Get to Know the Different Types of Lock Washers and Their Uses

Lock washers are specially designed tools that are used to make sure that bolted joints don’t come loose. There are generally two types of lock washers based on their locking action. These are spring action lock washers and tooth lock washers.

Spring action lock washers can be recognized by their helical shape. These washers are commonly placed under screw heads or nuts. They compress as the fastener tightens. The lock washer’s spring back tension prevents the bolted joint from loosening and at the same time compensate for certain degrees of material wear. Spring type lock washers flatten when they are tightened, which means a slight loosening or "give" has to be allowed for the locking action to come into play.

Tooth lock washers on the other hand, come in internal, external, countersunk external, and internal-external types. Instead of a springing action, tooth lock washers create a ratchet action as it bites into the screw head or the nut and the surface in contact. One downside of tooth lock washers is that it tends to scratch mating surfaces. Despite this, however, they are still very widely used in various types of applications.

A unique type of lock washer, lock-set pair washers or vibration-resistant washers are also seeing widespread use especially in high-vibration environments. Also called Nord-Lock washer assemblies, lock-set pairs consist of two parts—a top piece and a bottom washer. Vibration resistant washers are reusable. They have wedges that interlock on one side and radial teeth on the other. As the nut or screw is tightened, the washer’s teeth bite into the screw head or the nut as well as the mating material, thus preventing slippage. The wedged side increase surface tension, which helps resist loosening.

Other types of lock washers also exist varying only in design and locking mechanisms. Among these are:

• Hi-Collar lock washers – These lock washers have small outside diameter, making them a good fit for space-limited areas and smaller head screws. They are much thicker than typical lock washers, which work to preserve locking ability.
• Countersunk external tooth lock washers – These washers are used with 82-degree oval and flat head screws in countersunk holes.
• External tooth lock washers – These washers are designed for large screw heads. They have wider-reaching teeth, which results in higher twisting resistance.
• Internal tooth lock washers –These washers work best with smaller screw heads and in situations when the washer teeth must be hidden from view.

Fasteners Plus International is a full line fastener distributor, who provides a wide range of standard, metric and custom fastening solutions to users around Chicago, US.