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- To: <seaint(--nospam--at)seaint.org>
- Subject: Twist off bolts (was:Bolt retightening)
- From: "Tom Skaggs" <tom.skaggs(--nospam--at)apawood.org>
- Date: Wed, 28 Sep 2005 14:06:16 -0700
From: Michael Hemstad [mailto:mhemstad(--nospam--at)mbjeng.com]
Sent: Wednesday, September 28, 2005 13:36
Subject: Bolt retightening
I concur with Harold (I'm sure he's relieved to hear that). One of the huge and seldom-quoted advantages of twist-off bolts is that they can be inspected with certainty, from the ground, with very little effort on your part. If the spline is twisted off, it's done. Therefore it is entirely feasible to inspect every bolt on a project. It really adds to everybody's peace of mind. And, as Harold notes, it's also probably the cheapest solution.
I've never had to spec these bolts into a project, because they're universally used around here; but if I saw ironworkers using the old-style bolts and spud wrenches, I'd start asking a lot of questions.
Mike Hemstad, P.E.
Meyer Borgman Johnson
From: "Harold Sprague" <spraguehope(--nospam--at)hotmail.com>
Subject: RE: Bolt retightening
Torque wrenches are only supposed to be used in arbitration in the
installation of A325 or A490 bolts according to the RCSC. Torque is a very
poor indicator of tension in a bolt. The tension is what you are trying to
Getting a Skidmore on the project site (hydraulic tension indicating device)
is not a big deal for most iron workers, and is fairly routine.
Because of the variability, I would NEVER allow calibrated wrench bolt
When you boil it all down, the best and probably cheapest solution is to
replace all of the bolts with the tension indicating bolts using the
splines. The installation wrench rotates the nut while holding the bolt.
The spline snaps off when the appropriate tension is achieved. You still
have to install the bolts to "snug tight" with the faying surfaces in full
contact. And you still need the Skidmore on the site to verify the
appropriate tension for the tightening procedure you select. The
installation is a lot easier using the twist offs as opposed to using a
pneumatic wrench or a spud wrench with a cheater (for turn of the nut). The
labor is where you will save the money over other installation methods. And
the QC is better.
If you want the ultimate in reliability, ease of installation, and 100% QC,
use the DTI "Squirter" washers with "twist off" bolts. You get the ease of
installation with the "twist off" wrench and you get the tension indication
that the "squirter" washers provide.
If you decide to go against my incredibly sage advice and use turn of the
nut, use match marking with a paint stick. And never tighten bolts without
>From: Kevin Below <kevinbelow(--nospam--at)videotron.ca>
>Subject: Bolt retightening
>Date: Mon, 26 Sep 2005 22:48:26 -0400
>I am in need of some guidance on the right technique for retightening
>bolts on a 40-year-old steel structure....
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