Machine Screws
Socket Head Cap Machine Screws 304 Stainless Steel Hex Drive Metric M3 M4 M5 For Industrial Equipment Assembly
What is a socket head cap machine screw?
A socket head cap screw is a type of cap screw with a cylindrical head and a hexagonal recessed drive. It is driven by an Allen key or hex driver. The internal wrenching design means the tool fits inside the head, so no external wrench clearance is required. This makes it ideal for assemblies where space is limited.
Key advantages
| Advantage | Why it matters |
|---|---|
| Internal hex drive | No external wrench clearance needed – fits tight spaces |
| Six‑point contact | Distributes torque evenly, reduces stripping risk |
| Higher tensile strength | Same size socket head is typically stronger than hex head bolt |
| Less counterbore required | Internal wrenching reduces installation depth |
| Clean cylindrical head | No protruding edges – safer and more compact |
| Higher torque capacity | Can be tightened more than Phillips or slotted drives |
Head variations in this family
| Head type | Best for |
|---|---|
| Standard socket head | Maximum tensile strength, general high‑load applications |
| Low socket head | 50% lower head height – thinner materials, limited clearance |
| Button head | Dome‑shaped, lower profile, lighter applications |
| Flange head | Built‑in washer collar, wider bearing surface, thinner materials |
| Vented head | Small hole through entire length – allows gas and fluid venting |
| Self‑locking head | Nylon patch bonded to threads – resists vibration loosening |
Material selection
| Material | Best for |
|---|---|
| 304 stainless steel | General corrosion protection, outdoor use |
| 316 stainless steel | Marine, saltwater, chemical exposure – contains molybdenum for superior corrosion resistance |
| Alloy steel Class 12.9 | Highest strength, heat treated, high tensile applications |
| Alloy steel Class 10.9 | High strength, general industrial use |
| Carbon steel | Cost effective, with zinc plating for mild protection |
Strength grades
| Grade | Tensile strength | Best for |
|---|---|---|
| Class 8.8 | 800 MPa | General industrial, moderate loads |
| Class 10.9 | 1000 MPa | Higher loads, demanding applications |
| Class 12.9 | 1200 MPa | Maximum strength, high tensile applications |
Surface finishes
| Finish | Best for |
|---|---|
| Plain / self‑colour | Standard, cost effective |
| Black oxide | Matte finish, mild corrosion protection |
| Zinc plated | Good rust and weather resistance |
| Passivated | Stainless steel, maximum corrosion resistance |
Where are they used?
- Industrial machinery and equipment assembly
- Automotive components and engines
- Electronics enclosures and server cabinets
- Mold and die construction
- Automation equipment and robotics
- Lighting manufacturing and aluminum profile construction
- Marine and outdoor equipment
- Aerospace and precision instruments
Quality
ISO 9001 and ISO 10012 certified. Precision thread rolling for smooth, burr‑free threads. Dimensional inspection and hardness testing on every batch.
Custom
Need non‑standard length, special material, or custom surface treatment? Send us your drawing or sample. We manufacture to your specification. OEM and ODM orders accepted.
FAQ
Q: What is the difference between a socket head cap machine screw and a hex head bolt?
A: Socket head cap screw has an internal hex drive – tool goes inside the head. Hex head bolt has external hex faces – tool goes around the head. Socket head requires less clearance and typically offers higher tensile strength than the same size hex head bolt.
Q: What tool do I need for a socket head cap screw?
A: An Allen key or hex driver. The size matches the socket diameter, not the head diameter.
Q: What is the strongest grade available?
A: Class 12.9 alloy steel. It is quenched and tempered for maximum tensile strength – ideal for high tensile applications.
Q: Can I use socket head cap screws outdoors?
A: Yes. Choose 304 stainless steel for general outdoor use, or 316 stainless steel for saltwater and coastal environments.
Q: Do you make custom socket head cap screws?
A: Yes. Send us your drawing or sample. We manufacture to your specification – custom lengths, special threads, and surface finishes available.
- Recessed hex socket drive – fits tight spaces
- Higher tensile strength than equivalent hex head bolts
- Standard, low, button, flange, vented, and self‑locking head variations
- 304 SS, 316 SS, and alloy steel Class 8.8/10.9/12.9
- Metric M3 to M16
- Black oxide, zinc plated, and passivated finishes
YH Fastener has been manufacturing precision fasteners since 1998. Our range includes socket head cap machine screws, self tapping screws, shoulder screws, and custom fasteners. ISO 9001 and ISO 10012 certified. Every batch inspected. Factory direct. Ship to 60+ countries.
