Snug Tight Connections - specifiy a torque? 1

[StructureMan44]

When specifying that connections be snug-tight, do you also specify a minimum torque the bolt must be tightening too or does snug-tight imply a specific torque?

 

[RonRoberts]

Snug tight is defined in AISC Section J3, 1 as being the tightness attained by a few impacts of an impact wrench or the full effort of a worker with an ordinary spud wrench that brings the connected plies into firm contact.

 

[Ron]

Specify one or the other...not both.

 

[Leftwow]

I read a little about this. I'm assuming that snug tight would be just enough amount of normal force to create enough friction to prevent the bolt nut from loosening.

 

[ajh1]

There is no defined torque requirement for a snug-tight bolt. Actually there is no defined torque requirement for any structural bolt. Pretensioned bolts have a mandatory tension requirement as determined by a Skidmore test prior to commencement of installation. Actual torques will vary for a given tension depending upon the condition of the bolt at the time of installation (lubrication, dirt, etc.) As noted above by RonRoberts, this is the current definition of a snug tight bolt in RCSC.

 

[Tomfh]

There's no specific torque for snug-tight. It just means the plies are in firm contact and someone has given it a few impacts with an impact gun (similar to doing up wheel nuts with a rattle gun), or given it full effort with an impact wrench (similar to doing up wheel nuts with a tyre iron).

As a side note, in my experience it's really really hard to get steel erectors to give you anything better than snug tight.

 

[CELinOttawa]

By the way, just to give you an idea of how simple and fundamental this is, for a very long time the Canadian code only allowed finishing of a bolt by "snug tight plus one quarter turn". Word was that was going to change, but I haven't had any reason to check... That fact should go a long way to show how reliable the simple snug tight spud wrench treatment can be!

 

[Nutrin14]

Considering 250N hand tightened force applied using standard podger spanner, torque for snug tight connections shall be arrived for different bolt diameters. Please refer Table H.62 of "Joints in Steel Construction: Simple Connections" published by BCSA.

Same issue was raised by a site QC guy in one of our projects to substantiate torque requirement for snug tight bolted connections and we resolved using the above said document as back up.

 

[Leftwow]

I agree with CELinottawa mainly because you can break the low strength bolts if you aren't careful. There is a reason the bolts are only "snug tight" so be careful. If you've ever worked in the field I'm sure you've seen that before.

 

[Tomfh]

250N sounds too wimpy. I can put far more than that onto a spanner, and I don't pull spanners for a living.

 

[Nutrin14]

There was an earlier thread about this issue i noted just now. Please refer below link for further details which may be useful.

http://www.eng-tips.com/viewthread.cfm?qid=213305

Thanks.