Round Nut

Round Nut — Product Introduction

A round nut is a circular fastener commonly used for the axial positioning and locking of shaft-type parts, usually used in conjunction with a lock washer. Its outer cylindrical surface features four (or six) axial slots or radial holes for installation and removal with a hook spanner or dedicated wrench. Round nuts mostly adopt fine-pitch threads, offering good self-locking, high positioning accuracy, and large axial load capacity, and are widely used on various mechanical drive shafts, spindles, and locations requiring reliable axial fixation. Common materials include carbon steel, alloy steel, and stainless steel, and the surface can be treated by blackening, zinc plating, nickel plating, or phosphating to meet rust-prevention and wear-resistance requirements in different environments.

I. Product Features

• Round structure, easy installation: The nut has a circular shape with a relatively small outer diameter and a compact structure, suitable for shaft ends or positions with limited internal space. Slots or holes are cut on the side so that dedicated tools such as a hook spanner or round-nut wrench can be used for assembly and disassembly.
• Fine-pitch thread with good self-locking: Round nuts generally adopt fine-pitch threads; with a small pitch and small lead angle, their inherent anti-vibration and anti-loosening capability is superior to ordinary coarse-pitch threads, and they can withstand large axial locking forces.
• Usually used with a lock washer: During installation the round nut presses the lock washer, and the washer’s inner tongue is engaged into the shaft groove while the outer tongue is bent into the slot of the round nut, forming a reliable mechanical anti-loosening structure that prevents the nut from loosening under vibration.
• High positioning accuracy: Through control of the thread engagement length and end-face pressing force, accurate axial positioning and clearance adjustment of parts such as bearing inner rings, gears, and sprockets can be achieved, suitable for locations with high assembly-precision requirements.
• Complete range of sizes: The thread size range is wide; common metric fine-pitch threads are available in standard series from small to relatively large diameters, meeting different shaft diameters and load requirements.
• Diverse materials and surface treatments: Depending on service conditions, materials such as carbon steel, alloy steel, or stainless steel can be selected, and surface treatments such as blackening, zinc plating, nickel plating, and phosphating improve corrosion resistance and appearance quality.

II. Product Advantages

• Reliable anti-loosening: When used with a lock washer, multiple anti-loosening measures are formed, effectively preventing nut back-off caused by vibration or impact and ensuring long-term stability of axial positioning.
• Large axial load capacity: The fine-pitch thread provides a large contact area, and the round nut’s end face, together with the lock washer, bearing, or shaft shoulder, forms a planar press fit capable of withstanding large axial preload and working loads.
• Compact structure, space-saving: Compared with ordinary hex nuts, round nuts have a smaller outer diameter and relatively thinner thickness, better suited for installation in compact spaces such as shaft ends and bearing interiors.
• Easy assembly/disassembly, reusable: Using a dedicated hook spanner or round-nut wrench, the nut can be quickly tightened or loosened; the operation is simple, and the nut and shaft threads are not easily damaged during disassembly, allowing repeated use.
• Flexible adjustment: Through insertion depth and tightening torque, bearing clearance, gear meshing position, and axial gap can be conveniently adjusted, meeting precision assembly and maintenance needs.
• Wide applicability: Can be used both in general mechanical equipment and in medium-to-high load applications such as machine tools, automobiles, construction machinery, wind power, and mining equipment, with strong versatility.

III. Application Scope

• Machine tools and precision equipment: Axial positioning and locking of spindles, drive shafts, lead screws, and bearing housings, used to adjust bearing preload and axial clearance.
• Gearboxes and transmission devices: Bearing clamping and axial fixation of gear shafts, worm shafts, and input/output shafts, preventing shaft-system movement.
• Automotive and motorcycle parts: Locking and positioning at half shafts, drive shafts, steering knuckles, hub bearings, gearbox shaft ends, and other locations.
• Construction machinery and agricultural machinery: Axial fixation of hydraulic motor shafts, drive axles, running wheels, pulleys, sprockets, and other components.
• Wind power and new-energy equipment: Locking and axial positioning of shaft-system parts in wind turbine main shafts, yaw systems, pitch systems, and gearboxes.
• Mining and metallurgical equipment: Fastening and positioning of heavy machinery shaft ends such as crushers, conveyors, rolling mills, and mixing equipment.
• Bearing installation and maintenance: Axial clamping and clearance adjustment of bearing inner rings, ensuring bearing running accuracy and service life.
• General machinery and automation equipment: Locking and adjustment of shaft-type parts such as motor shafts, pump shafts, fan shafts, packaging machinery, printing machinery, and textile machinery.