Fasterner

Bolt & Nut Matching Guide

To ensure maximum joint integrity and prevent thread galling or failure, it is critical to match the correct bolt and nut materials. Below is our standard matching guide based on ASTM standards:

(Note: All fasteners are supplied with matching washers - e.g., ASTM F436 for structural or hardened washers for flange applications.)

To ensure perfect mating with flanges, valves, and equipment, all our fasteners are threaded strictly in accordance with international standards.

1. Common Thread Types

UNC (Unified National Coarse): The most widely used thread type in the US and global oil & gas industries. It is coarse and offers fast assembly. (Most common for flange bolts, e.g., 1/2"-13 UNC).

UNF (Unified National Fine): Features more threads per inch, providing higher tensile strength and better resistance to vibration. (Used in high-stress automotive and aerospace applications).

Metric (M): Follows ISO and DIN standards. Widely used in European and Asian markets. (e.g., M16 x 2.0).

BSW / BSP: British Standard Whitworth / British Standard Pipe. Used for specific legacy equipment and UK projects.

2. Threading Methods

Rolled Threads: We use thread rolling for most standard bolts. This process compresses the metal grain structure, making the threads up to 30% stronger and more fatigue-resistant than cut threads.

Machined Threads: Used for large diameters or special alloys where rolling is not possible, ensuring high precision.

2. Dimensional Tolerances (Class of Fit)

Class 2A / 2B: Standard commercial fit for most bolts and nuts, allowing for easy assembly with standard coatings.

Class 3A / 3B: A tighter precision fit for high-stress applications or when special coatings (like Xylan or PTFE) are applied.

Thread Inspection: 100% inspected using Go/No-Go ring and plug gauges to ensure perfect compatibility with your existing nuts and flanges.

Packaging & Logistics

We understand that fasteners must arrive at the job site in perfect condition. Our packaging solutions are designed to prevent thread damage, moisture, and loss during long-distance ocean transportation.

1. Inner Packaging

Standard Cartons: Bolts and nuts are packed in double-wall corrugated cartons. For heavy items, reinforced cartons or small wooden boxes are used.

Anti-Corrosion Protection: All fasteners are lightly oiled to prevent surface rust. For high-value or special-coated fasteners (like Xylan/PTFE), individual plastic bags are used.

Thread Protection: Stud bolts are equipped with plastic thread protectors on both ends to prevent damage to the threads during transport.

2. Outer Packaging

Wooden Pallets/Cases: Cartons are securely stacked on standard export wooden pallets or packed into fumigated wooden cases (ISPM 15 compliant).

Steel Strapping: Heavy-duty steel straps and stretch film are used to secure the pallets, preventing them from shifting or collapsing during transit.

Labeling: Each pallet/case is clearly marked with the product description, size, quantity, gross/net weight, and batch/heat number for full traceability.

3. Customized Packing Services

We offer Integrated Customized Services. We can print your company logo, product specifications, and unique barcodes on the cartons or labels based on your specific requirements. Mixed packing of bolts, nuts, and washers (Kits) is also available upon request.

4. Logistics & Delivery

Global Shipping: We have extensive experience in exporting to Europe, North America, the Middle East, and Southeast Asia. We can arrange Sea Freight (FCL/LCL), Air Freight, or Express delivery based on your timeline.

Documentation: We provide all necessary export documents, including Commercial Invoices, Packing Lists, Bill of Lading, and EN 10204 3.1 Mill Test Certificates.

Q1: What is the difference between B7 and B7M bolts?
A: Both are Chromium-Molybdenum alloy steel studs per ASTM A193. B7 is standard with a maximum hardness of 35 HRC. B7M is a modified version with a maximum hardness of 22 HRC, making it softer and more resistant to Sulfide Stress Cracking (SSC) in sour gas (H2S) environments.

Q2: How do I match the right nut with my bolts?
A: Matching is critical for joint integrity. As a standard rule:

A193 B7 studs must be matched with A194 2H nuts.

A320 L7 (low-temp) studs must be matched with A194 4 or 7 nuts.

A193 B8 (304) studs must be matched with A194 8 nuts.

A193 B8M (316) studs must be matched with A194 8M nuts.

(We can supply bolts, nuts, and washers as complete matched sets).

Q3: What coatings do you offer to prevent thread galling?
A: In high-temperature or highly corrosive environments, bare metal threads can seize (gall). We offer Xylan, PTFE, or Molybdenum Disulfide coatings. These provide a low-friction, corrosion-resistant layer that ensures accurate torque values during installation and allows for easy disassembly years later.

Q4: How do you ensure the quality of the threads and dimensions?
A: We maintain Strict Quality Control. We use rolled threads to increase fatigue strength by 30%. Every batch undergoes 100% Go/No-Go thread gauge inspection to ensure perfect mating. We also perform 100% PMI (Positive Material Identification) to verify the alloying elements. Third-party inspections (SGS, BV) are fully accepted.

Q5: Can you supply fasteners for extreme temperatures?
A: Yes. We supply A320 L7/L7M fasteners for cryogenic (low-temperature) service down to -101°C (ideal for LNG). For high-temperature service (up to 600°C) in power plants and refineries, we supply A193 B16 or B8 Class 2 fasteners.

Q6: How are the fasteners packaged to prevent damage during shipping?
A: We use export-standard packaging. Stud bolts are fitted with plastic thread protectors on both ends to prevent damage. Fasteners are packed in double-wall cartons, placed on fumigated wooden pallets, and secured with steel straps and stretch film to prevent shifting during ocean transit.