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Oct. 22, 2023
Metric tab lock washers are mechanical locking components used to restrict unwanted rotation of nuts, bolts or other compatible threaded fasteners.
Depending on the design, a tab lock washer can incorporate internal tongues, external tabs, locking lugs or multiple formed features that interact with the fastener and surrounding assembly.
Unlike locking methods that depend primarily on friction or prevailing torque, tab washers can create positive mechanical rotational restraint by physically connecting the fastener to a stationary reaction feature.
The fundamental engineering principle is:
Stationary feature → tab washer → threaded fastener
For the locking system to function correctly, the complete mechanical path must be defined.
JUXIN FASTENERS supplies standard and custom metric tab lock washers, locking washers, stamped components and made-to-drawing fastening solutions for OEM and industrial applications.
A metric tab lock washer is a washer-type locking component dimensioned for use with a metric fastening or shaft system.
Depending on the application, it may be installed with:
hex nuts;
round nuts;
shaft locknuts;
bolts;
threaded shafts;
application-specific threaded components.
The washer contains one or more features designed to prevent relative rotation after the threaded fastener reaches its required installed condition.
These features can include:
internal tongues;
external locking tabs;
long tabs;
short tabs;
double lugs;
multiple locking tabs;
keyed locating features.
The exact geometry depends on the locking architecture.
Metric tab washers are sometimes treated as one specific product.
That is misleading.
The term metric primarily identifies the dimensional or mating fastening system.
The actual locking principle depends on the washer geometry.
Two washers intended for the same nominal metric fastener can have completely different:
inside profiles;
outside diameters;
tab positions;
locating features;
locking interfaces;
installation methods.
Therefore, nominal fastener size alone is not enough for accurate sourcing.
The most common principle is positive mechanical restraint.
After the threaded fastener is tightened, a designated washer feature is formed or positioned so that rotation is physically restricted.
For example, a system may use:
shaft keyway → internal washer tongue → washer body → external tab → locknut
Another assembly may use:
housing edge → long tab → washer body → short tab → hex nut
These are different geometries, but the engineering logic is similar:
The washer must be restrained, and the fastener must be restrained relative to the washer.
A major error in the previous version of this article was describing tab washers as though their main locking mechanism were elastic spring force.
That is not the defining mechanism of a tab lock washer.
The primary function of a tab lock washer is typically mechanical rotational restraint.
This distinguishes it from spring-type washers whose behavior is based on elastic deformation and contact conditions.
Metric tab lock washers should also not be confused with sealing washers or gaskets.
A conventional tab washer is not selected primarily to:
seal fluids;
seal gases;
compensate for gasket compression;
prevent leakage.
If a joint requires both locking and sealing, those functions should be evaluated separately unless the specific component has been explicitly engineered and validated to provide both.
There is no single universal tab washer geometry.
The following categories describe common engineering architectures.
Long tab washers incorporate an extended external tab that can be formed against a suitable reaction feature.
Depending on the assembly, the tab may interact with:
a nut flat;
bolt head;
housing;
bracket;
adjacent stationary feature.
The critical question is not simply how long the tab is.
It is:
What does the tab physically lock against?
Long tab washers are covered in more detail in our Long Tab Washers engineering guide.
Double-tab or double-lug washers incorporate two functional locking or locating features.
One feature may restrain the washer while another locks the threaded fastener.
For example:
stationary housing → Tab A → washer → Tab B → nut
Two tabs do not automatically mean greater locking strength.
Their value often comes from performing two different mechanical functions.
See our Double Tab Lock Washers guide for detailed design considerations.
Some shaft-locking systems use an internal tongue or key that engages a shaft keyway.
An external tab can then be bent into a compatible locknut feature.
The resulting locking path becomes:
shaft → keyway → internal tongue → washer → external tab → locknut
This architecture is common in certain shaft and bearing-related locking arrangements.
The washer must match both the shaft interface and compatible nut geometry.
Some designs incorporate multiple external tabs.
Multiple tabs can provide alternative locking positions around the circumference.
This can be useful when the final angular position of the nut cannot be predicted precisely before tightening.
The selected tab can then be formed according to the approved assembly procedure.
Unused tabs do not necessarily increase locking performance simply by being present.
Some washers use a single locating lug primarily to prevent the washer itself from rotating relative to the surrounding structure.
Another geometry or locking feature then restrains the threaded component.
These designs illustrate why each tab should be evaluated by function, not just appearance.
OEM equipment may require a washer geometry that does not correspond exactly to a standard catalog configuration.
Custom designs can include:
non-standard internal profiles;
asymmetric tabs;
special angular relationships;
multiple tab lengths;
housing-specific locating features;
restricted outside diameters;
special material or coating requirements.
For these components, the assembly drawing is often more useful than the washer drawing alone.
These terms can overlap, but they are not always identical.
A round nut lock washer may be designed specifically for a compatible shaft and round locknut system.
A metric tab washer is a broader category that can include locking designs for different metric nuts, bolts and shafts.
When sourcing a replacement component, identify the actual mating geometry rather than relying solely on the product name.
"Stop washer" is sometimes used commercially for washer designs that restrict rotation or movement.
However, terminology varies between industries and suppliers.
For engineering procurement, a drawing, standard designation or complete mating-component description is more reliable than the term stop washer alone.
A spring washer and tab washer operate differently.
Uses elastic geometry and contact behavior.
Uses a mechanical feature to restrict rotation.
They should not be considered direct equivalents simply because both appear in locking-washer product categories.
Serrated lock washers interact with mating surfaces through serrations and friction-related effects.
Tab washers create a physical rotational barrier.
Selection should be based on the actual joint architecture and validation requirements.
Prevailing-torque nuts incorporate rotational resistance within the nut.
A tab washer creates an external locking relationship between the threaded fastener and another structural feature.
A prevailing-torque nut may be useful when no external reaction geometry exists.
A tab washer may be useful where:
positive mechanical restraint is required;
a suitable reaction feature exists;
visual inspection is useful;
the tab can be accessed after tightening.
Neither solution is universally preferable.
Threadlocking adhesive relies on chemical interaction within the threaded joint.
Tab washers rely on mechanical geometry.
Adhesive selection can depend on:
materials;
surface condition;
temperature;
chemical exposure;
curing requirements.
Tab washer selection depends more heavily on:
physical geometry;
locking path;
tab accessibility;
mating fastener position.
The assembly requirements determine the appropriate method.
A mechanically locked tab can restrict fastener rotation.
That does not make the entire bolted joint immune to failure.
Joint performance still depends on:
preload;
external loading;
joint stiffness;
thread condition;
fastener strength;
mating materials;
installation;
service environment.
Tab locking should therefore be treated as one element of the fastening system.
The fastener generates preload when tightened.
The tab washer then restricts unwanted rotation.
The sequence is:
1. Establish the required fastener condition.
2. Establish the mechanical locking condition.
The washer should not be expected to compensate for incorrect tightening.
The correct selection process begins with the assembly rather than with a catalog diameter.
Consider the following engineering questions.
Identify whether the target component is:
a hex nut;
round nut;
shaft locknut;
bolt head;
another threaded component.
This defines one side of the locking interface.
The washer needs a mechanical reference.
Possible features include:
shaft keyway;
housing edge;
bracket;
slot;
machined flat;
another fixed feature.
Without a reaction feature, a positive locking path may not exist.
This question is frequently overlooked.
If the washer rotates freely with the nut, bending a tab against the nut may not create the intended locking system.
An internal tongue, locating lug or external reaction tab may be needed.
The nut or bolt must first reach its required installed condition.
Its final angular position then affects tab alignment.
A well-designed washer provides a practical locking position without requiring inappropriate changes to fastener preload.
The assembly must provide physical access for the forming operation.
Consider:
surrounding components;
tooling clearance;
assembly sequence;
production-line access;
maintenance access.
A washer that fits geometrically but cannot be formed after installation is not a practical solution.
Tab washers can be effective in serviceable equipment, but removal normally requires the locking tab to be bent away from the fastener.
If repeated disassembly is expected, the replacement policy should be considered during product design.
Metric tab washers require material properties appropriate for both manufacturing and final tab forming.
Material selection should consider:
strength;
ductility;
formability;
thickness;
corrosion resistance;
temperature;
operating environment.
Suitable carbon steels and stainless steels can be used depending on the application.
Carbon steel can provide an economical solution for many industrial assemblies.
Where environmental protection is required, a suitable surface finish can be specified.
Material grade, thickness and processing should be selected according to the actual mechanical requirements.
Stainless steel may be selected for corrosion-resistant environments.
However, stainless grades differ in mechanical and forming behavior.
The material must remain suitable for the required tab-forming operation.
Corrosion resistance alone should not determine the selection.
The old article listed metal, stainless steel, rubber and plastic as equivalent material options.
That mixes fundamentally different component families.
A conventional positive-locking tab washer depends on formed mechanical features capable of transferring rotational reaction.
Rubber and polymer washers can perform other functions such as:
isolation;
cushioning;
insulation;
sealing;
surface protection.
They should not automatically be categorized as equivalent metric tab lock washers.
For steel tab washers, finish selection can depend on:
corrosion exposure;
mating materials;
temperature;
customer specification;
coating thickness;
post-coating forming.
If tabs are bent after coating, coating behavior at the bend should be considered.
Many metric tab washers are suitable for sheet-metal stamping.
Depending on geometry, manufacturing may include:
blanking;
piercing;
tab cutting;
forming;
deburring;
heat treatment where applicable;
surface treatment;
inspection.
The exact process depends on the washer design.
Standard designs can be economical when the mating assembly follows an established configuration.
Custom washers may be preferable when:
the housing geometry is unique;
a standard tab cannot reach the reaction feature;
space is restricted;
non-standard shaft dimensions are used;
special tab orientation is required;
the OEM requires a proprietary locking arrangement.
The commercial decision should consider both piece price and the cost of modifying the surrounding assembly.
Depending on the washer architecture, function-critical dimensions may include:
inside diameter;
internal tongue dimensions;
outside diameter;
material thickness;
tab length;
tab width;
tab angular position;
slot geometry;
bend location.
Not every dimension requires the same tolerance.
Functional tolerancing can improve manufacturing economics while preserving assembly performance.
The locking tab undergoes plastic deformation during final assembly.
Material, thickness and bend geometry should therefore support the intended forming operation.
Poorly controlled bending can cause:
cracking;
tearing;
excessive local deformation;
coating damage.
Where bending is function-critical, the intended forming method should be considered during component design.
A typical installation sequence may be:
Verify size, geometry, material and orientation.
Where applicable, engage the internal tongue or external locating tab with the intended stationary feature.
Bring the nut or bolt to the required assembly condition.
Identify the correct locking feature.
Bend the designated tab against the nut, bolt or locking feature according to the assembly design.
Verify that the locking path is properly established and that the tab is not visibly cracked or incorrectly positioned.
Not casually.
Backing off a tightened nut can alter the intended joint condition.
If tab alignment is difficult, the design or approved assembly procedure should address the issue.
Multi-tab designs or alternative tab positions can sometimes provide greater alignment flexibility.
Reuse should not be assumed.
A tab is plastically deformed during installation.
Removal and rebending can introduce:
work hardening;
cracking;
geometry changes;
reduced mechanical integrity.
For many maintenance applications, replacing the washer after disassembly can provide a more controlled locking condition.
Tab washers offer a useful visual indication of mechanical locking.
Inspection may verify:
correct washer type;
correct orientation;
engagement of locating features;
tab position;
contact with the intended reaction surface;
absence of visible cracks.
However, visual inspection cannot independently confirm correct original fastener preload.
Certain shaft and bearing arrangements use purpose-designed locking washers together with compatible locknuts.
An internal tongue may engage a shaft keyway while an external tab engages the nut.
These components should be selected as a compatible system.
A generic tab washer should not automatically replace a purpose-designed bearing lock washer.
Gearboxes can contain threaded shaft assemblies requiring mechanical rotational restraint.
Metric tab washers may be appropriate where:
the washer can be positively located;
the nut can be mechanically locked;
installation access exists;
the locking method is approved for the assembly.
Pumps, compressors and rotating industrial equipment can contain serviceable threaded assemblies.
Where tab washers are specified, engineers should consider:
vibration;
operating temperature;
corrosion;
service interval;
installation access.
Metric tab washers can be used in suitable:
machine tools;
drive systems;
material handling equipment;
mechanical actuators;
industrial processing equipment.
Custom tabs can be designed around machine-specific housings and brackets.
Heavy equipment can expose mechanical assemblies to vibration, shock, contamination and corrosion.
Positive mechanical locking can be useful for suitable threaded joints where the complete locking path is properly designed.
Mechanical assemblies within power-generation and electrical infrastructure equipment may require controlled fastener locking.
Material, finish and washer architecture should be selected according to the equipment specification and operating environment.
Fans, actuators, drives and mechanical equipment within HVAC systems can contain threaded assemblies requiring rotational restraint.
Environmental factors can include:
condensation;
temperature cycling;
vibration;
corrosion.
The washer should be selected accordingly.
Transportation equipment can use metric tab lock washers in appropriate mechanical assemblies.
Application-specific drawings, material requirements, traceability and validation should govern selection.
A generic industrial washer should not be promoted as suitable for every automotive, rail or aerospace joint.
A generic tab washer should not be described as an aerospace fastener merely because positive mechanical locking can be used in aerospace engineering.
Aircraft hardware can be governed by specific:
standards;
approved part numbers;
material requirements;
traceability;
qualification;
maintenance procedures.
JUXIN FASTENERS should only claim compliance or suitability when the actual part and documentation support it.
Custom tab washers can be developed where a standard configuration does not fit the assembly.
Potential customization includes:
metric bore size;
outside diameter;
material thickness;
internal tongue;
long external tab;
short locking tab;
multiple tabs;
angular position;
special slots;
material;
surface treatment.
The surrounding components should be included in the engineering review whenever possible.
Procurement teams sometimes need to replace an obsolete or difficult-to-source tab washer.
A replacement project should compare more than nominal diameter.
Important characteristics can include:
washer thickness;
internal profile;
locating feature;
tab dimensions;
tab position;
material;
finish;
mating nut;
shaft or housing geometry.
A visually similar washer is not necessarily functionally interchangeable.
Where no drawing exists, JUXIN FASTENERS can evaluate a physical sample together with assembly information.
An unused sample is preferable because previously bent tabs may no longer represent the original geometry.
Useful supporting information includes:
mating nut or bolt;
shaft dimensions;
housing geometry;
photographs of installed position;
material requirement;
annual demand.
Use this sequence when selecting a metric tab lock washer.
Determine exactly what component must be locked.
Find the structural feature that can react against washer rotation.
Determine whether the application requires:
long tab;
double tab;
internal tongue;
external tab;
multi-tab;
custom geometry.
Confirm:
stationary structure → washer → fastener
Verify that the washer can be positioned and the locking tab formed after tightening.
Match forming behavior and environmental requirements.
Determine whether the washer should be replaced after service disassembly.
For function-critical applications, evaluate the locking system under representative operating conditions.
For efficient engineering review and quotation, provide:
applicable drawing or specification;
metric fastener size;
nut or bolt type;
shaft dimensions where applicable;
keyway or slot dimensions where applicable;
washer inside diameter;
washer outside diameter;
thickness;
tab dimensions;
tab positions;
material;
surface finish;
stationary reaction feature;
application;
operating environment;
order quantity;
annual demand;
inspection requirements;
packaging requirements.
For custom or replacement parts, provide assembly drawings or photographs where possible.
It is a metric locking washer incorporating one or more mechanical features used to restrict unwanted rotation of a compatible threaded fastener.
A tab, tongue or lug connects the washer mechanically to the fastener and a stationary reaction feature, creating rotational restraint.
No. Their primary locking mechanisms are different.
A conventional tab lock washer should not be treated as a sealing component unless the specific design has been engineered for that function.
A single-tab design uses one primary tab architecture, while a double-tab washer can use two features for separate locating and locking functions.
It is a washer with an internal feature that can engage a compatible shaft keyway or slot to restrain washer rotation.
Reuse should not automatically be assumed because bending and rebending can alter the locking tab.
Yes. Dimensions, internal features, tab geometry, material and finish can be developed around the OEM assembly.
Not necessarily. Nominal size alone does not establish functional interchangeability.
Ideally, send the original drawing or specification. If unavailable, provide an unused sample, mating fastener information, assembly photographs and annual quantity.
Yes. JUXIN FASTENERS supports drawing-based and sample-based development of custom stamped washers and locking components for industrial OEM applications.
Metric tab lock washers should not be selected simply by asking:
"Which washer fits an M10, M16 or M20 fastener?"
The more useful engineering question is:
"How will the washer create a complete mechanical locking path between the threaded fastener and a stationary part of the assembly?"
That distinction separates dimensional fit from functional locking.
For design engineers, the fastener, washer and reaction feature should be evaluated as one system.
For procurement and supplier-development teams, the original drawing, mating-component information and application requirements help prevent false cross-references based only on nominal dimensions.
JUXIN FASTENERS supports global OEM, ODM, engineering, procurement,
sourcing and supplier-development teams with standard and custom metric tab lock washers, locking washers, stamped components and application-specific fasteners.
For an existing standard or drawing-controlled component, send the drawing or specification.
For a replacement component without a drawing, send an unused sample where possible together with mating-component and assembly information.
For new OEM development, provide the fastener type, stationary reaction geometry, tab configuration, material, finish, application and estimated annual demand.
We can support technical review, sample evaluation, cross-reference analysis, manufacturing feasibility review, custom development, quotation and volume production sourcing.
Email: info@juxinfasteners.com
Website: www.juxinfasteners.com
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