Looseness Prevention Countermeasures
| Effect | Function | Adaptation example |
|---|---|---|
| Initial loosening countermeasure |
Spring pressure | Disk spring washers, spring washers |
| Collapse loosening countermeasure |
Reducing the surface pressure | Highly rigid flat washers |
| Return rotation resistance |
Stopping mechanical rotation | Slotted nuts, split pin-attached bolts, tongued washers, claw washers |
| Increasing the screw part’s degree of adhesion |
Sheet metal screws, coiled inserts | |
| Increasing the return torque | Non-metallic insert-attached detent nuts (e.g. nylon, nuts, nylock), all-metallic detent nuts (e.g. U nuts), flange-attached bolts (e.g. flange nuts, skirt nuts), pre-belling torque form nuts (e.g. tough lock nuts, space lock nuts) |
|
| Return rotation prevention |
Forced locking by eliminating the fitting gap |
Double nuts Hard Lock Nuts |
| Solidification and adhesion within the fitting gap |
Anaerobic glue (e.g. Lock Tight), glue-containing capsule-attached bolts (e.g. chemical anchor bolts) |
Countermeasures Evaluation
A. The return rotation resistance-use group are countermeasures that in almost all cases can prevent any reduction in the pretension force (axial force), which means that their effectiveness against looseness due to return rotation is considered high. However, in the case of double nuts, unless they are completely locked (pinioned), their performance is likely to decline remarkably, as has been shown in variety of tests. Also, anaerobic glue does not exhibit its effectiveness unless it is used in line with the using instructions. Compared with these measures, at the present time Hard Lock Nuts are considered to be the most effective connection method available.
