Husqvarna 539108366 1/2-13 x 4 Grade 5 Hex Cap Screw – Genuine OEM Replacement Bolt
Part Number: 539108366
Category: Lawn Mower, Outdoor Power Equipment & Replacement Hardware
Type: 1/2-13 x 4-Inch Grade 5 Hex Cap Screw – Genuine OEM Replacement Bolt
The Husqvarna 539108366 Hex Cap Screw is a genuine OEM replacement fastener designed for select Husqvarna lawn mowers, zero-turn mowers, lawn tractors, and compatible outdoor power equipment assemblies. This hardware is specified as a 1/2-13 x 4-inch Grade 5 hex cap screw, providing an application-specific fastening solution for equipment requiring Husqvarna part number 539108366.
Product Specifications
- Part Number: 539108366
- Manufacturer: Husqvarna
- Product Type: Hex Cap Screw
- OEM Description: HCS 1/2-13 x 4 GR 5
- Alternate Description: Hex Head Cap Screw / Hex Bolt / Equipment Mounting Bolt
- Nominal Diameter: 1/2 Inch
- Thread Specification: 1/2-13
- Threads Per Inch: 13 TPI
- Nominal Length: 4 Inches
- Strength Grade: Grade 5
- Thread Standard: UNC / Coarse Thread
- Head Style: Hex Head
- Component Type: Equipment Fastener / Mounting Hardware
- Primary Application: Outdoor Power Equipment
- System: Model & Assembly Dependent
- Function: Secures Compatible Equipment Components
- Compatible Brand: Husqvarna
- Installation Location: Model Dependent
- Associated Components: Nuts / Washers / Brackets / Mounting Assemblies
- Replacement Type: Direct OEM Replacement
- OEM Status: Genuine Husqvarna OEM Part
- Condition: New
- Quantity: 1 Hex Cap Screw
- Part Number Reference: 539108366
- Alternate Number Format: 539 10 83-66
Features & Benefits
- Genuine Husqvarna OEM replacement hardware
- Factory-specified 1/2-13 x 4-inch configuration
- Grade 5 strength classification
- Standard coarse-thread design
- 13 threads per inch
- Hex-head configuration for conventional tool engagement
- Designed for compatible Husqvarna equipment assemblies
- Provides secure mechanical fastening
- Application-specific OEM replacement
- Suitable for equipment repair, servicing, and restoration
- Appropriate replacement for bent, stripped, corroded, or missing hardware
- Maintains the original equipment fastener specification
- Direct replacement for applications specifying 539108366
1/2-13 Thread Specification
The 539108366 uses a 1/2-13 thread specification.
This designation means:
- 1/2 Inch: Nominal outside thread diameter
- 13: Number of threads per inch
The 1/2-13 configuration is a coarse-thread specification commonly used for mechanical fastening applications.
The mating nut or threaded component must use the same 1/2-13 thread pattern.
A fine-thread 1/2-inch fastener should not be substituted simply because the nominal diameter is the same.
4-Inch Nominal Length
The 539108366 has a nominal fastener length of 4 inches.
Correct bolt length is important because an improperly sized fastener may:
- Fail to provide sufficient thread engagement
- Extend too far through an assembly
- Contact surrounding components
- Interfere with moving parts
- Prevent correct installation
- Alter the clamping arrangement
For equipment specifying 539108366, use the OEM part number as the primary replacement reference.
Grade 5 Fastener
The 539108366 is specified as a Grade 5 fastener.
SAE Grade 5 bolts are commonly identified as medium-strength carbon-steel fasteners intended for mechanical applications requiring greater strength than standard low-strength hardware.
The grade specification is important because fasteners that look physically similar can have different mechanical properties.
Do not substitute a lower-strength bolt simply because its diameter, thread pitch, and length match.
Hex Head Design
The hexagonal head allows the fastener to be installed or removed using an appropriately sized:
- Socket
- Ratchet
- Wrench
- Torque wrench
Using the correct tool size helps reduce the possibility of rounding or damaging the bolt head.
Avoid using worn or incorrectly sized tools when removing tightly installed equipment hardware.
Equipment Applications
The 539108366 is used on select Husqvarna outdoor power equipment assemblies.
Depending on the exact model, a fastener of this type may be associated with structural, chassis, suspension, steering, deck, or other mechanical assemblies.
Because the installation location varies by equipment model, compatibility should be determined using the part number and applicable illustrated parts diagram, rather than assuming a specific mounting location based solely on the bolt dimensions.
Common Reasons for Replacement
Replacement of the 539108366 Hex Cap Screw may be appropriate if the original fastener has:
- Become bent
- Developed damaged threads
- Developed a rounded head
- Become heavily corroded
- Sustained impact damage
- Become stretched
- Developed excessive wear
- Been cross-threaded
- Been overtightened
- Become seized
- Been lost during equipment service
- Become unsuitable for safe reuse
A visibly damaged structural fastener should generally be replaced rather than reused.
Thread Inspection
Before installing the replacement bolt, inspect the mating threads.
Check for:
- Cross-threading
- Corrosion
- Dirt
- Damaged threads
- Metal debris
- Distortion
- Previous incorrect hardware
The new bolt should thread into the corresponding nut or threaded component correctly without requiring excessive force.
If significant resistance occurs immediately during installation, stop and verify the thread alignment and specification.
Washer Inspection
If the application uses a washer, inspect it for:
- Bending
- Cracking
- Excessive corrosion
- Distortion
- Enlarged center hole
- Excessive wear
Washers can help distribute clamping force across the mounting surface.
Reuse or replacement should follow the configuration specified for the equipment.
Nut Inspection
If 539108366 is secured with a separate nut, verify that the nut has the correct:
1/2-13 thread specification
Also inspect the nut for:
- Damaged threads
- Corrosion
- Distortion
- Cross-threading
- Damaged locking features where applicable
Do not force mismatched threads together.
Mounting Surface Inspection
Before installing the replacement fastener, inspect the components being secured.
Look for:
- Cracks
- Elongated mounting holes
- Bent brackets
- Corrosion
- Distorted metal
- Damaged bushings
- Missing spacers
- Excessive wear
Installing a new bolt will not correct an underlying problem with damaged mounting components.
Installation Considerations
Before replacing 539108366:
- Park the equipment on a stable, level surface.
- Shut off the engine.
- Remove the ignition key where applicable.
- Allow all moving components to stop.
- Disconnect the spark plug or battery where appropriate.
- Secure the equipment against unintended movement.
- Locate the fastener using the applicable parts diagram.
- Note the original washer, spacer, and nut arrangement.
- Remove the original fastener.
- Inspect the mounting holes and mating components.
- Verify that the replacement is 539108366.
- Position the components correctly.
- Insert the replacement bolt in the specified orientation.
- Reinstall applicable washers, spacers, and nuts.
- Tighten the fastener according to the equipment's service specifications.
- Verify that the secured components are correctly positioned.
- Check for proper clearance from nearby moving components.
Installation Tips
During installation:
- Confirm the correct 1/2-13 thread specification
- Verify the required 4-inch length
- Use the correct mating nut
- Start threads by hand where practical
- Avoid cross-threading
- Use properly fitting tools
- Reinstall washers and spacers in their original locations
- Follow model-specific tightening specifications
- Do not substitute lower-grade hardware
- Do not shorten or modify the bolt to force compatibility
- Verify clearance after installation
Important Notes
- Verify compatibility with your exact equipment model, product number, serial number, and assembly before ordering.
- Match part number 539108366 directly with the applicable OEM parts documentation.
- 539108366 is specified as HCS 1/2-13 x 4 GR 5.
- The fastener has a nominal 1/2-inch diameter.
- Thread specification is 1/2-13.
- Thread count is 13 threads per inch.
- Nominal length is 4 inches.
- Strength classification is Grade 5.
- This is a hex cap screw / hex-head fastener.
- The exact installation location is equipment-model dependent.
- Do not assume every 1/2-13 x 4-inch bolt is an appropriate replacement.
- Fastener grade, thread specification, length, construction, and application must match.
- Do not substitute a lower-strength fastener.
- Do not substitute a different thread pitch.
- Use 539108366 as the primary fitment reference.
- Inspect mating threads before installation.
- Replace damaged nuts, washers, or mounting hardware as necessary.
- Do not force the fastener into damaged or mismatched threads.
- Do not cut, weld, grind, drill, bend, or otherwise modify the replacement bolt.
- Follow the applicable equipment torque specifications when available.
- Verify that the fastener does not interfere with moving components after installation.
- Shut off the engine and prevent accidental starting before servicing equipment hardware.
- Securely support the equipment if access requires raising it.
- This listing is for one Husqvarna 539108366 1/2-13 x 4-Inch Grade 5 Hex Cap Screw only unless otherwise specified. Nuts, washers, spacers, brackets, and other mounting components are sold separately unless explicitly included.
- Match Husqvarna 539108366 with your equipment's OEM parts documentation before ordering to ensure proper fitment.
