Alloy Socket Set Screws

Alloy steel socket set screws are headless, fully-threaded fasteners through-hardened to RC 45–53 per ASME B18.3, providing a point hard enough to bite into and hold on standard steel shafts. Used to lock gears, pulleys, cams, collars, and hubs onto shafts without any protruding head — the installed set screw sits flush or below the hub surface for a clean, snag-free assembly. Eugene Fastener stocks alloy socket set screws in cup, flat, cone, oval, and dog point styles across a full inch size range from stock in Eugene, Oregon.

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Alloy Steel Socket Set Screws — Inch Series, ASME B18.3, Multiple Point Styles

Shop Alloy Socket Set Screws

Alloy steel socket set screws are the standard choice for locking power transmission components — gears, sprockets, pulleys, cams, and shaft collars — onto steel shafts. Through-hardened to RC 45–53 per ASME B18.3, the point is hard enough to penetrate and grip an unhardened steel shaft under torque. The internal hex socket allows installation and removal in confined bores where a wrench cannot reach. Because there is no head, the installed fastener is completely contained within the tapped hole — no protrusion, no snagging.

Point Style Selection Guide

Cup Point is the standard choice for most set screw applications. The hardened, concave rim bites into the shaft surface under axial load, providing strong resistance to both rotation and axial movement. Cup point set screws leave a small ring indentation on the shaft — acceptable in most applications and useful for consistent repositioning. This is the point style to specify when in doubt.

Flat Point distributes load over a flat area rather than a sharp rim, minimizing shaft marring. Use flat point set screws on hardened or precision-ground shafts, or in applications requiring frequent adjustment without progressive shaft damage. Holding power is lower than cup point.

Cone Point is designed to seat permanently in a matching drilled dimple in the shaft, creating the highest holding power of any standard point style. Use cone point set screws where the fastener will not be moved after initial installation. Not suitable for adjustment applications.

Oval Point has a rounded tip that bears against the shaft with minimal surface contact and minimal damage. A good choice for soft shafts, instrument components, and optical equipment where appearance of the shaft matters and light holding force is sufficient.

Dog Point (Extended Tip) features a precision cylindrical pilot that drops into a corresponding hole or slot in the shaft, providing positive mechanical engagement rather than friction. Used where the set screw must be removed and reinstalled repeatedly in exactly the same position.

Specifications

Standard: ASME B18.3
Material: Alloy steel, through-hardened
Hardness: RC 45–53
Drive: Internal hex socket (Allen key)
Finish: Plain or black oxide
Thread Range: #0-80 through 1-1/2"-6

Hex Key Sizes for Alloy Set Screws

Set screws use smaller hex keys than cap screws of the same thread size. Common inch pairings: #8-32 uses 3/32 inch; #10-32 uses 3/32 inch; 1/4-20 uses 1/8 inch; 5/16-18 uses 5/32 inch; 3/8-16 uses 3/16 inch; 1/2-13 uses 1/4 inch; 5/8-11 uses 5/16 inch. Using an undersized key risks rounding the socket — always verify.

Frequently Asked Questions

What point style should I use for a standard set screw application?
Cup point is the correct default for most shaft-locking applications. It provides the best combination of holding power and installability for standard steel shafts. Use flat point when shaft surface condition must be preserved, cone point when permanent locking in a drilled dimple is required, and dog point when precise, repeatable repositioning is needed.

Can alloy set screws be used on hardened shafts?
No. Alloy socket set screws (RC 45–53) are not hard enough to penetrate or grip a hardened shaft surface. The point will deflect or skip rather than bite in, resulting in inadequate holding force and potential damage to the set screw point. Use flat point set screws against hardened shafts to distribute load without requiring penetration.

What is the difference between a set screw and a grub screw?
They are the same fastener — "grub screw" is the common British English term, "set screw" is standard in American English. Both refer to a headless, fully-threaded fastener driven by an internal hex socket.

How tight should I torque a set screw?
Use the manufacturer's recommended torque value for the thread size and point style. Over-tightening can shear the screw or cause excessive shaft damage; under-tightening allows the assembly to shift under load. Common reference values: #10-32 cup point approximately 35 in-lb; 1/4-20 approximately 87 in-lb; 5/16-18 approximately 165 in-lb; 3/8-16 approximately 290 in-lb. Use a calibrated torque driver for precision applications.

Alloy socket set screws are commonly used alongside shaft keys and keystock in keyed shaft assemblies, and with dowel pins in jig and fixture builds where precise location must be maintained. For corrosive environments, see stainless steel socket set screws. For shaft applications requiring vibration resistance or protection of delicate shaft surfaces, see nylon tip socket set screws. For metric shaft assemblies, see alloy metric socket set screws (DIN 913–916). The full set screw selection and all socket fastener types are available through the Socket Set Screws and Sockets categories.

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