What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
This clearance determines how much the bone fragment fixed by means of the locking screw in the corresponding locking hole can move relative to the nail and thus also relative to other bone fragments fixed by the same nail due to the rigidity of the nail. Together with the flexibility of the material and the overall device this can build up to a size that prevents or decisively delays effective healing. In order to ensure the applicability of the locking device to the surgeon, this gap, although unavoidable, is clinically undesirable in some indications (eg in the case of metaphyseal fragments). Even a screw with a full cross-section, which can have an internal thread in the locking hole, is not gapless. This internal thread only prevents possible axial movement of the screw on the locking screw.
Most of the electroplating used for rivet nuts on the market is environmental protection blue zinc, because the salt spray test time of environmental protection blue zinc can reach 72 hours, that is, three days. This kind of electroplating has a longer salt spray resistance time. In fact, for example, for electroplating white nickel, the salt spray time of white nickel is relatively short, and it usually rusts in a few hours, which is less than 10 hours. However, some can be oiled for electroplating white nickel, and the salt spray time of the rivet nut after oiling can be longer. S series rivet nuts are made of free-cutting iron, which is treated after heat treatment. CLS series rivet nuts are made of easy-to-cut stainless steel. The hardness of low-carbon steel plates without surface treatment must be less than 70RB, and the hardness of stainless steel plates must be less than 80RB.
The technical problem to be solved by Yueluo is to provide a medical self-locking screw, which can fix the inner screw inside the outer screw, expand the outer screw head through the thimble on the inner screw, and use the outer cone on the inner screw. The body expands, compresses the surrounding bone, and achieves a double locking effect through the self-locking between the internal and external screws; it can hook the surrounding fixed parts when the anti-retraction ring is retracted to achieve the anti-regression effect; effectively prevent false implantation. After a long period of service, the looseness, fretting and other adverse reactions of the body are used to solve the defects caused by the existing technology.
The grooved embedded parts are pre-embedded in concrete, and then placed in the groove with T-bolts. After adjusting the fixed position, the fixed object is locked with a nut to achieve the fixing effect. When the grooved embedded parts are embedded vertically in the concrete or at a certain angle to the horizontal line, the T-bolts are likely to move in position before they are tightened. In particular, when fixing heavy equipment, multiple T-bolts are required, and multiple groups of workers are required to help and positioning is difficult, and the installation process is complicated.
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