Stainless Steel Socket Head Cap Screw
Specification
Stainless Steel Socket Head Cap Screws | Metric Sizes
For assemblies where a wrench cannot easily reach the sides of a fastener, an internal hex drive provides access along the screw axis. PO JUN offers stainless steel socket head cap screws in metric sizes M3–M20, with lengths from 4 to 150 mm depending on diameter.
The cylindrical head and hex socket make these screws a practical choice for machine components, mounting brackets, fixtures, and equipment assemblies. Also commonly called stainless steel Allen screws, they work with matching tapped holes or nuts and can be installed or removed using a suitable hex key or driver bit.
Hex Socket Access for Machinery and Equipment
Installation Where Side Clearance Is Limited
The tool engages inside the head rather than around its outside. This can simplify fastening between adjacent components where an external hex head would require additional wrench or socket clearance.
Cylindrical Head with a Flat Bearing Surface
The head seats against the mounting surface to clamp the assembly. It normally remains above the component; where a recessed installation is needed, a correctly sized counterbore can accommodate the head.
Sizes for Small Components and Deeper Assemblies
The range covers short screws for compact parts and selected lengths up to 150 mm for thicker assemblies. Buyers can review multiple fastening positions within the same product range rather than choosing by head style alone.
Stainless Steel Socket Head Cap Screw Specifications
Available Metric Sizes
All lengths below are in mm.
| Thread Diameter | Available Lengths (mm) |
|---|---|
| M3 | 4, 5, 6, 8, 10, 12, 16, 20, 25, 30, 35, 40, 45, 50 |
| M4 | 4, 5, 6, 8, 10, 12, 16, 20, 25, 30, 35, 40, 45, 50, 55, 60 |
| M5 | 5, 6, 8, 10, 12, 16, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70 |
| M6 | 8, 10, 12, 16, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 80, 90, 100 |
| M8 | 10, 12, 16, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 80, 90, 100, 110, 120, 130, 140, 150 |
| M10 | 16, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 80, 90, 100, 110, 120, 130, 140, 150 |
| M12 | 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 80, 90, 100, 110, 120, 130, 140, 150 |
| M14 | 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 80, 90, 100 |
| M16 | 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 80, 90, 100, 110, 120, 130, 140, 150 |
| M20 | 35, 40, 45, 50, 55, 60, 65, 70, 80, 90, 100, 110, 120, 130, 140, 150 |
Length is normally measured from the bearing surface under the head to the tip. Thread pitch, thread coverage, and material grade should be confirmed for the selected size.
Where Socket Head Cap Screws Are Used
These fasteners suit assemblies that allow space for the cylindrical head and access for a hex tool.
- Automation equipment: Attach brackets, sensor mounts, and modular components where neighboring parts limit side access.
- Jigs and fixtures: Fasten plates and stops, with counterbored mounting positions where the head must sit below the working surface.
- Machinery assemblies: Connect housings, mounting blocks, and equipment components that require access during servicing.
- Instrument and control equipment: Secure compact mechanical parts where a defined head size and removable threaded connection are needed.
For load-bearing joints, select the screw’s mechanical properties and thread engagement to match the application rather than relying on diameter alone.
Choosing the Right Fit
Match the screw to the mating thread first, then check length and head clearance. For blind tapped holes, allow sufficient thread engagement without letting the screw bottom out before the joint is clamped.
Stainless steel grade should reflect the operating environment. Moisture, cleaning chemicals, salt exposure, and contact with other metals can influence material selection. If your drawing specifies a grade, property class, or dimensional standard, include it with the inquiry so the required product can be reviewed.
For longer screws, confirm whether the assembly needs full threads or an unthreaded shank. This is particularly important when the shank passes through several components or serves a locating function.
Request Pricing for Your Assembly
Send PO JUN your diameter, length, thread pitch, stainless steel grade, and order quantity. A drawing or existing part reference is helpful for replacement purchases and repeat production orders.
You can include several sizes in one inquiry, together with the destination country and requested delivery date. If your order requires specific packaging, labels, or inspection documents, mention these when requesting a quotation.
Share your drawing or size list to discuss the socket head cap screws needed for your next production run.
Frequently Asked Questions
Can I use a countersunk screw in the same mounting hole?
Not without checking the seating geometry. A socket head cap screw uses a flat bearing surface, while a countersunk screw needs a matching tapered seat. They are not direct substitutes based only on thread diameter and length.
Does stainless steel automatically mean a high-strength screw?
No. Material grade and mechanical properties are separate purchasing considerations. For a joint with a specified load, identify the required property class or mechanical standard.
How can I reduce galling when using stainless steel nuts?
Keep mating threads clean, avoid forcing misaligned parts, and control installation speed. An approved lubricant or anti-seize treatment may help, but the tightening torque must account for the changed friction conditions.
Can I select the hex key size from the thread diameter alone?
Use the screw’s dimensional drawing or applicable standard to confirm the socket size. The correct driver fit helps reduce socket damage during installation and removal.