Bolt Threads in a Shear Plane 1

[struclearner]

Dear All,
In a Bolted Joint, the threads are not good in the shear plane of the joint.
In the tapped bolted joint, what is the best practice to start threads on bolt/member, are the threads start a little lower than the surface of the lower member of the joint which has internal threads.
Thanks for your input.

 

[BridgeSmith]

I wouldn't say the having threads in the shear plane is "not good". Threads in the shear plane reduces the design shear capacity, but most of the bolted connections for the bridges we design have, or are assumed to have, threads in the shear plane. We just design for the lower shear capacity and move on, rather than sweating where the threads end.

 

[ajh1]

In a tapped bolted joint I believe you will always have threads in the shear plane. If you stop the threads below the shear plane (assuming the bolt head is at the top), then the shank of the bolt is in the shear plane (which is good), however you can't thread a shank into a hole that is threaded for the same nominal size thread. The discussion of bolts in shear plane vs. bolts not in shear plane is only really valid when the bolt uses an external fastener, i.e., a nut, to tighten with and all members through which the bolt goes have shank-sized (or larger) non-threaded holes.

 

[LionelHutz]

GM has used recessed thread holes for the motor starters for years. The bolt has part of the shank knurled to get it to fit tighter in the starter hole and the non-threaded part of the hole in the block. That allows the bolts to locate the starter and keep it straight on the block. So, it is possible to do it that way. Easier would be to just design to the lower shear of the threaded part of the bolt.