DIN 5903 Fish Bolt | Oval Neck Marine Track Bolt
DIN 5903 Fish Bolt | Oval Neck Marine Track Bolt
DIN 5903 | M12–M27 | Grade 4.6 / 4.8 / 8.8 | Carbon Steel Black Oxide / Hot-Dip Galvanized
DIN 5903 fish bolt with dome head and oval neck anti-rotation design for ship deck crane rail, hatch cover track, and winch guide mounting. Through-bolting solution with cotter pin nut for vibration-prone marine applications.
Product Overview
TheDIN 5903 Fish Bolt is a specialized track bolt featuring a dome-shaped (mushroom) head and an elliptical oval neck section that prevents rotation during installation and service. The oval neck seats precisely into slotted holes of rail baseplates or channel flanges, creating a self-locking anti-rotation fit that eliminates the need for wrench access on the bolt head side.
This design makes DIN 5903 fish bolts ideal for marine deck applications where crane travel rails, hatch cover guide tracks, and winch base sliding guides require secure, maintenance-friendly fastening. The bolt is secured with a standard nut on the protruding thread end, typically locked with a cotter pin or prevailing torque nut to resist loosening under vibration and dynamic loading.
Key Features & Benefits
- Anti-Rotation Oval Neck: Elliptical profile seats into slotted rail holes, preventing bolt rotation during tightening and service
- Dome Head Design: Smooth rounded head provides low-profile appearance and reduces snag hazard on deck equipment
- Through-Bolting Solution: Requires access to only one side (nut side) for installation, simplifying assembly in confined spaces
- Cotter Pin Compatibility: Thread end drilled for cotter pin, providing positive lock against nut loosening under vibration
- Maintainability: Removable and reusable for periodic rail inspection and replacement, unlike embedded anchor systems
Technical Specifications
| Parameter | Value |
|---|---|
| Standard | DIN 5903 (Fish Bolt with Oval Neck) |
| Size Range | M12 – M27 |
| Length Range | 60 mm – 300 mm (standard); custom lengths on request |
| Head Shape | Dome Head / Mushroom Head / Round Head |
| Neck Profile | Oval Neck (Anti-Rotation); Square Neck available on request |
| Material Grade | Grade 4.6 / 4.8 (Low-Medium Carbon Steel); Grade 8.8 (Medium Carbon Steel, Quenched & Tempered) |
| Tensile Strength | Grade 4.6: 400 MPa; Grade 4.8: 420 MPa; Grade 8.8: 800 MPa |
| Yield Strength | Grade 4.6: 240 MPa; Grade 4.8: 340 MPa; Grade 8.8: 640 MPa |
| Surface Finish | Black Oxide / Hot-Dip Galvanized (≥50 μm) / Zinc Plated |
| Thread | Metric Coarse (ISO 261); Cotter pin hole drilled on thread end |
| Oval Neck Tolerance | ±0.2 mm for precise fitment in rail base slots |
Dimensional Data (Selected Sizes)
| Thread | d (mm) | D (mm) | Oval Neck (mm) | L Range (mm) | Thread Length (mm) |
|---|---|---|---|---|---|
| M12 | 12 | 24 | 14 × 12 | 60–150 | 30–40 |
| M16 | 16 | 30 | 18 × 15 | 80–200 | 40–50 |
| M20 | 20 | 36 | 22 × 18 | 100–250 | 50–60 |
| M24 | 24 | 44 | 26 × 22 | 120–300 | 60–70 |
| M27 | 27 | 50 | 30 × 24 | 140–300 | 70–80 |
Note: d = thread diameter; D = dome head diameter; Oval Neck = width × height of elliptical section. Dimensions are representative per DIN 5903. Contact us for complete dimensional tables and custom oval neck sizes.
Marine Applications
- Deck Crane Rails: Through-bolting for crane travel rail baseplates on container cranes, gantry cranes, and telescopic boom cranes
- Hatch Cover Tracks: Guide track fastening for rolling-type and lifting-type hatch covers subject to wave-induced deck flexure
- Winch Base Guides: Sliding guide channel mounting for mooring winches, capstans, and anchor windlasses
- Stowage Rack Mounting: Removable rack segment fastening for container cell guides and cargo securing rails
- Deck Machinery Rails: Equipment positioning rails requiring periodic adjustment and maintenance access
Material Grade Selection Guide
| Application | Recommended Grade | Surface Treatment |
|---|---|---|
| General deck equipment (low load) | Grade 4.6 / 4.8 | Black Oxide or Hot-Dip Galvanized |
| Crane travel rail (high load) | Grade 8.8 | Hot-Dip Galvanized (≥50 μm) |
| Hatch cover track (moderate load) | Grade 4.8 / 8.8 | Hot-Dip Galvanized |
| Indoor / Dry compartment | Grade 4.6 | Zinc Plated or Plain |
Installation Guidelines
- Ensure rail baseplate slotted hole matches the oval neck dimensions (width and height) for proper anti-rotation fit.
- Insert the fish bolt through the rail base and underlying structural member from the top side.
- Place a hardened flat washer under the nut to distribute load and prevent damage to the rail base surface.
- Tighten the nut to the specified torque. The oval neck will prevent the bolt head from rotating.
- For vibration-prone applications, secure the nut with a cotter pin through the drilled hole or use a prevailing torque nut.
- Inspect oval neck fitment after initial torqueing — if the bolt rotates during nut tightening, the oval neck is undersized and must be replaced.
- Re-torque after 24–48 hours of service to account for initial embedding and relaxation.
Why Choose SINOFASTENER
- Manufactured per DIN 5903 with oval neck tolerance ±0.2 mm for precise rail slot fitment
- Full size range M12–M27 with lengths up to 300 mm, Grade 4.6/4.8/8.8 available from stock
- Hot-dip galvanized coatings tested per ISO 1461 for minimum 50 μm thickness
- Cotter pin holes accurately drilled and deburred for easy pin insertion
- Annual production capacity 50,000 tons across all fastener categories
- Material certificates and dimensional inspection reports provided with every shipment
FAQ
What is the purpose of the oval neck on a DIN 5903 fish bolt?
The oval neck provides anti-rotation functionality. When the elliptical neck section seats into a matching slotted hole in the rail baseplate, it prevents the bolt from rotating during nut tightening and service. This eliminates the need for wrench access on the bolt head side, which is critical in confined deck equipment assemblies.
Can DIN 5903 fish bolts be used with square neck instead of oval neck?
Yes, square neck variants are available on request. Square neck fish bolts provide stronger anti-rotation resistance but require larger square holes in the rail baseplate. Oval neck is preferred for standard applications due to easier hole preparation and smoother load distribution.
What grade should I select for crane rail applications?
Grade 8.8 is recommended for crane travel rail applications due to higher tensile strength (800 MPa) and yield strength (640 MPa). Grade 4.6/4.8 is suitable for lighter-duty deck equipment where loads are moderate. Always consult the crane manufacturer's bolting specifications for exact grade requirements.
How do I prevent the nut from loosening under vibration?
Use a cotter pin through the drilled hole in the bolt thread end, combined with a slotted nut or castle nut. Alternatively, use a prevailing torque nut (e.g., all-metal lock nut) for applications where cotter pin access is limited. Re-torque after initial service period to account for embedding.
What surface finish is best for marine environments?
Hot-dip galvanized (minimum 50 μm coating thickness per ISO 1461) is recommended for deck-level applications exposed to seawater spray. For indoor or dry compartment use, zinc plating or black oxide provides adequate protection at lower cost. For highly corrosive environments, consider stainless steel fasteners instead.
Contact Us
For DIN 5903 fish bolt inquiries, please contact:
E-mail:sales@sinofastener.com
SINOFASTENER — Marine Fastener Supplier | Annual Capacity 50,000 Tons
