A set screw (also called a grub screw) is a headless fastener threaded along its full length and driven by an internal socket. Its job is to lock one part against another — most often a hub, collar, gear or pulley onto a shaft — without any part of the fastener sticking out. The secret to using set screws well is choosing the right point, because the tip is what actually does the holding.
How Set Screws Work
A set screw threads through a tapped hole in the outer component and presses its point against the inner shaft. The resulting clamping and, in some cases, biting action prevents rotation and axial movement. Because there is no head, the screw sits flush or recessed, keeping the assembly compact and snag-free.
Point Types and Their Uses
- Cup point — the most common. A recessed ring edge bites slightly into the shaft, giving strong holding for general use. Best on harder shafts where a small mark is acceptable.
- Cone point — a sharp cone that digs into a matching spot-drilled dimple, providing the highest resistance to movement. Ideal for permanent or high-torque settings.
- Flat point — a flat tip that presses without marring the shaft. Good for frequent adjustment or soft shafts, and where the screw seats against a flat or pre-machined pad.
- Dog point — a protruding cylindrical tip that fits into a hole or slot in the shaft, acting as a locating pin as well as a lock.
- Oval point — a rounded tip that allows the screw to press against an angled or curved surface and permits some adjustment.
Point Selection Table
| Point | Holding Power | Shaft Damage | Best For |
|---|---|---|---|
| Cup | High | Minor mark | General purpose |
| Cone | Very high | Deep bite | Permanent settings |
| Flat | Moderate | None/minimal | Adjustable, soft shafts |
| Dog | High + locating | Needs matching hole | Indexing, alignment |
| Oval | Moderate | Minimal | Angled surfaces |
Material and Strength
Set screws are commonly made from hardened alloy steel (typically grade 45H) for maximum holding, or stainless steel A2/A4 for corrosion resistance in food, marine and outdoor equipment. The alloy steel versions are heat treated so the point stays hard enough to grip without deforming.
Installation Tips
- For maximum security, use two set screws at 90° or 120°, or a cone point into a drilled dimple.
- Apply thread locker on high-vibration assemblies to stop the screw backing out.
- Do not over-torque small set screws — the hex socket can round out.
Ordering the Right Set Screws
Specify diameter and pitch, length, point type, material and drive when ordering. A source factory can supply the full range of point styles in steel and stainless, including non-standard lengths, so your hubs, collars and couplings lock exactly as designed.
About Chaoshuo Trading
Chaoshuo Trading is a source fastener factory in China, offering factory-direct pricing and full OEM/ODM customization on bolts, nuts, screws, washers and anchors. From standard DIN/ISO/ANSI parts to custom drawings, we manufacture to your spec with in-house quality control and export-ready packaging. Get a fast quote today:
- Email: info@chaoshuotrade.com
- WhatsApp: +86 158 0311 9164
- Website: www.chaoshuotrade.com