Flat Washers and Lock Washers: What Are Their Differences?
Washers are a common hardware component that can be found in countless fastened assemblies, often coming in the form of thin, disk-shaped elements that contain a hole. Varying in type, shape, and general design, most washers serve roles including acting as threaded fastener load distributors, spacers, springs, wear pads, preload indicating devices, locking devices, and vibration reducers. In particular, flat washers and lock washers are some of the most common washer options when creating assemblies, and they both offer different capabilities and designs that can make them beneficial for select applications. In this blog, we will briefly discuss both the flat washer and lock washer, allowing you to better understand how they may be used.
Flat Washer
The
flat washer, otherwise known as a plain washer, is considered to be the most basic type of the component family. Most of the time, these hardware components will come in the form of a flat annulus or ring that is constructed from a metal material such as stainless steel, high-carbon steel, brass, or copper. With their simplistic design, flat washer components are primarily used for distributing the load of fasteners such as bolts and nuts. For their installation, the tail-end of the bolt is passed through the hole of the washer until the head is resting on the surface of the component, and then a nut can be secured to the opposite side of the assembly. Beyond serving as a load distributor, flat washer components may also be used when the hold of an assembly is of a greater diameter than the nut that is to be installed.
Lock Washer
The
lock washer is a more complex option, often being designed to be tightened against a fastener for the means of preventing loosening as a result of vibration. To do this, ample torque must be induced during the installation process so that spring tension is applied. Typically, the lock washer will be placed on the nut side of the fastener due to the way in which loosening occurs. Lock washers can be made from various hardened metals, the most common options being stainless steel, galvanized steel, zinc-plated steel, and silicone bronze. Additionally, their most common applicational uses are within transportation industries, mitigating the potential hazards stemming from vibration for automobiles, aircraft, and marine vessels alike.
While different plain washers may be fairly similar to one another, lock washers come in two distinct types, those of which are spring action/split washers and tooth washers. Split lock washers feature a helical shape where a split is made along the circumference, and the component is not completely flat when placed on a surface. As the component is fastened in an assembly, the two opposing ends will exert a spring force that bolsters friction to prevent movement. Useful for smaller loads, split lock washers are the most common type of the part family.
Internal use lock washers are another type, exhibiting teeth that protrude from the surface of the component. This allows for the washer to “bite” into
fasteners and the surface material as contact is established. External use lock washers are a similar type, and their teeth contact the bearing surface. As compared to internal-tooth washers, the external use lock washer can ensure a better hold across a larger radius to support bigger fasteners. When using any type of tooth lock washer, it is crucial that you understand that there is a risk that the washer will scratch and wear down surfaces they lock onto, as this may be a concern to some.
When installing a lock washer, there are some important considerations that should be made prior to making a purchasing decision and before assembling. The first factor that one should consider is where the lock washer is to be used and what type will best serve the need. Then, the fastener that will be installed should have its shank width measured so that an accommodating lock washer can be found. Once all parts are in-hand and ready to go, the lock washer will be placed under the
threaded fastener, and all teeth should be engaged with the surface if present. If everything looks good, the fastener should be tightened with an appropriate tool until a firm connection is established. Before moving on, the lock washer should be tested so that loosening prevention is guaranteed to the best ability. It is always important to not over-tighten a lock washer during the installation process, as too tight of a fit can actually deter performance.
Conclusion
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