NJATC Torque

  1. How is the grade of a bolt determined? WB9

    An SAE bolt thread size is determined by measuring what? WB9
    By adding the number 2 to the number of hash marks on the bolt head

    threads per inch
  2. An ISO bolt thread size is determined by measuring what? WB10
    mm form crest to crest
  3. the length of a bolt is determined by measuring what? WB10
    The length of the shaft
  4. The formula for torque is what? WB1
    Torque = length x force
  5. The fastening process is comprised of four distinct phases. WB7
    • Run Down
    • Alignment
    • Elastic
    • Plastic (yield)
  6. The total force required in a torque application is comprised of two distinct regions. What are they? WB6

    Defined how?
    • Static breakaway torque
    • Dynamic applied torque

    • Static breakaway torque: the friction the fastener must overcome
    • Dynamic applied torque: the torque required to move or rotate the fastener after it has been seated
  7. What is the 90/10 rule regarding friction? PP7
    90% of torque is friction and 10% is stretch
  8. The direction of the torque can be determined by using the right hand grip rule: ……which is?
    if the fingers of the right hand are curled from the direction of the lever arm to the direction of the force, then the thumb points in the direction of the torque.[6]
  9. Some estimate that adding a lubricant could reduce the required torque reading by up to? What %
    40 percent
  10. even though you can’t see it, a tightened bolt has been stretched a microscopic amount, and this stretch is called Tension.

    Just like a stretched spring, which tends to pull back into its original shape, a stretched bolt tries to pull itself back to its normal state. It’s this pulling back force, called the “_______” that actually maintains the tightness of the joint.
    clamp force

    Note: But lubrication on the bolt threads—and a whole host of other factors—can cause fluctuation in torque readings. So once you add a lubricant of any kind to the threads, all bets are off as to whether the same torque setting will truly secure the bolt. That’s because nobody really knows how the lubricant affects the torque measurement on a bolt without performing a scientific study using expensive lab instruments.
  11. Describe the benefits of a smart bolt.
    Image Upload 1
    A smart bolt allows you to not worry about the tension being used for torque and especially when lubrication and stainless steel are involved.
  12. Is a stainless torque value different than a non-stainless torque value?
    yes.  Usually 2-3 lbs difference.
  13. Can you use a lubricant with a stainless fastener and should you for torque value?
    No.  Because this can change the torque reading by as much as 40%
Card Set
NJATC Torque