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RE: Def.: Snug-Fit

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The RCSC does not apply to anything other than high strength bolts. The size bolts you listed are not A325 or A490.

The only problem with "over torquing" is thread deformation or stripping. And that is only a problem if you re-use a bolt. If it is damaged in the installation to the point where the bolt can not be tightened, the bolt is simply replaced. This can happen in A325 / A 490 bolts as well.

If it is a big concern, use a stronger bolt (something in a grade 5 or so). If you have good quality control for lubrication, burrs, etc. get a Skidmore and determine the appropriate torque to match the tension that you need. It sounds like bringing the faying surfaces into contact is not a problem. The issue then becomes what is the bolt tension requirements and what is the purpose of the bolt tension.

Use the NASA 1228 book by Barrett.

Harold Sprague

From: "Michel Blangy" <mblangy(--nospam--at)>
Reply-To: <seaint(--nospam--at)>
To: <seaint(--nospam--at)>
Subject: RE: Def.: Snug-Fit
Date: Tue, 13 Mar 2007 14:41:49 -0800

"firm contact" is the focus of debate in the office here. I have also seen
"positive contact." The worry around here is that the bolts may be over
torqued/stripped. How to prevent this is the problem. Bolt dias. I am
concerned about are on the order of 1/4 to 3/8. Parts for assembly are
generally well aligned bearing surfaces parallel.

Michel Blangy, P.E.
  -----Original Message-----
  From: Doug Mayer [mailto:doug.mayer(--nospam--at)]
  Sent: Tuesday, March 13, 2007 12:58 PM
  To: seaint(--nospam--at)
  Subject: RE: Def.: Snug-Fit

  Installation requirements for snug-tightened joints can be found in the
"RSCS Specification for Structural Joints Using ASTM A325 or A490 Bolts",
which is at the back of the AISC Steel Manual.  The specific section for
installation is 8.1 and it says that "the snug-tightened condition is the
tightness that is attained with a few impacts of an impact wrench or the
full effort of an ironworker using an ordinary spud wrench to bring the
connected plies into firm contact."

  Hope that helps.

  Doug Mayer, SE

  Structural Engineer



  7535 North Palm Ave., Suite 201

  Fresno, CA 93711

  (559) 437-0887 Ph.

  (559) 438-7554 Fax



  From: Tom Skaggs [mailto:tom.skaggs(--nospam--at)]
  Sent: Tuesday, March 13, 2007 1:35 PM
  To: seaint(--nospam--at)
  Subject: RE: Def.: Snug-Fit

  Would you care to provide a reference to this definition?


  From: ECVAl3(--nospam--at) [mailto:ECVAl3(--nospam--at)]
  Sent: Tuesday, March 13, 2007 13:04
  To: seaint(--nospam--at)
  Subject: Re: Def.: Snug-Fit

  Hand tight + 1/3 turn with wrench (not impact wrench)

  Stephen Macie, P.E.



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