Grub Screws

A grub screw — also called a set screw or socket set screw — is a headless threaded fastener with no protruding head. It's driven fully into a tapped hole in a hub, collar, pulley or gear, and locks the component onto a shaft by friction and point engagement rather than by clamping two flanges together like a standard bolt. Because nothing sticks out, it's the right fastener choice anywhere a rotating assembly can't tolerate a projecting head. AIMS stocks grub screws in hex socket and slotted drive, cup and flat point, metric and imperial (UNC, UNF, BSW) threads, and alloy steel, A2/A4 stainless and nylon materials — from single packs through to assortment kits. Not sure which one suits your job? Our Grub Screw Guide: Cup, Dog, Flat Points & Allen Sizes covers selection in detail.

Point type — quick reference

The point is what actually grips the shaft. AIMS' range covers two point styles:

AIMS also stocks a knurled cup point option (a cup point with a fine knurl cut into the rim for extra bite) for higher-torque or vibration-prone joints.

Choosing the right grub screw

By point type

Cup point is the default pick for locking a pulley, collar or gear onto a shaft — it gives good resistance to both rotation and axial slip, and the small indent it leaves means the part can be removed and refitted in the same position. Reach for a knurled cup point where the joint sees higher torque or vibration. Flat point suits assemblies that get repositioned often, or shafts where you don't want the cup point's witness mark — plated or polished shafts, or softer metals.

By drive type

Hex socket (Allen key) drive is the standard across AIMS' range — it sits fully recessed, takes high torque without cam-out, and is the natural fit for a fastener with no head to grip. A slotted-drive option (DIN 551) is also stocked for older equipment or where a hex key isn't on hand — driven with a flat screwdriver instead.

By material and grade

High-grade alloy steel (plain, black or zinc finish) is the workshop standard where maximum clamping strength is needed and corrosion isn't a major concern. A2 (304) stainless suits indoor and mildly damp environments where rust would compromise the joint; A4 (316) stainless steps up to marine and chemical exposure, at somewhat lower strength than alloy steel. AIMS also stocks fully nylon grub screws — not a steel screw with a nylon tip, but a nylon-bodied fastener — for joints needing electrical insulation or a non-marring, non-conductive lock on a soft or plated shaft. Nylon carries a much lower load rating than steel, so match it to a light-duty joint.

Thread systems stocked

• Metric — common workshop sizes from M3 up to M12, matched to the tapped hole in the hub or collar.
• Imperial UNC (coarse) and UNF (fine) — UNC for general assembly, UNF where the finer pitch's extra vibration resistance is worth the slower fit.
• BSW (British Standard Whitworth) — an older imperial thread form still turning up on legacy Australian machinery; AIMS keeps stock across the common BSW range.

Always match the grub screw's thread diameter and pitch to the tapped hole exactly — metric and imperial threads aren't interchangeable even at a similar nominal size.

Common applications

Grub screws are specified wherever a component needs to be locked onto a shaft without a protruding fastener head: pulley and sprocket hubs, gears on shafts, shaft collars, motor and coupling hubs, adjustable knobs and levers, and machine adjustment settings. In any application subject to vibration, pair the grub screw with a threadlocker — see AIMS' threadlockers range — since the grub screw's holding torque alone isn't always enough to stop it backing out over time.

Assortment kits and refills

For workshops that need a spread of sizes on hand rather than single packs, AIMS stocks grub screw assortment kits and refill packs from Champion (metric and BSW kits, plus stainless assortments, each with a labelled cabinet drawer refill available separately) and Workshop Buddy grab kits (450-piece metric and imperial kits covering a wide size run in one box). These are the practical option for a maintenance van or store cage that needs to cover most jobs without stocking every size individually.

Brands stocked at AIMS

• Champion — grub screws, assortment kits and cabinet refills in metric, BSW and stainless.
• Hobson — Australian-made socket set screws across metric (DIN), UNC, UNF and BSW threads, including nylon and slotted options.
• Bremick — metric socket set (grub) screws in alloy steel, plain and cup point.
• Unbrako — high-tensile UNC knurled cup point socket set screws.
• Inox World — A2 (304) and A4 (316) stainless metric hex socket set screws.
• SOKO — metric knurled cup point socket set screws in alloy steel, zinc finish.
• Workshop Buddy — metric and imperial grub screw grab kits for the workshop or van.

Related ranges at AIMS

• Fasteners — the full AIMS fastener range
• Screws
• Hex set screws
• Socket head cap screws
• Stainless fasteners
• Shaft collars
• Threadlockers
• Fastener assortments
• Allen keys & hex screwdrivers

Frequently Asked Questions

What's the difference between a grub screw and a set screw?

None functionally — grub screw is the common Australian workshop name, set screw the more formal engineering term. Both describe the same headless, internally-driven fastener, and AIMS lists products under whichever name the supplier uses.

What point type should I use to lock a pulley or collar onto a shaft?

Cup point is the standard choice for general-purpose locking — it grips well on a plain shaft and leaves a small indent that helps the part go back in the same spot if refitted.

When would I use a flat point instead of a cup point?

When the assembly gets repositioned often, or when marking the shaft isn't acceptable — plated or polished shafts, or a softer shaft material.

What size grub screw do I need?

Match the thread diameter and pitch exactly to the tapped hole in the hub or collar. AIMS stocks metric sizes from M3 up to M12, plus imperial UNC, UNF and BSW threads across the common range.

What's the difference between UNC, UNF and BSW threads?

UNC (coarse) and UNF (fine) are Unified thread forms — UNF's finer pitch gives extra resistance to vibration loosening but takes longer to run down. BSW (British Standard Whitworth) is an older imperial thread standard with a different thread angle, still found on legacy Australian machinery.

Should I use alloy steel or stainless grub screws?

Alloy steel gives the highest clamping strength and suits most machinery where corrosion isn't a major concern. A2 (304) stainless handles indoor or mildly damp conditions; A4 (316) stainless steps up to marine and chemical exposure, though at somewhat lower strength than alloy steel.

What are nylon grub screws used for?

AIMS' nylon grub screws are fully nylon-bodied, not a steel screw with a nylon tip. They're used where a metal fastener would mark a polished or plated shaft, or where electrical insulation is required. They carry a much lower load rating than steel, so they suit light-duty joints only.

What drive type do grub screws use?

Hex socket (Allen key) drive is the standard across AIMS' range, giving high torque in a fully recessed fastener. A slotted-drive option is also stocked for older equipment or where a hex key isn't available.

Do grub screws need threadlocker?

In any application subject to vibration, yes — pair the grub screw with a threadlocker, since holding torque alone doesn't always stop it backing out over time.

Does AIMS sell grub screws individually or in kits?

Both — single packs by thread, size and point type, plus assortment kits and cabinet refill packs (Champion, Workshop Buddy) that cover a spread of metric or imperial sizes in one box.