Visual Proof of a Secure Connection
Our castle nuts use a slotted crown that accepts a cotter pin after torqueing, creating a positive mechanical lock you can actually see. They’re ideal for rotating or high-vibration assemblies where standard nuts can back off, think suspensions, steering linkages, agricultural equipment, heavy machinery, and fixtures that take a daily beating.
Choose from carbon steel for everyday strength, zinc-plated steel for basic corrosion protection, and stainless steel for wet or corrosive environments. We machine clean, concentric threads for smooth run-on and repeatable clamp load. Need something specific for your line? Ask about bulk packs and finish consistency across lots.
Need to round out the build? Pair our nuts with a drilled bolt and a washer for proper load distribution, and consider our matching hardware like a Cotter Pin, Low Castle Nut, or Slotted Round Nut to suit your space and strength requirements.
DIN 935 castle nuts feature precision slots on the crown so a cotter pin can pass through the nut and the bolt’s cross-hole, preventing rotation after torqueing. This design is the industry standard wherever a nut must be secured against loosening due to shock or vibration. Our DIN 935 range delivers consistent slot alignment, crisp thread engagement, and dependable performance you can trust in the field.
How Castle Nuts Work
After tightening to spec, simply align a crown slot with the drilled hole in the bolt or stud. Insert the cotter pin, bend the legs, and you’ve created a visible, mechanical lock that will not loosen under vibration. No adhesives, no guesswork, just secure, serviceable fastening.
Sizing & Standards
Available in common metric sizes to DIN 935, our castle nuts are made for drilled bolts/studs with matching thread class. Crown height and slot geometry are held tightly so alignment with the bolt’s cross-hole is fast and predictable on the line.
Installation Tips
Torque to spec first, don’t rely on the cotter pin to “pull” the joint tight. If a slot doesn’t align, advance (never back off) to the next slot to maintain clamp load. Insert a correctly sized cotter pin fully through the hole and bend the legs around the crown to lock it in place. For service intervals, replace the cotter pin on reassembly for best practice.
FAQs
What is a castle nut used for?
A castle nut is used to secure critical joints that see shock, vibration, or rotation, such as steering and suspension parts. Once tightened, it is locked with a cotter pin through the nut slots and the bolt’s cross-hole. This mechanical lock prevents the nut from backing off in service.
What is another name for a castle nut?
Castle nuts are also known as slotted nuts or castellated nuts. The “castle” nickname comes from the crown-like slots on the top of the nut. In metric standards, you’ll often see them referenced as DIN 935.
Is a castle nut a locking nut?
Yes, when used with a cotter pin, a castle nut is a true mechanical locking system. Unlike nylon-insert locknuts, it relies on a physical pin to stop rotation. That makes it highly reliable under heat, oils, or solvents where polymers may fail.
What is the difference between castle nuts and regular nuts?
Regular nuts rely solely on thread friction and clamp load to stay tight. Castle nuts add a slotted crown so you can insert a cotter pin through a drilled bolt, creating a positive lock. This makes castle nuts the preferred solution for safety-critical, high-vibration assemblies.
