Shoulder Bolts: Complete Guide
Precision Shoulder Screws for Pivot Points, Bearing Surfaces & Sliding Mechanisms
Types & Configurations
Standard, metric, and stripper bolt options
Specifications
Precision tolerances and dimensions
Size Charts
Complete sizing for inch and metric
Applications
Pivots, bearings, and precision assemblies
Downloadable Reference Guides
Quick access to all shoulder bolt specification charts and guides
What Are Shoulder Bolts?
Shoulder bolts (also called shoulder screws or stripper bolts) are precision fasteners featuring a smooth, cylindrical shoulder section between the head and threaded portion. The shoulder acts as a precision shaft or bearing surface while the threaded end secures the assembly. This unique design makes shoulder bolts ideal for pivot points, sliding mechanisms, and applications requiring a precision-ground rotating or sliding surface.
Unlike standard bolts where the entire shank is threaded, shoulder bolts have a distinct unthreaded shoulder with tight diameter tolerances (typically ±0.001" or better). This precision shoulder maintains consistent clearances in bearing applications and provides a smooth surface for rotating or sliding components.
Key Advantages of Shoulder Bolts
Precision bearing surface: Ground shoulder maintains tight tolerances for consistent clearances and smooth operation.
Dual function: Acts as both a fastener and a precision shaft, eliminating need for separate axle or pin.
Controlled clearance: Shoulder diameter tolerance allows specific fits (sliding, running, or close clearance).
Load distribution: Shoulder spreads bearing loads over larger area than threaded shank would.
Replaceable bearing: Worn bushings can be replaced while reusing the precision shoulder bolt.
Shoulder Bolt Types and Configurations
Standard Shoulder Bolts (Inch)
Most common type with socket head cap screw head, precision-ground shoulder, and coarse thread UNC threads.
- Socket head (hex socket drive)
- Precision ground shoulder (±0.001")
- UNC coarse threads
- Alloy steel, heat treated
- Black oxide finish standard
Metric Shoulder Screws
Metric dimensions with DIN/ISO specifications, precision shoulder, and metric coarse pitch threads.
- Metric shoulder diameters
- Metric coarse pitch threads
- DIN 7379 specification
- Precision ground surface
- International standard
Stripper Bolts
Specific type of shoulder bolt designed for die and mold work, often with longer shoulders and special head configurations.
- Extra-long shoulder lengths
- Precision ground to tight tolerances
- Die and mold applications
- Socket head or button head
- Various shoulder length options
Stainless Steel Shoulder Bolts
Corrosion-resistant option for outdoor, marine, or food processing applications requiring precision shoulders.
- 304 or 316 stainless steel
- Corrosion resistance
- Ground shoulder precision
- Food-safe, non-magnetic
- Lower strength than alloy steel
Low-Profile Shoulder Bolts
Button head or low-profile socket head for applications where standard head height creates clearance issues.
- Reduced head height
- Button head design
- Limited clearance applications
- Same precision shoulder
- Lower drive torque capacity
Custom Shoulder Bolts
Special sizes, materials, or configurations for unique application requirements not met by standard catalog items.
- Non-standard shoulder diameters
- Special shoulder lengths
- Custom materials or finishes
- Tight tolerance requirements
- Minimum order quantities apply
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Call (866) 573-0445 Browse All Shoulder BoltsShoulder Bolt Specifications and Dimensions
Understanding shoulder bolt dimensions is critical for proper application. Four key measurements define a shoulder bolt:
Critical Dimensions
- Shoulder Diameter (D): The precision-ground cylindrical section diameter, typically held to ±0.001" or tighter
- Thread Size (T): The threaded portion diameter (always smaller than shoulder diameter)
- Shoulder Length (L): Length of the unthreaded shoulder section from under the head to start of threads
- Thread Length (TL): Length of the threaded portion, typically 0.5" to 1.0" depending on size
- Overall Length (OAL): Total length from under head to end of threads (Shoulder Length + Thread Length)
Tolerance Standards
Shoulder Diameter Tolerance: Standard precision shoulder bolts maintain ±0.001" (0.0254mm) tolerance on shoulder diameter. This allows for close-fitting applications with bushings or bearings.
Shoulder Length Tolerance: Typically ±0.015" (0.4mm) on shoulder length. Critical applications may require tighter tolerances.
Thread Fit: Class 2A thread fit standard for easy assembly with Class 2B tapped holes.
Surface Finish: Ground shoulder surface typically 32 microinch or better for smooth bearing operation.
Sizing Nomenclature
Shoulder bolts are specified using this format: Shoulder Diameter × Shoulder Length, Thread Size
Example: 1/2" × 2", 3/8"-16 means:
- Shoulder diameter: 1/2" (0.500")
- Shoulder length: 2.000"
- Thread size: 3/8"-16 UNC
Shoulder Bolt Size Charts
Standard Inch Sizes
| Shoulder Diameter | Thread Size | Hex Socket Size | Head Diameter | Common Shoulder Lengths | Typical Thread Length |
|---|---|---|---|---|---|
| 1/4" (0.250") | #10-32 | 3/32" | 3/8" | 1/4" - 3" | 0.50" |
| 5/16" (0.3125") | 1/4"-20 | 1/8" | 15/32" | 1/4" - 4" | 0.62" |
| 3/8" (0.375") | 1/4"-20 | 5/32" | 9/16" | 1/2" - 4" | 0.62" |
| 1/2" (0.500") | 3/8"-16 | 3/16" | 3/4" | 1/2" - 6" | 0.75" |
| 5/8" (0.625") | 3/8"-16 | 1/4" | 15/16" | 3/4" - 6" | 0.75" |
| 3/4" (0.750") | 1/2"-13 | 5/16" | 1-1/8" | 1" - 8" | 1.00" |
| 1" (1.000") | 5/8"-11 | 3/8" | 1-1/2" | 1" - 10" | 1.25" |
Note: Shoulder lengths shown are common stock sizes. Many manufacturers offer 1/4" or 1/2" increments. Thread lengths are typical and may vary by manufacturer.
Metric Shoulder Screws (DIN 7379)
| Shoulder Dia (mm) | Thread Size | Hex Socket (mm) | Head Dia (mm) | Common Shoulder Lengths | Thread Length |
|---|---|---|---|---|---|
| 6 | M4 | 3 | 10 | 10-80mm | 16mm |
| 8 | M5 | 4 | 13 | 10-100mm | 20mm |
| 10 | M6 | 5 | 16 | 12-120mm | 22mm |
| 12 | M8 | 6 | 18 | 16-140mm | 26mm |
| 16 | M10 | 8 | 24 | 20-160mm | 32mm |
| 20 | M12 | 10 | 30 | 25-200mm | 38mm |
Download Shoulder Bolt Size Chart
Complete sizing for inch and metric with dimensions and tolerances.
Download Size Chart (PDF)Selecting Shoulder Length
Minimum shoulder length: Must extend through the entire thickness of components that slide or rotate on the shoulder, plus clearance.
Thread engagement: Ensure adequate thread depth in tapped hole (minimum 1× thread diameter for steel, 1.5× for aluminum).
Clearance: Allow 0.030"-0.060" clearance between end of shoulder and bottom of component to prevent binding.
Example calculation: For 0.750" thick component requiring sliding fit: Shoulder length ≥ 0.750" + 0.050" clearance = 0.800" minimum (use next available standard length)
Need Specific Sizes or Custom Configurations?
We stock standard sizes with fast delivery and can source custom shoulder bolts for special requirements.
Shop Standard Sizes Call for Custom QuoteCommon Applications
Pivot Points and Hinges
Creating smooth pivoting action in mechanical linkages, doors, and articulated mechanisms.
- Machine linkages and mechanisms
- Robotic joints and actuators
- Hinged assemblies
- Articulated arms
- Requires close clearance fit
Bearing Surfaces
Shoulder acts as precision shaft for bushings or bearings in rotating or oscillating assemblies.
- Bushing mounting applications
- Needle bearing supports
- Rotating wheel or roller mounts
- Low-friction bearing surfaces
- Replaceable bushing systems
Sliding Mechanisms
Precision shoulder provides smooth guide surface for linear sliding components and adjustable assemblies.
- Linear slides and guides
- Adjustable brackets
- Drawer slides
- Telescoping mechanisms
- Precision positioning systems
Die and Mold Work
Stripper bolts in stamping dies, injection molds, and progressive die assemblies.
- Stripper plates in stamping dies
- Mold plate assembly
- Progressive die construction
- Precision alignment
- Long shoulder lengths available
Jigs and Fixtures
Creating precise reference points and rotation axes in manufacturing fixtures and tooling.
- Welding fixtures
- Assembly jigs
- Inspection fixtures
- Rotary indexing
- Precision alignment pins
Cams and Followers
Mounting cam followers and creating smooth cam surfaces in automated machinery.
- Cam follower mounting
- Timing mechanisms
- Automated machinery cams
- Conveyor systems
- Packaging equipment
Download Application Guide
Common uses, clearance calculations, and bushing selection for shoulder bolt applications.
Download Application Guide (PDF)Material and Finish Options
Alloy Steel (Standard)
Heat-treated alloy steel provides high strength for most applications:
- Material: SAE 12L14 or similar alloy steel
- Heat treatment: Through-hardened or case-hardened
- Hardness: Rc 45-53 typical for wear resistance
- Black oxide finish: Basic corrosion protection, most economical
- Zinc plated: Better corrosion resistance for indoor use
Stainless Steel
Corrosion-resistant option with precision-ground shoulders:
- 304 Stainless (18-8): Good corrosion resistance, most applications
- 316 Stainless: Superior corrosion resistance, marine/chemical environments
- Strength consideration: Lower tensile strength than alloy steel
- Passivated finish: Enhanced corrosion resistance
- Non-magnetic: Suitable for magnetic-sensitive applications
Special Coatings
- Zinc-nickel plating: Superior corrosion protection, automotive applications
- Electroless nickel: Uniform coating thickness, excellent wear resistance
- Phosphate coating: Improved lubricity, corrosion protection
- Black zinc: Corrosion resistance with darker appearance
Installation and Assembly Guidelines
Proper Installation Procedure
- Select correct clearance: Choose shoulder bolt diameter based on bushing or bearing ID and desired fit
- Verify shoulder length: Ensure shoulder extends through component thickness with proper clearance
- Prepare tapped hole: Thread depth must accommodate thread length plus 2-3 threads minimum clearance
- Install bushing (if used): Press-fit bushing into component before installing shoulder bolt
- Align components: Position all parts on shoulder bolt before threading into base
- Thread shoulder bolt: Start threads by hand to avoid cross-threading
- Tighten to specification: Use torque appropriate for thread size, do not over-tighten
- Check clearances: Verify smooth operation and proper clearances before final assembly
Bushing Selection and Fit
Bushings provide the bearing surface and are typically press-fit into the component:
- Bronze bushings: Good for low-speed, moderate-load applications
- Oilite (sintered bronze): Self-lubricating for maintenance-free operation
- Plastic bushings (PTFE, acetal): Low friction, corrosion resistant, quieter operation
- Needle bearings: High load capacity in compact envelope
- Clearance fit: 0.001"-0.003" clearance between shoulder and bushing ID for smooth rotation
Download Bushing Selection Chart
Bushing types, materials, and fit tolerances for shoulder bolt applications.
Download Bushing Selection Chart (PDF)⚠️ Installation Best Practices
Do not over-tighten: Excessive torque can deform shoulder or strip threads. Use torque specs for thread size.
Check shoulder protrusion: Shoulder end should not bottom out in bushing - maintain 0.030"-0.060" clearance.
Lubrication: Apply appropriate lubricant to shoulder surface and bushing for break-in and ongoing operation.
Thread engagement: Minimum 1× thread diameter into steel, 1.5× into aluminum for full strength.
Inspect shoulder surface: Nicks, burrs, or damage to ground shoulder will cause premature bushing wear.
Download Installation Guide
Step-by-step installation procedures and best practices for shoulder bolt assemblies.
Download Installation Guide (PDF)Ready to Order Shoulder Bolts?
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