Slip Critical w/o Bearing? 6

[KootK]

The usual process with SC bolts is to design such that the service loads don't slip and the factored loads can be resisted in common bearing if necessary.

If the bearing mechanism is simply unavailable to you for some reason, do you have the option of designing your connection as slip critical for the factored loads? My gut tells me no but I figured I'd ask around before I abandon the idea...

 

[ToadJones]

Yep...galvanized paint; still not the cleanest way to go.

Galvanized nuts are over-tapped prior to being galavanized.
The Bolt threads are standard threads.
The build-up from galvanizing is accounted for in the over-tapped nut.

 

[paddingtongreen]

A better explanation than I could provide, from:

http://www.appliancedesign.com/CDA/Archives/bf1bc1ef5ba38010VgnVCM100000f932a8c0____

"When zinc parts rub against other parts — particularly other zinc parts — galling (adhesive wear) occurs. The more rubbing that takes place and the greater the load, the worse galling becomes, and the surfaces tend to cling to each other. In the early symptoms, galling causes moving parts to hesitate, plungers to stick, levers to bind. Occasionally, they chatter as they stick, release and stick together again. This is the slip-stick tribological phenomenon. Eventually, part-to-part welding occurs and the mechanism fails."

As galvanized bolts are torqued, pressure between the thread surfaces increases. Most steel erectors know to make sure the lubrication is there, but the torque/tension ratio needs to be established in a Skidmore if you are trying for a predetermined tension.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[BAretired]

Another possibility is to use Huck Ultra-Twist Blind Bolts. I have never used them myself, but they seem like a good alternative to this problem. But the holes would need to be drilled, not flame cut.

BA