Technical Tutorial - Low cost automation

Dangers in Irrational Use of "Double Nuts"

"Double nut method" is a reliable way to prevent screws from selfloosening. There are, however, some important application key points that need to be well understood. Fig. 1 and Fig. 2 show the representative methods and rules of "double nut" applications. If these rules are ignored, proper "double nut" effect will not be obtained, though the arrangement may seem to be reliable.

Basics of double nut methods for prevention ofscrew loosening

1. Effective when the screws become loose due to vibration inducedscrew rotation.
2. Not effective for loosening due to elongation of bolt's body causedby the material the bolts. Non-rotation type of loosening.
3. Exact procedures must be followed when tightening double nut arrangements. (See Fig. 1)
4. The top nut determines the strength of a double nut arrangement (in principle), so the thickness of two nuts matters greatly. (See Fig. 2)