What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
When the mechanical components are installed on the concrete foundation, the J-shaped and L-shaped ends of the bolts are embedded in the concrete for use. The tensile capacity of the anchor bolt is the tensile capacity of the round steel itself. The size is equal to the cross-sectional area multiplied by the allowable stress value (Q235B: 140MPa, 16Mn or Q345: 170MPA), which is the allowable tensile capacity at the time of design. The anchor bolts are generally made of Q235 steel, which is smooth and round. Rebar (Q345) is strong, and the thread of the nut is not as easy to be round. For light round anchor bolts, the burial depth is generally 25 times its diameter, and then a 90-degree hook with a length of about 120mm is made. If the bolt diameter is large (such as 45mm) and the buried depth is too deep, a square plate can be welded at the end of the bolt, that is, a large head can be made (but there are certain requirements). The burial depth and hook are all to ensure the friction between the bolt and the foundation, so as not to cause the bolt to be pulled out and damaged.
Nut fasteners are used in various industries with connection and fastening requirements, such as vehicles, construction machinery, agricultural machinery, manufacturing machinery, etc. For large construction machinery or construction vehicles, due to the harsh working environment and the action of heavy loads, the nut fasteners on it are subjected to vibration and load impact in all directions, which makes the nut easier to loosen, resulting in tightening. The function of the device is reduced or even failed. cause a great safety hazard.
structure for concealing installation screws, comprising a locking piece, a driving piece, a bottom plate, a blocking cover and a handle head, the lower ends of the two locking pieces are provided with positioning holes, and the locking pieces pass through the positioning holes and the locking piece positioning posts on the base Snap and fix, the middle of the two locking pieces is provided with a protruding point, the movable groove of the driving piece corresponds to the protruding point of the nine locking pieces for fixing, the riveting point holes and screw holes of the bottom plate and the riveting points of the base The position that matches the screw holes and is fixed by screws, the blocking cover is directly inserted into the bottom plate, and the blocking cover is fixed by the rotating drive piece, the handle head is inserted into the base, and the slot of the handle head moves to the locking piece at the locking piece Lock the handle.
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.
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