GUK Nylon Insert Bearing Locknuts for Shaft Retention

GUK Nylon Insert Bearing Locknuts for Shaft Retention

Custom Self-Locking Round Nuts for Bearings, Gearboxes, Spindles and Industrial Power Transmission

Juxin Fasteners manufactures GUK-style nylon insert bearing locknuts for threaded shafts, bearing assemblies and industrial power transmission systems.

These round locknuts combine a metal body, peripheral wrenching slots and a nonmetallic locking insert. The nylon insert engages the mating shaft thread to generate prevailing torque, helping resist unintended rotation and loosening.

GUK nylon insert locknuts are commonly used in applications related to the KM bearing locknut family. However, the additional locking insert changes their functional characteristics and must be considered when selecting the correct component.

Juxin Fasteners supports OEM/ODM manufacturing of standard-style and custom-engineered bearing locknuts based on customer drawings, material specifications, tolerances and production requirements.

Product Specifications

Dimensions, locking performance, materials and finishes must be confirmed against the approved drawing.

What Is a GUK Nylon Insert Bearing Locknut?

A GUK nylon insert bearing locknut is a round shaft nut with a nonmetallic locking insert.

Unlike a conventional round bearing locknut that relies on a separate mechanical locking device, the GUK design incorporates an insert that creates friction against the mating shaft thread.

This resistance is known as prevailing torque.

The locking feature is intended to resist unintended rotation after installation.

The nut may be used to retain or position suitable bearings and other components on a threaded shaft.

How the Nylon Insert Locking Mechanism Works

As the nut is threaded onto the shaft, the mating external thread engages and deforms the nylon insert.

The elastic response of the insert produces frictional resistance against rotation.

This prevailing torque remains relevant even when the nut is not fully clamped against another component.

However, the locking insert does not eliminate the need to establish the correct axial position, clamping force or bearing mounting procedure.

Locking performance depends on:

• Nylon grade and geometry.

• Shaft thread dimensions.

• Thread tolerance.

• Nut installation condition.

• Operating temperature.

• Contamination and lubrication.

• Number of installation cycles.

• Vibration and loading conditions.

The prevailing torque must be verified where it is a critical engineering requirement.

GUK Series and KM Bearing Locknuts

GUK nylon insert locknuts are closely related to conventional KM-series bearing locknuts.

Both use round bodies with peripheral slots and metric fine threads.

The important distinction is the locking method.

GUK and KM components should not be substituted without checking dimensions, locking requirements and assembly design.

GUK Metric Fine-Thread Size References

The following sizes correspond to commonly published GUK-series references.

This table is an industry reference series, not a declaration that every size is currently stocked.

The supplied product information also includes M20 × 1.5 and M90 × 5.0. These must be treated as separate custom-thread inquiries unless the actual product drawing confirms otherwise.

Other custom sizes and pitches can be evaluated according to manufacturing feasibility.

Metric Fine Threads and Shaft Compatibility

GUK bearing locknuts commonly use metric fine threads.

A fine-thread designation must include both nominal diameter and pitch.

For example:

• M20 × 1.0 is different from M20 × 1.5.

• M90 × 2.0 is different from M90 × 5.0.

A nut must match the shaft's actual thread dimensions and tolerance.

The nominal diameter alone is insufficient to establish compatibility.

Inch Dimension References

North American engineers may use the following approximate inch conversions when reviewing metric GUK sizes.

These are diameter conversions only.

They do not represent interchangeable Unified inch-thread sizes.

Custom Inch-Thread Shaft Locknuts

North American bearing and power transmission applications may use Unified inch threads.

Depending on the shaft design, potential custom thread references include:

• 3/4-16 UNF.

• 1-12 UNF.

• 1-1/4-12 UNF.

• 1-1/2-12 UNF.

These are engineering examples for custom evaluation, not GUK standard sizes or confirmed available products.

The thread diameter, pitch, thread class, nut geometry and locking insert must be reviewed as a complete design.

Metric GUK locknuts are not directly interchangeable with Unified inch-thread bearing locknuts.

Carbon Steel GUK Locknuts

Carbon steel is commonly selected for industrial shaft locknuts because it offers useful strength and manufacturing properties.

The selected grade should be based on the mechanical requirements of the assembly.

Relevant considerations include:

• Thread strength.

• Bearing contact pressure.

• Wear resistance.

• Machinability.

• Surface protection.

• Dimensional stability.

The material grade and any required heat treatment must be specified in the approved drawing.

Stainless Steel GUK Locknuts

Stainless steel versions may be evaluated where corrosion resistance is important.

Potential material references include suitable stainless steel grades selected according to the application.

Important engineering considerations include:

• Corrosion exposure.

• Thread galling.

• Material strength.

• Surface condition.

• Compatibility with the shaft material.

• Operating temperature.

• Manufacturing feasibility.

Stainless steel body selection does not eliminate the temperature and chemical limitations of the nylon insert.

Nylon and Polyamide Insert Selection

The locking insert is a critical functional component.

Its performance depends on the selected polymer grade and the geometry of the insert.

Important requirements may include:

• Material identification.

• Dimensional consistency.

• Prevailing torque.

• Temperature resistance.

• Chemical compatibility.

• Aging behavior.

• Reuse performance.

Polyamide materials may be used for this locking function, but the specific grade must be confirmed.

Operating Temperature

Published GUK product catalogs commonly identify a maximum operating temperature around 100°C for certain polyamide insert configurations.

This must not be treated as a universal rating for every nylon insert locknut.

The actual operating limit depends on the polymer grade, operating environment, exposure duration and required locking performance.

Applications exceeding the validated temperature limit require a different locking solution.

Can GUK Locknuts Be Reused?

A nylon insert locknut may retain locking resistance after removal, but reuse is not unlimited.

Repeated installation can change the prevailing torque.

The allowable number of installation cycles should be determined by the applicable product specification or OEM test requirements.

No universal three-cycle, five-cycle or other reuse guarantee is claimed.

Bearing Axial Retention

GUK nylon insert bearing locknuts may be used to retain suitable bearing components on threaded shafts.

The nut helps maintain the intended axial position while its locking insert resists loosening.

Correct bearing mounting requires consideration of:

• Bearing arrangement.

• Shaft shoulder geometry.

• Axial load.

• Thread engagement.

• Contact surface.

• Installation torque.

• Locking torque.

• Operating speed.

• Thermal expansion.

The locking nut alone does not determine the allowable bearing preload.

Gearbox and Speed Reducer Applications

Gearbox manufacturers may use shaft locknuts to position bearings and selected transmission components.

Relevant considerations include:

• Shaft vibration.

• Axial loading.

• Lubrication.

• Operating temperature.

• Assembly accessibility.

• Thread accuracy.

• Locking reliability.

GUK-style locknuts can be evaluated where their prevailing-torque mechanism is compatible with the gearbox design.

Machine Tool Spindles

Machine tool spindle assemblies may require accurate bearing positioning and controlled axial retention.

GUK-style nuts may be considered for suitable applications, but they should not automatically be treated as precision bearing preload nuts.

High-precision spindle applications may require specialized locknuts with tighter axial runout and face perpendicularity requirements.

The appropriate nut must be selected according to the spindle's bearing arrangement and accuracy requirements.

Electric Motors and Industrial Drives

Bearing retention is an important design consideration in motors, pumps and industrial drives.

GUK nylon insert shaft nuts may be evaluated where operating temperature, vibration, shaft geometry and installation requirements are suitable.

Pumps and Compressors

Selected pump and compressor shaft assemblies may use threaded retaining components.

The nut must be evaluated for:

• Rotational speed.

• Temperature.

• Vibration.

• Lubrication.

• Axial loading.

• Maintenance access.

The presence of a nylon insert does not establish suitability for every compressor or pump environment.

Agricultural and Construction Machinery

Industrial machinery exposed to vibration may require suitable shaft retention systems.

Applications may include selected bearing housings, gearboxes and rotating assemblies.

Material selection and locking requirements must reflect the actual operating loads and environmental conditions.

Automotive and Transportation Equipment

Bearing retaining nuts are used in various vehicle and transportation assemblies.

A GUK-style nylon insert locknut may be considered where the OEM design specifically permits this type of locking mechanism.

Safety-critical automotive, rail and aerospace applications require their own engineering validation, qualification and approval.

No universal suitability for these applications is claimed.

Installation Using a Hook Spanner or Locknut Socket

GUK-style round nuts typically have peripheral grooves for suitable installation tooling.

Depending on the nut size and groove geometry, installation may use:

• Hook spanners.

• Bearing locknut sockets.

• Other approved assembly tooling.

The correct tool should engage the nut securely without damaging the grooves.

Installation procedures should follow the equipment manufacturer's requirements.

Prevailing Torque vs. Tightening Torque

Prevailing torque is the resistance generated by the locking mechanism during rotation.

Tightening torque is the applied torque used to establish the required joint condition.

These values are related but not identical.

For bearing assemblies, the engineer must consider both the locking resistance and the torque needed for the intended axial positioning.

The presence of a nylon insert must not be used as a substitute for proper bearing mounting calculations.

When a Lock Washer May Be Unnecessary

The integrated nylon insert may eliminate the need for a separate lock washer in some compatible designs.

However, it should not be assumed that a GUK nut can replace every KM nut and locking washer arrangement.

The assembly must be reviewed for:

• Axial retention.

• Prevailing torque.

• Vibration.

• Shaft rotation.

• Temperature.

• Maintenance requirements.

• Applicable design standards.

Round Nut Geometry and Wrenching Grooves

Important dimensions include:

• Thread diameter and pitch.

• Outside diameter.

• Nut height.

• Bearing contact face.

• Groove width.

• Groove depth.

• Number of grooves.

• Nylon insert dimensions.

• Thread engagement length.

These features affect installation, tool compatibility and functional performance.

CNC Machining and Custom Manufacturing

Juxin Fasteners supports precision CNC machining and other appropriate manufacturing operations for custom metal fastening components.

For GUK-style bearing locknuts, manufacturing may involve:

• Body machining.

• Internal thread machining.

• Groove machining.

• Face finishing.

• Surface treatment.

• Locking insert assembly.

• Dimensional inspection.

The actual process route depends on the material, geometry, production quantity and approved manufacturing plan.

Cold heading and cold forming may be considered for suitable components, but they are not assumed to be the manufacturing method for every GUK-style nut.

Custom OEM Bearing Locknuts

Juxin Fasteners supports made-to-drawing bearing locknut projects.

Customization may include:

• Nonstandard metric fine threads.

• Custom Unified inch threads.

• Special outside diameters.

• Modified nut heights.

• Different groove configurations.

• Special bearing contact faces.

• Carbon steel or stainless steel bodies.

• Customer-specified finishes.

• Custom locking insert materials.

• Special dimensional tolerances.

• Functional testing requirements.

All modifications require engineering and manufacturing feasibility review.

Dimensional Inspection and Functional Testing

Depending on the project, inspection requirements may include:

• Material verification.

• Thread gauging.

• Outside diameter.

• Nut height.

• Groove geometry.

• Bearing contact face.

• Surface finish.

• Insert position.

• Prevailing torque.

• Functional installation.

• Batch acceptance criteria.

Specific performance limits should be established in the customer specification.

Common Engineering Risks

Insufficient Prevailing Torque

Incorrect insert dimensions, polymer degradation or excessive reuse may reduce locking resistance.

Incorrect Thread Pitch

A nut with the wrong pitch can damage the shaft thread or fail to engage properly.

Excessive Installation Torque

Overtightening may damage threads, bearing components or adjacent parts.

Thermal Degradation

Operating temperatures beyond the validated limit may affect the locking insert.

Thread Galling

Stainless steel combinations may require special attention to lubrication and surface conditions.

Bearing Preload Errors

Incorrect axial positioning or tightening procedures may adversely affect bearing performance.

Improper Tool Engagement

Unsuitable tools can damage the peripheral wrenching grooves.

Purchasing and Supplier Development

OEM procurement and supplier development teams should evaluate:

• Correct GUK reference.

• Thread diameter and pitch.

• Material grade.

• Surface finish.

• Nylon insert specification.

• Dimensional tolerances.

• Prevailing torque requirements.

• Inspection criteria.

• Sample approval.

• MOQ.

• Tooling requirements.

• Production lead time.

• Annual demand.

• Packaging requirements.

MOQ, pricing and delivery schedules are determined from the actual project requirements.

Relevant International Standards

The following references may be relevant depending on the approved design:

• ISO 261: ISO metric screw-thread general plan.

• ISO 724: Basic dimensions of ISO metric screw threads.

• ISO 965 Series: ISO metric screw-thread tolerances.

• ISO 2982 Series: Bearing accessories, including dimensions of relevant locknuts and locking devices.

• DIN 981: Historical and industry dimensional reference for bearing locknuts.

• ASME B1.1: Unified inch screw threads for custom inch-thread designs.

• ISO 2320: Prevailing-torque steel nuts, where its scope and applicability to the particular design are confirmed.

GUK-style nylon insert locknuts may follow dimensions associated with conventional bearing locknuts, but conformity to a specific standard must be verified.

Frequently Asked Questions

What is a GUK nylon insert bearing locknut?

It is a slotted round shaft locknut with an integrated nonmetallic insert that generates prevailing torque against the mating shaft thread.

What is the difference between GUK and KM locknuts?

GUK-style nuts incorporate a nylon locking insert, while conventional KM locknuts generally use a separate mechanical locking arrangement.

What sizes are commonly associated with the GUK series?

Published GUK references commonly cover M10 × 0.75 through M100 × 2.0.

Is M20 × 1.0 interchangeable with M20 × 1.5?

No. They have different thread pitches.

Is M90 × 5.0 a standard GUK18 thread?

The commonly published GUK18 reference is M90 × 2.0. M90 × 5.0 requires separate drawing verification.

Can GUK nuts be manufactured in stainless steel?

Stainless steel versions can be evaluated according to material, dimensions and manufacturing requirements.

Can GUK locknuts be reused?

Reuse depends on retained prevailing torque and the applicable acceptance criteria.

Are GUK nuts suitable for high temperatures?

Their operating limit is restricted by the locking insert material and must be verified.

Do GUK locknuts always eliminate lock washers?

No. The suitability of the integrated locking mechanism must be established for the complete assembly.

Can GUK locknuts be used for precision spindle bearing preload?

Only when the nut's dimensional accuracy and locking characteristics meet the spindle manufacturer's requirements.

Are metric GUK threads interchangeable with inch bearing locknut threads?

No. Metric and Unified thread systems must be treated separately.

Can Juxin Fasteners manufacture custom GUK-style locknuts?

Yes. Juxin Fasteners supports custom-engineered bearing locknuts based on customer drawings and technical specifications.

Request a Quote — GUK Nylon Insert Bearing Locknuts

Juxin Fasteners is an industrial fastener manufacturer supporting OEM and custom-engineered fastening components for bearing manufacturers, 

gearbox manufacturers, machine builders and industrial power transmission OEMs.

Our manufacturing capabilities include cold heading, cold forming, CNC machining and suitable product-specific secondary operations.

Manufacturing processes are selected according to the approved drawing, material, tolerances and production requirements.

Recommended RFQ Information

• 2D engineering drawing or 3D CAD model.

• GUK reference or customer part number.

• Internal thread diameter and pitch.

• Outside diameter.

• Nut height.

• Groove number and dimensions.

• Bearing contact face requirements.

• Carbon steel or stainless steel grade.

• Surface finish.

• Nylon insert specification.

• Operating temperature.

• Shaft material.

• Prevailing torque requirements.

• Installation and removal requirements.

• Bearing arrangement and axial loading.

• Inspection and testing requirements.

• 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 | GUK Nylon Insert Bearing Locknuts | Custom Shaft Locknuts | OEM Bearing Fastener Manufacturing

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.