液压千斤顶又称机械式千斤顶，是由人力通过螺旋副传动，螺杆或螺母套筒作为顶举件。
The hoisting jack calls the mechanical hoisting jack, is by the manpower through the screw vice-transmission, the screw rod or the nut sleeve achievement goes against lifts.
直接拧入式螺杆的极限抗拔力随着拆装次数的增多而下降，但是，当拆装次数为8-9时，极限抗拔力仍然可达到尼龙预埋螺母的水平。
It declines with the increase of times of direct assembling bolt knocked-down. But it can still reach that of nylon inbuilt nut after knocked-down 8 to 9 times.
直接拧入式螺杆的极限抗拔力随着拆装次数的增多而下降，但是，当拆装次数为8-9时，极限抗拔力仍然可达到尼龙预埋螺母的水平。
It declines with the increase of times of direct assembling bolt knocked-down. But it can still reach that of nylon inbuilt nut after knocked-down 8 to 9 times.
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