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Difference between a snug tight and a fully tensioned bolt?

  1. Aug 12, 2013 #1
    anyone knows the difference between a snug tight and a fully tensioned bolt?
    thanks in advance:thumbs:
     
  2. jcsd
  3. Aug 12, 2013 #2

    Simon Bridge

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    Turn the bolt until it stops, there is little or no visible gap and does not rattle when you shake it - a low-to-nil setting on a torque wrench for eg or just "finger tight". This is "snug tight".

    The bolt will turn further than that - when it is turned to a non-zero setting on the torque wrench, it is a tensioned bolt. When it is tensioned to the enginerring spec, then it is "fully tensioned". Above or below the spec then it is over or under tensioned respectively.

    http://www.skf.com/files/880426.pdf
     
  4. Aug 12, 2013 #3
    thanks very much, simon.
    it helps.
     
  5. Aug 13, 2013 #4
    The more you pretension a bolt, assuming you are doing it correcting (e.x. using washers), the better that bolt can resist fatigue due to cyclic or repeated loading. So, there are sometimes fundamental reasons for pretensioning bolts to a certain spec, aside from making sure the bolt doesn't come loose..
     
  6. Aug 13, 2013 #5

    Simon Bridge

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    ... which is the most likely way someone may be puzzled about this :)
    ... and the link in post #2, reappearing in #3, goes into detail - yep.

    And people think that "doing up bolts" is simple ;)
     
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