Shoulder screws, also known as shoulder bolts or stripper bolts, are precision-engineered fasteners that provide accurate alignment, smooth rotational motion, and controlled spacing in mechanical assemblies. Designed with a three-part construction a drive head, precision-ground shoulder, and threaded section these screws serve multiple roles such as shafts, spacers, pivot points, and bearing surfaces. They are critical in applications demanding tight tolerances, repeatable accuracy, and dependable mechanical performance.
Unlike standard threaded fasteners, precision shoulder screws deliver both fastening strength and functional motion capabilities, making them an indispensable choice for machinery design, robotics, and automation systems. Their unthreaded shoulder section is manufactured to strict tolerances (typically +0.000/-0.001 inch) to ensure consistent fit and smooth operation. Common uses include mounting gears, bearings, linkages, and pulleys where precise spacing and alignment are essential. These fasteners reduce the need for custom-machined components, lowering manufacturing costs while simplifying assembly.
• Precision-ground shoulder provides an ideal bearing surface for rotating components and linear guides.
• Hex socket drive ensures maximum torque transfer in tight spaces with reduced risk of head stripping.
• Tight manufacturing tolerances guarantee accurate positioning and repeatable alignment in precision equipment.
• Available in corrosion-resistant stainless steel, heat-treated alloy steel, brass, titanium, and aluminum.
• Multi-functional design allows use as a shaft, spacer, pivot, or guide a versatile solution in compact assemblies.
• Optional thread-locking mechanisms (nylon inserts, pre-applied patches, or crimped threads) enhance reliability under vibration.
• Compatible with standard ball and needle bearings, bronze bushings, and thrust washers.
• Widely used in aerospace, automotive, robotic, and injection molding systems requiring precision motion control.
• Head Style: Hex socket (standard), slotted, Phillips, and external hex head configurations
• Materials: 303 stainless steel (Rockwell B83), 416 stainless steel (heat-treated C26–32), alloy steel, brass, aluminum 2024-T4, titanium Grade 5
• Shoulder Diameter Tolerance: +0.000/-0.001 inch (tighter ranges on request)
• Size Range: Shoulders from 3/32" to 1-1/2" diameter; threads from #2-56 to 5/8"-11 (metric M3–M20)
• Shoulder Length: 3/32" to 6" in standard increments; custom options available
• Thread Length: 1.5–2 times thread diameter; custom lengths upon request
• Standards: NASM51576 (hex socket), NASM51575 (slotted), DIN 7379, ISO 7379, MS51957
• Head Profiles: Standard, low-profile, ultra-low, and extended head variations
• Surface Finish: Ground and polished shoulder, Ra 32 microinches or better