Socket Head Cap Screw ASME B18.3 Carbon Steel Zinc Plated

Socket Head Cap Screw ASME B18.3 Carbon Steel Zinc Plated, also widely called Hex Socket Bolt or Allen Bolt, is an inch-series internal hex fastener manufactured strictly following ASME B18.3 standard. Made of premium carbon steel and finished with blue white zinc plating, this Allen screw balances reliable mechanical strength and moderate corrosion resistance.

Its compact cylindrical cup head is designed to sit neatly inside counterbored holes, which saves valuable space for tight-fit assemblies. We maintain stock of a full range of UNC thread sizes and multiple lengths. Alternative surface treatments including yellow zinc, black oxide and stainless steel are available on request. It is a preferred fastening solution for machinery, molds, equipment frames and various metal fabrication projects.

Core Product Features

- Complies with ASME B18.3 inch standard, UNC coarse thread

- High-quality carbon steel substrate with good tensile performance

- Blue white zinc plated finish for rust protection

- Internal hexagon drive, compatible with standard Allen wrenches

- Cylindrical socket cap head for counterbore installation

- Precision thread rolling, tight and consistent dimensional tolerance

- Multiple lengths and surface finishes for selection

- Standard bulk packing, OEM & custom service available

- Stable locking performance, not easy to loosen under vibration

Product Specifications

Production Flow

We control quality from raw material to finished goods. The full production process includes raw wire inspection, cold heading, thread rolling, heat treatment, electroplating, sorting and final QC check.

Heat treatment optimizes hardness and mechanical strength. Rolled threads have smooth, complete tooth profile without cracks. The zinc plating layer is uniform with minimal burrs. Visual sorting removes defective pieces before packing.

Typical Applications

- Automation machinery and equipment assembly

- Mold, fixture and tooling fastening

- Industrial metal frames, cabinets and supports

- Mechanical accessory assembly

- Internal fixing of electrical and metal enclosures

- General metal fabrication and engineering projects

Installation Guidance

Use a properly sized Allen wrench to drive the screw, prevent wrench slipping and hex socket damage. Machine a matched counterbore if you require the head to sit flush below the surface. Control tightening torque properly; over-torque will cause thread stripping or head breakage. Blue white zinc finish works best for indoor or dry outdoor conditions. For coastal or heavily corrosive environments, stainless steel or Dacromet finish is recommended.

Surface Finish Comparison Table

How to Choose The Right Size

Three key factors to confirm before ordering:

1. Thread size: ASME B18.3 is inch UNC thread, not interchangeable with metric DIN912 socket screws.

2. Screw length: The effective length must cover the total thickness of clamped parts and keep sufficient thread engagement.

3. Counterbore dimension: Make sure the counterbore diameter and depth can accommodate the cylinder head completely.

Quality Assurance

Multi-stage inspection runs through the whole production: incoming raw material test, in-process dimension & hardness check, finished product salt spray and torque test, and random sampling before shipment. Test certificates can be provided upon your requirement.

Compare With Other Common Screw Heads

Pan Head: Shallow round head, cannot sink into counterbore, exposed after installation. Truss Head: Extra wide and low-profile head, used for distributing pressure on thin sheet. Flat Head: Countersunk, sits flush on the surface without protruding. Socket Cap Head: Vertical cylinder head, designed specially for counterbore holes, high torque resistance.

FAQ

Q1: Can ASME B18.3 socket cap screws replace metric DIN912 screws?

A: No. ASME B18.3 belongs to inch UNC system, thread pitch and dimensions differ from metric DIN912, they are not interchangeable.

Q2: Can I mix different sizes and finishes in one order?

A: Yes, mixed orders for regular sizes are supported, MOQ can be discussed.

Q3: Can you supply salt spray test reports?

A: We can provide salt spray reports as requested, and adjust plating time to meet your target salt spray hours.

Q4: What is your standard packing method?

A: Standard packing is cartons with inner poly bags, each carton with specification labels. Custom packing is acceptable.

Our Strengths

We are a professional fastener manufacturer with rich experience supplying inch fasteners to North America and Latin America markets. Strict QC, stable batch quality and competitive pricing are our advantages. Regular stock items enjoy short lead time.

Shipping & Trade Terms

Stock items can be ready for shipment within 7–15 working days. Sea freight, air freight and express delivery are available. We support FOB, CIF and DAP terms. Reinforced packing is used for sea transport to avoid transit damage. Commercial invoice, packing list and certificate of origin can be supplied.