The nut, the screw and the washer (and, possibly, the screw security) together constitute the screw binding. The threaded drill of the nut fits onto a screw of the same size, and its external form is designed in a way that sufficient torque for the pulling can be exercised upon it with an appropriate tool. The most common form is the hexagonal design, suitable for use with spanner, ring spanner or wrench. If there is a risk of vibration, you need to make sure that the nut cannot loosen: this can be done with a specially designed nut or with extra screw security. The size and material of nuts are regulated by international standards, most nuts are mass-produced, but there are unique specimens produced by machining, serving special purposes.

Categorization by material and material quality
  • iron
  • toughened steel
  • anti-corrosion steel (A2)
  • acid-resistant steel (A4)
  • yellow copper
  • aluminium
  • chemically resistant plastic (PA)
The most common types according to quality
  • 5.0 quality type
  • 8.0 quality type
  • 10.0 quality type
  • DIN 934 –Hexagonal nut
  • DIN 1587 –Closed tall nut
  • DIN 917 –Closed short nut
  • DIN 315 –Screw bolt
  • DIN 439 B – Short nut
  • DIN 6334 – Binding nut
  • DIN 980 V –Self-securing nut
  • DIN 985 –Self-locking nut with plastic lining
  • DIN 6923 – flange nut (knurled and smooth)

The DIN 6923 hexagonal flange nuts are most commonly used in machine industry, such as car manufacturing or lift structures. The flange ensures greater pulling torque and the knurls further increase the tightness of the binding.