repaired. After observing that the gap between the shank and the thread hole is uniform, drill according to the required size, and replace the tap tapping screw after drilling.

The production of the modified drill bit is very simple. The length of the drill edge of an old drill bit is worn as long as possible. The straight shank part is evenly grinded off or turned off 1mm, so that there is 1mm gap between it and the original threaded hole in the drilling, and no damage to the existing thread of the threaded hole will occur.

The precision requirement of the correction lead rod is high. The thread part must be coaxial with the straight shank part, without bending, and its length is generally 3 ~ 5 times of the depth of the thread to be repaired, so as to ensure the correction accuracy.

2. A method of repairing shallow threaded holes with a handgun drill

For large, heavy and soft workpieces (such as aluminum alloy workpieces) that need to fix the problem of shallow thread hole depth with small diameter, the modified drill bit can be held by a handgun drill and drilled directly, and then manually tapped

3. conclusion

The method of repairing small threaded holes is very innovative, especially the use of the old drill car, the modified drill bit after grinding, is a small invention, not only reuse waste materials, but also to solve the more difficult and real problems in the industry. In the actual production process, it can effectively solve the problem of shallow thread hole repair, and the method is simple, practical, and universal, worthy of promotion.