Slotted Nut

Slotted Nut — Castle / Slotted Hex Nut | DIN 935 / DIN 936 | Cotter Pin Safety Locking

Slotted nuts, also known as castle nuts, feature slots in the top surface that allow insertion of a cotter pin or split pin through a drilled hole in the bolt, creating a positive mechanical lock that prevents loosening under the most extreme vibration and shock conditions. Manufactured to DIN 935 (castle nut with crown) and DIN 936 (slotted hex nut) standards, our slotted nuts are available in M4 to M48 sizes in carbon steel and stainless steel. Widely used in safety-critical applications where fastener failure could result in catastrophic consequences — automotive steering, aerospace, railway, lifting equipment, and military hardware.

Material & Specifications

Size Range	M4 to M48 / 5/16″ to 2″
Standard	DIN 935 (castle nut), DIN 936 (slotted hex), ANSI B18.2.2, NASM25027, ISO 7035
Material	Carbon Steel (Grade 5, 8, 10), 304 Stainless Steel (A2), 316 Stainless Steel (A4), Alloy Steel (4140/4340)
Surface / Coating	Electroplated Zinc (Blue/White, Yellow/Color), Dacromet, Multi-Element Alloy Co-Permeation, Hot-Dip Galvanized, Phosphated + Oiled
Slot Type	DIN 935 (tall castle with crown) or DIN 936 (standard height slotted)
Slots	4-slot or 6-slot configurations available

Surface Treatment & Zinc Coating Quality

Slotted nuts are used in safety-critical applications where long-term corrosion resistance is essential to maintain mechanical integrity. Our premium coating options:

• Hot-Dip Galvanizing (HDG) — Thick zinc layer (50-120μm) providing superior corrosion protection for outdoor structural and marine slotted nut applications. Compliant with ISO 1461 / ASTM A153. Salt spray resistance: 500-1,000+ hours. Centrifuge-spun for uniform coating in slot openings.
• Electroplated Zinc Blue-White (Zn Blue/White) — Bright silver-blue finish with 5-12μm zinc layer. Cr3+ trivalent passivation, RoHS compliant. Suitable for general-purpose slotted nut applications. Baked post-plating to prevent hydrogen embrittlement in high-strength grades.
• Color Zinc / Yellow Zinc (Iridescent Passivation) — Golden-iridescent multi-colored passivation providing 150-250 hours salt spray resistance. Preferred for automotive and aerospace slotted nuts requiring visual coating identification and enhanced corrosion protection.
• Dacromet Coating — The preferred coating for safety-critical slotted nuts. Water-based zinc-chromium flake coating with NO hydrogen embrittlement risk. 1,000-1,500 hours salt spray resistance. Thin, uniform coating that does not interfere with cotter pin slot engagement. Ideal for aerospace, military, and railway applications.
• Multi-Element Alloy Co-Permeation — Zinc-aluminum-magnesium-rare earth alloy layer providing 2,000+ hours salt spray resistance with self-healing properties. Used in critical infrastructure slotted nuts for cross-sea bridges, offshore platforms, and wind turbine blade connections.

Key Features

• Positive mechanical locking via cotter/split pin — the most reliable anti-loosening method available
• Available in both castle (DIN 935, tall with crown) and slotted hex (DIN 936, standard height) designs
• 4-slot and 6-slot configurations to accommodate various cotter pin angles
• Must be paired with drilled-shank bolts for cotter pin installation
• Mandatory in safety-critical: steering systems, lifting equipment, aircraft landing gear

Applications

• Automotive steering and suspension tie-rod ends
• Aerospace and aircraft structural connections
• Lifting equipment, cranes, and hoists
• Railway track and rolling stock safety connections
• Military and defense equipment fastening

Why Choose BoltNutsPlus?

• ISO 9001:2015 Certified Manufacturing — consistent quality you can trust
• 15+ Years of Export Experience — serving 40+ countries worldwide
• Full Traceability — material certificates (EN 10204 3.1) and test reports included
• Custom Packaging & OEM/ODM — your brand, your specifications
• Third-Party SGS / Bureau Veritas Inspection Available
• 24-Hour Quote Response — same-day reply for urgent requirements