insert bolt

基本解释

A hexagonal molded rubber head forms around the rounded head of the metal bolt insert.
螺栓头部采用六边形形状，内部附有金属。
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First, assembly with temporary bolts. Amount of temporary bolts should be no less than the 1/3 of total connecting bolts. Align steel bar with hole, and insert temporary bolt and screw down nut.
首先用临时螺栓拼装，个数不应少于接头螺栓总数的1/3以上，方法是先用钢穿杆对准孔位，在适当位置插入临时螺栓拧紧螺母；
Slam latch is screwed onto latch support which is either screwed or welded to the door. Assembled without insert it can be opened with a tapered square key. Bolt has free stroke.
这种锁舌用螺丝装在锁支架上，而锁支架用螺丝固定或焊接在门上，无锁芯的装配时，可用锥形四方匙开启锁栓为自由行程。

But invariably there is play between the threads of the bolt and the female insert because the teeth don't fit perfectly.
FORBES: Magazine Article