[TowerTalk] FW: FW: UST bolt Torque question

Tue Jun 25 19:37:04 EDT 2013

Great to have some technical specs for "snug tight".  Thanks.

A hammer struck spud wrench?  I would think the spec means a typical 
tapered spud wrench about 18" long for a 1" bolt.  I'd estimate 
ironworkers I've met can (easily - no insult intended) apply 80 to 100# 
force to a wrench so torques in the 100 to 150 ft-lb range might be a 
numerical range for "snug tight".  IIRC the ironworkers that erected my 
steel building had a 250 ft-lb target for 3/4" A325 bolts, thus I 
assume  they are "slip critical" joints. (They used a big torque wrench).

The spec cites four conditions to satisfy "snug tight"  - 1. the torque 
applied, 2. all plies in firm contact,  3. all bolts equally "snug", and 
4. a  static load.  Towers don't satisfy #4 for anchor or leg bolts 
since leg tension/compression reverses depending on the direction of the 
wind.

Specification for Structural Joints Using High-Strength Bolts, December 
31, 2009  RESEARCH COUNCIL ON STRUCTURAL CONNECTIONS 16.2-29 Section 
4.1     "Snug-tightened joints are also permitted for statically loaded 
applications involving ASTM A325 bolts and ASTM F1852 twist-off-type 
tension-control bolt assemblies in direct tension. However, 
snug-tightened installation is not permitted for these fasteners in 
applications involving non static loading."

hmmm.. perhaps UST compensates by having 4x 1" bolts in each leg for my 
HDX589.  It seems quite unlikely to me that these bolts ever fail in 
shear, which is what holds a snug tight connection together. However, 
long term cycling might cause other failure modes.

I did inspect both of my towers for condition #2, "all plies in 
contact"  Tower 1 passed visual inspection for all bolts having plies in 
firm contact.  Tower 2 has the opening leg flanges in contact and for 
the pivot leg flanges, only 2 of 4 bolts achieve "plies in firm 
contact"  The gap is about 0.030 to 0.050 between plies (flanges) for 
the other 2 bolts.   That is with all bolts torqued to 140 ft-lbs and 
three full cycles of tightening on each flange.  I noticed when 
installing the towers, that the fabrication tolerances are such that it 
took a lot of bolt torque to achieve any contact on some flanges.  I 
opted for enough torque to achieve reasonable contact as my working 
definition of snug tight.

YMMV,

Grant KZ1W

On 6/25/2013 1:12 PM, KM5VI wrote:
> Very well put Mickey and I agree with your 90% comment as well.
>
> Page 51 of the Research Council on Structural Connections (RCSC)
> Specification for Structural Joints Using High-Strength Bolts gives us a
> technical definition for snug tight:
>
> http://www.boltcouncil.org/files/2009RCSCSpecification.pdf
>
> KM5VI
>
>
>
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
> Mickey Baker
> Sent: Tuesday, June 25, 2013 2:38 PM
> To: KM5VI
> Cc:towertalk at contesting.com
> Subject: Re: [TowerTalk] FW: UST bolt Torque question
>
> There are actually technical definitions for this. As you might imagine,
> engineering structures like towers, buildings and bridges, engineers need to
> effectively communicate to laborers how they'd like things tightened.
> Here's an interesting technical treatise from a fastener manufacturer's
> point of view that defines "snug tight" as:
>
> *Snug Tight = The tightness that is required to bring the plies into firm
> contact (Typically obtained with a few impacts of an impact wrench or the
> full effort of an Iron-worker using an ordinary spud wrench).
> *
>
> The original doc can be found at:
> http://www.selfdrillers.com/brochures/TDS012-Turn-of-Nut%20Installations.pdf
>
> Dollars to donuts that the average iron worker will normally tighten a nut
> tighter than 90% of hams. Ironworkers put the world together - and sometimes
> take it apart!
>
> 73,
>
> Mickey N4MB
>
>
> On Tue, Jun 25, 2013 at 3:27 PM, KM5VI<km5vi at flukey.cc>  wrote:
>
>> Snug tight is a standard term commonly used in the design of bolted
>> connections that are not slip-critical.  Slip-critical connections
>> rely on the friction created by the clamping action of the threaded
>> connection and require a minimum fastener torque or bolt stretch
>> specification to achieve the design friction value.  Bolted connection
>> design based on the simple shear and/or bearing strength of the
>> fastener do not rely on joint friction, and thus the assembly torque
>> is non-critical provided that it is tight enough to eliminate slop in
>> the joint that might over time from load cycles (bolt loosening).
>>
>> FYI - I have found a spud wrench useful for snug tight connections on
>> my crank-up tower base connections - it is a short wrench that is
>> designed to be struck with a hammer.
>>
>> Hope this helps.
>>
>> Matt
>> KM5VI
>>
>>
>>
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
>> Jim Thomson
>> Sent: Tuesday, June 25, 2013 7:39 AM
>> To:towertalk at contesting.com
>> Subject: [TowerTalk] UST bolt Torque question
>>
>>
>> I asked UST  how much Torque should be used on both the 12 x  1.125
>> inch anchor rods....and also the 18 x  1 inch leg bolts.
>> I also told em I used never seize on both anchor rods and legs bolts.
>> Also told em the anchor rods are 104 ksi yield strength..and came from
>> portland bolt...and are 60 inchs long each.... with 6 inch threads
>> on each end.   Told em that the 18 x leg bolts are
>> A325 bolts and are 3 inchs long each.    Everything has heavy duty flat
>> washers and slightly oversized nuts on em.
>>
>> Their reply was...... snug fit !    This is for my UST  HDX-689 tower.
>>   This
>> is the old style 689..that weighs 5000 lbs..without the ants and mast,
>> but that
>> weight includes the bearings  and small  PP  rotor.   The crane operator
>> weighed the tower when it was unloaded.
>>
>> What is  ..snug fit ?     Trying to get  answers from UST at times can be
>> exasperating.
>> Does anybody even know ?    I was thinking  perhaps  125 ft lbs for the
>> anchor rods......and 100 ft lbs for the leg bolts.   Leg bolts can always
>> be
>> replaced...
>> anchor rods cant.
>>
>> Tnx...  Jim   VE7RF
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>
> --
> Mickey Baker, N4MB
> Fort Lauderdale, FL
> *"Tell me, and I will listen. Show me, and I will understand. Involve me,
> and I will learn." *Teton Lakota, American Indian Saying.
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>