Grub Screws

Grub Screws

Grub screws — also known as set screws — are headless fasteners threaded along their entire length, used to secure a component (such as a pulley, gear, or collar) 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 of the component it secures, making it suitable for rotating applications where a projecting fastener head would be a safety or interference hazard. Grub screws are driven with an internal hex (Allen key) or slotted screwdriver and generate clamping or indentation force at their point end against the mating surface. AIMS Industrial supplies grub screws in standard metric sizes and point styles for engineering and industrial fastening applications.

Point Styles

The point style determines how the grub screw bears against the mating surface:

• Cup point: 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: A flat tip that bears on a flat surface or a flat ground into the shaft (a flat machined into the shaft is the correct practice for high-load applications). The flat point distributes load over a wider area than a cup point, reducing shaft surface damage where multiple positioning adjustments are required.
• Dog point (half dog): 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.
• Cone point: 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 is more important than shaft preservation.

Drive Types

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. Slotted grub screws are suited to light-duty applications and where an Allen key is not available.

Size Selection and Standards

Grub screws are specified by thread diameter and pitch (M3, M4, M5, M6, M8, M10, M12) and length. Standard metric grub screws are manufactured to DIN 913 (flat point), DIN 914 (cone point), DIN 915 (dog point), and DIN 916 (cup point). For grub screw selection by thread, length, and point style, contact our team.