DIN 935 Slotted Nut | Hexagon Castle Nut Marine

DIN 935 hexagon slotted nut (also called castle nut) for marine slotted nut engine room applications where mechanical locking with cotter pin is required. Manufactured in carbon steel with HDG, Dacromet, zinc flake, and A4-70 (316) stainless steel. M6–M48 metric coarse thread, supplied with matching cotter pins per ISO 1234 / DIN 94. Replaces outdated DIN 935 slotted nut inventory with full ISO 7035 / 7036 traceability.

What Is a Hexagon Slotted Nut and Castle Nut?

Ahexagon slotted nut is a standard hexagonal nut with six radial slots cut into the top portion of the nut body. The slots align with a pre-drilled hole in the bolt shank or threaded rod, allowing a cotter pin (split pin) to pass through the nut and bolt — creating a positive mechanical lock that cannot vibrate loose under any condition.

Castle nut is the American English term for the same product — the six slots resemble the crenellations of a castle wall, giving it its common name. In marine slotted nut service, the castle nut design is preferred over nylon-insert lock nuts in high-temperature environments (above 120 deg C) where nylon degrades, and over serrated flange nuts where a fail-safe mechanical lock is required for safety-critical joints.

Theslotted nut cotter pin assembly is the standard mechanical locking method specified in ship classification society rules for steering gear linkages, rudder stock connections, propeller shaft retaining nuts, and deck crane slewing ring bolts. Unlike friction-based locking methods, the slotted nut cotter pin system provides a visible, verifiable positive lock that can be inspected without disassembly.

Marine Applications

Note: The following applications are based on typical industry practice for DIN 935 / ISO 7035 hexagon slotted nuts in marine and offshore environments.

Specifications & Materials

Why Choose sinofastener for Marine Slotted Nuts?

Standards Reference

• DIN 935 — Hexagon slotted nuts (superseded by ISO 7035 / 7036, still widely specified)
• ISO 7035 — Hexagon slotted nuts, product grades A and B
• ISO 7036 — Hexagon slotted nuts, product grade C
• ISO 1234 — Split cotter pins (matching pin for slotted nut locking)
• DIN 94 — Split pins (German national standard equivalent to ISO 1234)
• ISO 898-2 — Mechanical properties of nuts (carbon steel)
• ISO 3506-2 — Mechanical properties of stainless steel nuts
• ANSI/ASME B18.2.4.6M — Slotted Nuts, Metric Series (US equivalent)

FAQ

What is the difference between a hexagon slotted nut and a castle nut?

There is no functional difference — hexagon slotted nutandcastle nut are two names for the same product. DIN 935 / ISO 7035 use the term"slotted nut"in the standard text, while ASME/ANSI and US industry commonly use"castle nut"because the six top slots resemble castle crenellations. Both refer to a hexagonal nut with radial slots for cotter pin locking.

Why choose slotted nut cotter pin over nylon lock nut?

Theslotted nut cotter pin system provides a positive mechanical lock that does not degrade with temperature, chemical exposure, or time. Nylon-insert lock nuts lose their prevailing torque above 120 deg C and can become loose in sustained vibration. For safety-critical marine slotted nut applications — rudder stock, propeller shaft, steering gear — classification society rules typically require the slotted nut cotter pin positive locking method.

What bolt is required to use a DIN 935 slotted nut?

The bolt must have a pre-drilled transverse hole through the shank, positioned so that when the nut is tightened to the specified torque, at least one slot aligns with the bolt hole for cotter pin insertion. Per DIN 935, the bolt hole diameter and position are specified relative to the thread nominal diameter. We supply matched bolt-and-nut assemblies with pre-drilled holes on request.

Can you supply stainless steel cotter pins with A4-70 slotted nuts?

Yes. When ordering A4-70 (316 stainless) hexagon slotted nuts, we recommend matching AISI 316 cotter pins per ISO 1234 to maintain consistent corrosion resistance in seawater environments. Carbon steel cotter pins paired with stainless nuts will corrode first and compromise the locking function. We supply matched material kits as standard.