Grub Screws

Grub Screws (Set Screws)

Grub screws — also known as set screws — are headless threaded fasteners used to secure a component such as a pulley, gear, collar, encoder or knob to a shaft, or to fix one part against another surface. Without a protruding head, a grub screw can be recessed fully below the surface, making it suitable for rotating applications where a projecting fastener head would be a safety or interference hazard. Driven with an internal hex (Allen) key or slotted screwdriver, the screw generates clamping or indentation force at the point end against the mating surface.

AIMS Industrial supplies grub screws in standard metric sizes M3 to M12 across all four common point styles, in stainless steel and high-tensile alloy grades. Manufactured to ISO 4026 (flat), ISO 4027 (cone), ISO 4028 (dog) and ISO 4029 (cup) — equivalent to DIN 913, 914, 915 and 916 respectively.

Point styles

The point style determines how the grub screw bears against the mating surface and how repositionable the assembly is:

• Cup point (ISO 4029 / DIN 916) — the most common general-purpose point. A small concave cup at the tip bites into the shaft surface, providing good resistance to rotation and axial movement. The indentation left in the shaft allows the pulley or collar to be repositioned precisely if removed and refitted.
• Flat point (ISO 4026 / DIN 913) — a flat tip that bears on a flat surface or a flat ground into the shaft (machining a flat into the shaft is the correct practice for high-load applications). Distributes load over a wider area than a cup point, reducing shaft surface damage where multiple positioning adjustments are required.
• Dog point / half-dog (ISO 4028 / DIN 915) — a short cylindrical extension at the tip that locates into a drilled hole or slot in the shaft. Provides positive location and high resistance to axial movement. Used where accurate, repeatable positioning between the shaft and the hub is required — common in encoder mounts and indexing applications.
• Cone point (ISO 4027 / DIN 914) — a sharp conical tip that penetrates deeply into the shaft surface for maximum grip. Used in permanent or semi-permanent assemblies where maximum locking force matters more than shaft preservation.

Drive types & materials

Socket (hex/Allen) drive is the standard for metric grub screws in engineering applications — the internal hex allows high tightening torque in the recessed position. AIMS stocks grub screws in:

• Class 12.9 alloy steel (black oxide) — the standard high-tensile industrial grub screw. Suits most machinery and drivetrain applications.
• A2-70 stainless (304) — for indoor and lightly corrosive environments where rust would compromise the assembly.
• A4-80 stainless (316) — for marine, food processing and aggressive chemical environments.

Slotted grub screws are suited to light-duty applications and where an Allen key is not available — less common in modern engineering use.

Common applications

Grub screws are specified across pulley and sprocket hubs, gear-on-shaft fixing, shaft collars, encoder mounts, motor coupling hubs, hose-clamp adjustment, knob and lever retention, and bearing locking collars. For high-vibration applications, a grub screw is typically paired with a thread-locker (medium-strength threadlocker for service-disassembly assemblies, high-strength for permanent fixings).

Size selection & standards

Grub screws are specified by thread diameter and pitch (M3, M4, M5, M6, M8, M10, M12) and length. As a rule of thumb, choose a screw length 1.5–2× the thread diameter for adequate engagement in the hub or collar. Stocked metric sizes follow the ISO 4026–4029 / DIN 913–916 standards across both stainless and high-tensile grades.

Browse the wider fastener range

Grub screws sit within our broader fastener range. For the full set screw and machine screw family, see hex set screws, socket head cap screws and machine screws. For stainless options across all fastener types, see stainless fasteners. For background on socket-drive fasteners, torque values and grade selection, see our socket head cap screw guide.

For grub screw selection by thread, length and point style, call (02) 9773 0122 or contact our team.