In summary, a lockwasher of this type is useless for locking.” At this time it is equivalent to a solid flat washer, and its locking ability is nonexistent. However, the washer is normally flat by the time the bolt is fully torqued. The section on lockwashers states: “The typical helical spring washer … serves as a spring while the bolt is being tightened. NASA on the topic in 1990 (reference publication 1228). There have also been comments about the validity of the anti-vibration washers (both polymer and 'anti-lock') so I guess do your research if this is a concern for you! There are many many great links and comments in this thread.ĭespite their ubiquity and reputation, split washers do nothing to prevent bolts loosening off and in some tests actually quite significantly aid in loosening.

Eg a metal bolt on the wooden leg of a table, and its purpose is to spread the pressure of the bolt across a broader area, so you can tighten more without the bolt just sinking into the soft woodĮdit: you do also see rubber or plastic washers for metal on metal fastenings, this is usual to prevent vibration from loosening the bolt over time.Įdit 2: wow - thanks everyone! Many people have pointed out other reasons why washers are used in addition to the above including to prevent certain types of corrosion, to carry the wear for fastenings which are frequently used (like on access panels) and to seal against moisture. In general, a washer is used when the material you're fastening is softer than the material you're fastening with.

Order of lock washer and flat washer