STAINLESS STEEL HEXAGON CASTLE NUTS DIN 935

Hexagon Castle Nuts DIN 935 — A castle nut gets its name from the slots machined into the crown, which look like a castle's battlements, and those slots exist for one purpose: once the nut is tightened to the correct position, a split pin is passed through a transverse hole in the bolt or shaft and through the aligned slots, physically locking the nut against rotation regardless of vibration, shock, or any loss of thread friction over time. That's a fundamentally different, and more certain, locking method than friction-based options like a nylon insert or serrated flange nut — a split pin can't work loose the way thread friction can degrade, which is exactly why castle nuts are specified in safety-critical rotating and axle applications: automotive wheel bearing retention, steering linkages, suspension components, and similar joints where a nut backing off in service could cause a serious failure rather than just an inconvenience. The split pin is what makes the lock work, not the nut alone — fitted without a pin, a castle nut behaves like a standard hexagon nut relying purely on friction and torque, so for safety-critical use the split pin should always be fitted, never treated as optional or added "if there's time." DIN 935 is the full-height version, giving greater thread engagement than the thin-type DIN 937 castellated nut, and is the better choice wherever load capacity matters as much as the mechanical lock; DIN 937 trades some of that engagement for a lower stack height where axial space is limited. Positioning matters at assembly: the nut must be tightened to a position where the slots actually align with the shaft's cross-hole, which sometimes means backing off slightly from maximum torque to reach alignment — a torque range rather than a single figure is typically specified for this reason. A2 stainless suits general machinery use; A4 is worth the extra cost for automotive, marine, or outdoor axle applications exposed to road salt or weather. Sizing follows the mating bolt and shaft exactly.

FAQs
What happens if the slots don't quite align at the specified torque?
This is a known characteristic of castellated nuts rather than a fault — a small torque range is typically specified precisely so the nut can be tightened to the nearest position where the slots align with the shaft's cross-hole, rather than forcing an exact single torque figure.

Can a castle nut be reused after the split pin is removed?
The nut itself can often be reused, but a new split pin should always be fitted rather than reusing a bent one, since a split pin that's already been opened and straightened once is weaker and more prone to failure the second time.

How does DIN 935 differ from DIN 937?
DIN 935 is a full-height castellated nut, providing greater thread engagement, while DIN 937 is a thin-type castellated nut with the same slotted crown principle but a lower body height, used where axial space is more limited.

Is a split pin required every time, or can the nut be used without one?
The split pin is the mechanism that provides the positive lock; without it, the nut behaves like a standard hexagon nut relying only on friction and torque. For safety-critical use, the split pin should always be fitted.