A finishing grinding method for large precision threaded holes

Abstract

The invention discloses a method for finishing and grinding a large accurate threaded hole and a grinding tool. The grinding tool mainly comprises a grinding bar body, a threaded face matched with the threaded hole is machined and formed on the outer circle end face of the grinding bar body, grinding paste with proper granularity is selected to coat the threaded face of the grinding bar body and / or the threaded surface inside the threaded hole, the grinding bar body is screwed into the threaded hole for repeated grinding, all microcosmic protruding parts on the inner threaded surface of the threaded hole can be grinded away gradually through the pressure between the threaded face of the grinding bar body and the threaded surface inside the threaded hole and the polishing function of grinding material particles of the grinding paste, and therefore the defects of tiny scratches, cyclone milling chatter marks, large-area serious corrosion and the like on the threaded surface are overcome, it is guaranteed that the size precision of the large threaded hole is met, meanwhile, excellent threaded surface quality is obtained, the effect is uniform, repair risks are low, the operation process is easy to quantize and control, and the method and grinding tool are used for the technical field of large threaded hole machining.

Description

technical field [0001] The invention relates to the technical field of large threaded hole processing, in particular to a grinding method for large precision threaded holes. Background technique [0002] At present, in the field of large-scale or heavy-duty machinery and equipment manufacturing, the processing and handling of large-scale precision threaded holes are relatively common, such as pressure vessels of pressurized water reactor nuclear power plant reactors with harsh service conditions, small dimensional tolerance range and strict control, and high surface quality requirements The processing technology of the M155 screw hole on the body flange is one of the difficulties in the entire product manufacturing process. Such large threaded holes are likely to have large-scale surface defects on the threaded tooth surface, such as large-area heavy corrosion caused by improper protection, and lines left by the vibration of the tool when the thread is whirl milled. [0003...

AI Technical Summary

Problems solved by technology

[0004] If you choose to use machining equipment such as boring and milling machines for repairing, first of all, due to the limitation of work positions, the equipment may not be able to be arranged or may be difficult to arrange

Secondly, the requirements for repeated alignment of machining equipment are very high. It must be ensured that the deviation between the zero point of the tool shaft center at the time of rework and the zero point of the tool shaft center at the time of original machining is small enough, otherwise the thread machine on one side will not be able to be added, or even lost. scrapping

In addition, in order to ensure the cutting quality, the cutting amount should not be too small, so the margin for repairing must be sufficient. If it is a screw hole whose dimensional tolerance is already close to the upper limit, there will undoubtedly be a big overshoot if it is repaired by machining. poor risk

[0005] If you choose a special large-scale tap of the corresponding specification for retapping and repairing, first of all, you must first prepare a large-scale tap of the corresponding specification; It is difficult to manufacture and expensive, and there are many inconveniences and risks in use. For example, if the tap is stuck on a certain tooth in the screw hole when it is re-tapped, it may cause serious damage to the screw teeth.

[0006] If you choose an electric or pneumatic tool and a special dish-shaped grinding wheel to grind tooth by tooth, the necessary condition of this method is that the special dish-shaped grinding wheel must be suitable and reliable, and the operator must be skilled enough. Only by slight contact with the tooth profile can it be realized that when the grinding tool rotates at high speed, it will not cause additional damage, the grinding amount is out of tolerance, and the grinding amount is uneven throughout the circle, which will make the roundness of the screw hole worse; and this method has been used for dimensional tolerances. For screw holes that are close to the upper limit, the processing risk is still greater

[0007] If you choose electric or pneumatic tools plus special wire brushes or nylon brushes for grinding and polishing, the contradiction of this method is that tube brushes (wire brushes or nylon brushes) may not be able to effectively eliminate defects (grinding force) for different types of surface defects. not enough), or the grinding effect is more than necessary and is not easy to control

For example, for the flutter lines or scratches on the thread surface processed by cyclone milling, nylon brushes cannot be used to remove them, and wire brushes are risky, and it is easy to leave a large number of new scratches on the tooth surface; in short, this method is difficult to balance Effect and thread safety

[0008] If you choose sandpaper to grind tooth by tooth manually, this method is relatively safe and safe, but the disadvantage is that the efficiency is very low, and because it is manual operation, it is difficult to guarantee the uniformity of polishing due to factors such as changes in the hand feeling of personnel.

[0009] In short, there is a big risk in the rework process of large threaded holes by the above method, and it is difficult to ensure the surface quality of the threads of large threaded holes

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