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RE: Bolt Tightening

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Jimmy C.....

Take a look at the "Specification for Structural Joints Using ASTM A325 or
A490 Bolts" by RCSC (I'm looking at the November 13, 1985 one that was
issued with the 9th edition ASD).  If you look 8., (d), (1), you'll see it
states:

"A representative sample of not less than three bolts and nuts of each
diameter, length and grade to be used in the work shall be checked at the
start of work in a device capable of indicating bolt tension.  The test
shall demonstrate that the method of estimating the snug-tight condition and
controlling turns from snug tight to be used by the bolting crews develops a
tension not less than five percent greater than the tension required by
Table 4."

A torque indicating wrench (in my honest opinion) does not constitute a
device capable of indicating bolt tension (it indicates torque which is in
turn calibrated by some method to equate to a given amount of tension in the
bolt).  There are 4 methods for achieving pretension on bolts (turn-of-nut,
calibrated wrench, alternate design bolts, and direct tension indicator).
What you described to me seems like a blend of the first two....... in fact,
if the inspector was using a calibrated toque wrench the RCSC spec requires
that the toque wrench be calibrated on a daily basis (again with a device
capable of indicating actual bolt tension).

I believe I'm looking at this correctly, but hey, I've been wrong
before....... maybe Charlie Carter can clarify for us.......

Robert C. Rogers, PE 
robert.rogers(--nospam--at)woolpert.com <mailto:robert.rogers(--nospam--at)woolpert.com>  

Woolpert LLP 


-----Original Message-----
From: c2 [  <mailto:jimmycccccc(--nospam--at)email.msn.com>
mailto:jimmycccccc(--nospam--at)email.msn.com]
Sent: Friday, January 19, 2001 8:35 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Bolt Tightening



    <<  Also, the turn of the nut method requires "calibration" using a
device such as a Skidmore-Wilhelm Bolt Tension Calibrator.  >>

I believe you to be wrong in this premise.  The turn of the nut from snug
tight to 1/3-1/2 more turn is used in lieu of a Skidmore-Wilhelm type
device.  I have used the turn of the nut method on many steel erection jobs
and never had an inspector turn it down.  Usually 10 percent of bolt groups
are checked with a torque indicating wrench by the inspecting authority.  A
tensioned bolt is a tensioned bolt regardless of the means used to achieve
that end.

I have found the calibrated air wrenches to be extremely sensitive to the
consistency of the air supply employed.  Distance from the compressor or air
receiver, efficiency of the compressor and even temperature can effect the
desired result.

Short of a wring-off type of bolt I have found that the tension indicating
washers afford the greatest amount of confidence to an ironworker along with
comparative ease with which they can be inspected and verified.

When I retire I intend to offer pre-flattened tension indicating washers to
the construction industry.  <G>


Jimmy  C.......(hisself)




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