Answers

  1. Yes. There are many different types of markings depending upon the standard to which it was made. For example; an ‘A4’ indicates it to be type 316 stainless steel with Metric threads.
  2. If it is a brass nut it means it has left-hand threads, such as for an acetylene tank regulator. On a steel tubing nut, it differentiates between an SAE 45º seat and a 37º JIC fitting. For a standard hex nut, it would identify Grade 5 compatibility.
    1. The male threads were cut, not roll formed.
    2. The nut grade is not compatible with the grade and hardness of the bolt.
    3. Accidental presence of a lubricant.
    4. Non judicious use of a power wrench.
  3. Actually, it will be less. The modulus of elasticity between the bolts is quite different. Simply put, it takes more energy to stretch the harder bolt the same distance. It will be impossible to achieve the same clamp load using the same torque value.
  4. There are at least 6 solutions; some include increasing the bolt grade and having closer tolerance holes.
  5. If it was properly torqued, no. If this fact was not true, connecting rod bolts and pistons would be flying from every engine because they are in a ‘wet’ environment.
  6. Under normal conditions (98%), none. There is only one condition that will allow reuse. This means that if the nut is only backed off a little, without even bringing the connection to zero load, and the nut is retightened from that point, the connection does not have the planned clamping load and is in jeopardy of failing.
  7. Approximately 10-15%.
  8. Yes. Using a wrought washer; using a USS washer for anything other than sheet metal or wood, using a USS washer one size down that will interfere with the fillet radius of the bolt; using the ‘sharp’ side of a single punched hardened washer against the bolt head, which could induce stress raisers in the fillet.
  9. Applying Hooke’s Law, there are 4,256 pounds of clamp load lost, or about 1/3.