KM Bearing Lock Nuts | DIN 981 Slotted Shaft Locknuts

KM Bearing Lock Nuts for Precision Shaft and Bearing Retention

DIN 981 / ISO 2982-2 Slotted Bearing Nuts and Custom Shaft Locknuts

Juxin Fasteners manufactures KM bearing lock nuts, slotted shaft retaining nuts and custom precision threaded components for industrial bearing and power transmission assemblies.

Bearing lock nuts are used to axially position and secure rolling bearings, adapter sleeves, gears, bushings and other components mounted on threaded shafts.

Unlike conventional hexagonal locknuts, these round nuts feature external slots designed for engagement with a hook spanner or compatible spanner socket.

KM-series bearing lock nuts are commonly associated with DIN 981 and ISO 2982-2 dimensional references. They are often used with compatible tab lock washers to prevent unintended rotation after tightening.

Juxin Fasteners supports carbon steel and stainless steel versions, including custom dimensions and made-to-drawing manufacturing for international OEM customers.

Product Specifications

Not every size or thread form is available in every product family. Standard compliance and manufacturing availability must be verified for each part number.

What Is a Bearing Lock Nut?

A bearing lock nut is a precision threaded retaining component used to control the axial position of a bearing or another shaft-mounted element.

It is normally installed on a threaded shaft or adapter sleeve.

The nut is tightened against the appropriate bearing ring, spacer or mating component to establish the required axial location.

A compatible locking device can then be used to prevent the nut from rotating during operation.

Bearing lock nuts are commonly used in:

• Rolling bearing assemblies

• Machine tool spindles

• Electric motor shafts

• Industrial gearboxes

• Power transmission equipment

• Mechanical drive systems

• Pump and compressor assemblies

The correct nut must match the shaft thread, bearing arrangement and locking accessory.

DIN 981 and ISO 2982-2 Bearing Lock Nuts

DIN 981 is a widely recognized reference for bearing lock nuts.

ISO 2982-2 provides international dimensional specifications for relevant bearing accessory lock nuts and locking devices.

These standards help engineers identify compatible dimensions and bearing mounting components.

The actual product must be checked against the specified standard edition and dimensional requirements before compliance is claimed.

KM, KML and HM Bearing Lock Nut Families

Different bearing lock nut families are designed for different shaft sizes, thread forms and bearing arrangements.

They should not be treated as interchangeable products.

The shaft thread, nut series and locking device must be selected together.

Important Thread Distinction

KM and KML lock nuts commonly use ISO metric threads.

Certain HM-family bearing lock nuts use metric trapezoidal threads.

These thread systems have different profiles and cannot be interchanged.

The exact thread form must be verified from the relevant bearing manufacturer catalog or engineering drawing.

How Bearing Lock Nuts Secure Bearings

1. Shaft Preparation

The shaft or adapter sleeve must have the specified thread, locating features and suitable bearing mounting surfaces.

2. Bearing Installation

The bearing is installed according to the approved mounting procedure.

3. Nut Engagement

The lock nut is threaded onto the shaft or sleeve.

A suitable hook spanner or spanner socket is used to tighten the nut.

4. Axial Positioning

The nut is tightened according to the bearing arrangement and mounting requirements.

For certain bearing arrangements, axial displacement or bearing clearance reduction may be part of the installation procedure.

5. Mechanical Locking

Where specified, a compatible tab lock washer is used to prevent rotation.

The locking method must match the shaft and nut design.

6. Final Inspection

The assembly is checked for correct positioning, locking-device engagement and any specified bearing clearance or mounting condition.

Mechanical Locking with MB Tab Washers

KM bearing lock nuts are commonly paired with MB-series locking washers.

These washers are different from conventional split spring washers.

A typical tab washer arrangement includes:

• An internal tab engaging the shaft keyway.

• External tabs positioned around the washer circumference.

• An external tab bent into a suitable nut slot after tightening.

This creates a positive mechanical connection between the shaft and nut.

The washer prevents relative rotation through mechanical engagement rather than relying only on friction.

The washer must be the correct type and size for the nut and shaft.

DIN 5406 Lock Washer Compatibility

DIN 5406 is an important reference for locking washers used with bearing lock nuts.

However, washer compatibility must be checked by product family.

A washer intended for a KM nut is not automatically compatible with every KML or HM design.

The washer's internal tab, outside diameter, thickness and external tab arrangement must match the intended assembly.

Slotted Design for Spanner Installation

The external slots allow a suitable tool to engage the round nut.

Typical tools include:

• Hook spanners

• C-spanners

• Bearing locknut sockets

• Special OEM assembly tools

The number and dimensions of the slots depend on the nut series and size.

The photographed product has external spanner slots, but the exact number and dimensional standard must be confirmed from the drawing.

Metric Bearing Lock Nut Sizes

The following table provides common KM-series metric thread references.

These are common catalog references, not a complete dimensional table.

The thread pitch, outside diameter, nut width, slot dimensions and matching washer must be verified for each designation.

Larger bearing lock nuts are available in established industrial series, but designation and dimensional compatibility require individual verification.

Large-Diameter Bearing Lock Nuts

Industrial bearing assemblies may require significantly larger retaining nuts.

The broad reference range of M10 to M280 covers multiple bearing lock nut designs rather than a single interchangeable KM series.

Large-diameter designs may require:

• Different thread forms

• Different nut widths

• Special spanner arrangements

• Alternative locking washers

• Higher tightening forces

• Special machining equipment

• Defined face runout tolerances

Juxin Fasteners evaluates large-diameter custom manufacturing requirements according to drawings and production feasibility.

Inch Dimension References for International Buyers

North American engineering teams may use inch measurements when reviewing metric bearing lock nuts.

The following conversions are dimensional references only.

These conversions do not establish an equivalent inch-thread specification.

Metric bearing lock nut threads cannot be directly replaced with UNC or UNF threads.

Custom Inch-Thread Shaft Retaining Nuts

Some North American OEM projects use Unified inch threads or other shaft-specific thread systems.

Juxin Fasteners can evaluate custom slotted retaining nuts with customer-specified inch threads.

Potential design references include:

• 1/2-20 UNF

• 5/8-18 UNF

• 3/4-16 UNF

• 7/8-14 UNF

• 1-12 UNF

• 1 1/4-12 UNF

These are examples of Unified thread designations for custom engineering consideration, not standard DIN 981 KM sizes.

Actual suitability depends on the shaft geometry, thread class, nut dimensions and locking arrangement.

Carbon Steel Bearing Lock Nuts

Carbon steel is widely used for industrial bearing retaining nuts.

It can provide suitable mechanical strength and wear resistance for many machinery applications.

Material selection should consider:

• Required mechanical properties

• Machinability

• Thread strength

• Operating loads

• Corrosion exposure

• Surface treatment

• Production quantity

The specific steel grade should be established from the engineering drawing.

Stainless Steel Bearing Lock Nuts

Stainless steel may be selected for bearing assemblies exposed to moisture or other corrosive environments.

Potential grades for engineering evaluation include 304 and 316 stainless steel.

304 stainless steel is suitable for many general industrial environments.

316 stainless steel generally offers improved resistance to certain chloride-containing environments.

However, corrosion resistance depends on the actual service conditions.

Stainless steel threads may also require consideration of galling, especially during repeated installation.

Surface Treatment Options

Depending on material and customer requirements, surface treatments may include:

• Zinc plating for suitable carbon steel parts

• Black oxide

• Phosphate coating

• Stainless steel passivation

• Other customer-approved treatments

Surface finish requirements must account for thread fit, corrosion protection and bearing assembly compatibility.

Precision Bearing Positioning

Bearing lock nuts are important in assemblies where axial positioning affects equipment performance.

The relevant design parameters may include:

• Thread accuracy

• Locating-face perpendicularity

• Axial runout

• Nut width

• Bearing contact geometry

• Tightening procedure

• Shaft alignment

Poorly controlled dimensions or incorrect installation may affect bearing operation.

Precision requirements must be defined according to the bearing arrangement.

Machine Tool Spindle Applications

Machine tool spindles require controlled bearing mounting and axial positioning.

Bearing lock nuts may be used to retain spindle bearings and related shaft-mounted components.

Critical considerations include:

• Axial location

• Bearing preload or clearance

• Locating-face accuracy

• Rotational speed

• Thermal expansion

• Assembly procedures

High-speed spindle applications require particular attention to accuracy and balance.

Industrial Gearbox Applications

Gearboxes contain shafts, bearings, gears and spacers that require reliable axial retention.

Bearing lock nuts may be used in selected gearbox arrangements.

Engineers should evaluate:

• Shaft loads

• Bearing type

• Lubrication

• Vibration

• Operating temperature

• Locking washer compatibility

The nut and locking device must be suitable for the complete transmission design.

Electric Motors and Industrial Drives

Electric motors and drive systems may use bearing lock nuts to secure bearings and other shaft-mounted components.

Potential applications include:

• Industrial motor assemblies

• Mechanical drive shafts

• Gear motor systems

• Coupling assemblies

• Auxiliary power transmission equipment

The installation must follow the equipment manufacturer's bearing mounting requirements.

Pumps and Compressors

Pumps and compressors often incorporate rotating shafts and bearing assemblies.

Bearing retaining nuts may be used where axial positioning and serviceability are required.

Material and dimensional requirements depend on the equipment design, fluid exposure and operating conditions.

Wind Energy and Power Generation

Power generation equipment may include large bearings and mechanical transmission systems.

Potential applications include:

• Gearbox bearing assemblies

• Auxiliary drive systems

• Rotating machinery

• Industrial generator equipment

Large-diameter lock nuts require careful consideration of thread geometry, tightening methods and mechanical retention.

Application suitability must be validated by the equipment manufacturer.

Rail Transit Equipment

Rail transit machinery includes motors, gearboxes and other rotating mechanical assemblies.

Bearing lock nuts may be considered for appropriate shaft-retention applications.

The complete assembly must meet the relevant rail equipment requirements.

No rail-industry qualification is implied by the nut's geometry alone.

Mining and Heavy Machinery

Mining and heavy industrial equipment may use large bearings in demanding operating environments.

Bearing lock nuts can be used for selected shaft-retention arrangements.

Engineers should consider:

• Heavy mechanical loads

• Vibration and shock

• Dust and contamination

• Maintenance access

• Corrosion protection

• Locking-device reliability

The appropriate nut and washer must be selected according to the equipment design.

Marine and Offshore Machinery

Marine machinery may require corrosion-resistant bearing retention components.

Stainless steel can be considered for selected applications, but the material must be compatible with the actual exposure conditions.

Marine environments can produce pitting and crevice corrosion even in stainless steel.

Material selection should not be based on stainless steel designation alone.

Food Processing and Chemical Equipment

Some food-processing and chemical equipment uses rotating shafts and bearing assemblies.

Stainless steel bearing lock nuts may be evaluated where corrosion resistance is important.

The selection must consider cleaning procedures, chemical exposure and equipment hygiene requirements.

No food-contact or chemical compatibility certification is implied.

Custom Manufacturing Capabilities

Juxin Fasteners supports made-to-drawing manufacturing of industrial shaft retaining nuts and precision metal components.

Depending on the product design, operations may include:

• CNC turning

• Internal threading

• External profile machining

• Slot milling

• Chamfering

• Face machining

• Surface finishing

• Dimensional inspection

For appropriate designs, manufacturing may also incorporate cold forming or other suitable production processes.

The final process route depends on material, dimensions, tolerances and order quantity.

Custom Bearing Lock Nut Designs

Juxin Fasteners can evaluate customer-specific designs with:

• Custom thread diameter

• Special thread pitch

• Metric fine threads

• Metric trapezoidal threads

• Customer-specified inch threads

• Modified outside diameter

• Custom nut width

• Special slot geometry

• Modified locating face

• Material-specific designs

• Special surface finishes

• Customer part identification

Nonstandard designs require an approved engineering drawing.

Quality Control and Inspection

Depending on the approved specification, inspection may include:

• Material verification

• Thread gauging

• Outside diameter measurement

• Nut width inspection

• Slot dimensions

• Locating-face runout

• Thread-to-face perpendicularity

• Surface finish

• Coating verification

• Functional fit with the shaft

• Compatibility with the specified locking washer

Inspection methods and acceptance criteria must be agreed upon before production.

Relevant International Standards

The applicability of each standard depends on the exact nut series, thread form and customer specification.

Frequently Asked Questions

What is a KM bearing lock nut?

A KM bearing lock nut is a round threaded nut with external spanner slots, commonly used for axial retention of bearings and other shaft-mounted components.

Are KM lock nuts the same as ordinary self-locking nuts?

No. Standard KM bearing lock nuts generally rely on a separate locking device, such as a compatible tab washer, rather than an integral prevailing-torque mechanism.

What is the difference between KM and KML lock nuts?

They belong to related bearing lock nut families but have different dimensional characteristics. Selection requires checking the exact series and bearing arrangement.

Are HM lock nuts interchangeable with KM lock nuts?

No. Certain HM designs use metric trapezoidal threads and different dimensions.

What is DIN 981?

DIN 981 is a recognized dimensional reference for bearing lock nuts.

What is ISO 2982-2?

It is an international standard covering relevant rolling bearing accessory lock nuts and locking devices.

What is the function of an MB lock washer?

A compatible MB tab washer mechanically prevents rotation by engaging the shaft keyway and a slot in the lock nut.

Can a KM lock nut be installed without a washer?

The installation method depends on the complete bearing assembly. A locking device should not be omitted where specified.

What tool is used to tighten a bearing lock nut?

A suitable hook spanner, C-spanner or bearing locknut socket is commonly used.

Can Juxin Fasteners manufacture stainless steel bearing lock nuts?

Yes. Stainless steel designs can be evaluated according to the required grade, dimensions and production specifications.

Can Juxin Fasteners manufacture large-diameter lock nuts?

Large-diameter custom manufacturing inquiries can be evaluated according to engineering drawings and manufacturing feasibility.

Can inch-thread versions be manufactured?

Custom inch-thread shaft retaining nuts can be evaluated, but they are not directly interchangeable with metric DIN 981 designs.

Are these nuts suitable for high-speed spindles?

Suitability depends on locating-face accuracy, bearing arrangement, balance and operating conditions.

Can the nut be customized for an existing bearing assembly?

Yes. Juxin Fasteners supports drawing-based OEM/ODM manufacturing of custom bearing retaining components.

Request a Quote — KM Bearing Lock Nuts and Custom Shaft Retaining Nuts

Juxin Fasteners is an industrial fastener manufacturer supporting international OEM, Tier-1 and Tier-2 manufacturing programs.

We manufacture custom metal fasteners and precision threaded components using CNC machining, suitable forming processes and secondary operations.

Our engineering and manufacturing services support KM bearing lock nuts, slotted shaft nuts and custom bearing retaining components.

Recommended RFQ Information

• 2D engineering drawing or 3D CAD model

• Customer part number

• Bearing lock nut series: KM, KML, HM or custom

• Applicable standard

• Shaft thread designation

• Thread diameter and pitch

• Thread tolerance

• Outside diameter

• Nut width

• Slot quantity and dimensions

• Locating-face requirements

• Runout tolerance

• Material grade

• Surface treatment

• Matching bearing designation

• Matching locking washer designation

• Shaft or adapter sleeve information

• Required inspection criteria

• Initial order quantity

• Estimated annual demand

• Packaging requirements

• Required delivery schedule

Please send your drawings, samples or technical specifications for manufacturing feasibility review and quotation.

Juxin Fasteners

Industrial Fastener Manufacturer | KM Bearing Lock Nuts | DIN 981 Shaft Locknuts | Custom CNC Machined Bearing Retaining Nuts

Website: https://www.juxinfasteners.com/

Email: info@juxinfasteners.com

Packaging Standard

At Juxin Fasteners, we apply standardized export packaging to ensure product protection, traceability, and compliance with international logistics requirements.

1. Standard Export Packaging

Unless otherwise specified, all products will be packed according to our factory standard export packaging, which includes:

Moisture-resistant inner protection

Poly bag or small box packing as required

Reinforced export cartons

Clear labeling with part number, specification, batch number, and quantity

Palletizing for sea or air shipment when necessary

Our standard packaging is designed to ensure safe transportation, efficient warehousing, and long-distance international shipping.

2. Customized Packaging Options

We also provide customized packaging solutions according to customer requirements, including but not limited to:

Private labeling

Customized barcodes

Specific carton dimensions

Retail packaging

Special pallet configuration

Customer-specific marking and identification

So that you know, customized packaging may involve additional costs and extended lead time depending on the complexity of the requirements.

3. Compliance & Quality Assurance

All packaging processes are controlled under our ISO 9001 quality management system to ensure consistency, traceability, and product integrity throughout the supply chain.