Flange Bolts Manufacturer
MT.BOLTS manufactures Flange Bolts, which are externally threaded fasteners featuring an integrated flange under the hexagonal head that acts like a washer to distribute load. This design eliminates the need for a separate washer, improves clamping force, and prevents loosening. Flange bolts are widely used in automotive, heavy machinery, structural, and vibration-prone applications due to their high reliability and installation efficiency.
- System of Measurement: Metric (M3–M64) | Imperial (#4 to 2.5″)
- Length Range: 6 mm to 500 mm | 0.25″ to 20″
- Thread Pitch: Metric (Coarse/Fine) | UNC/UNF
- Thread Type: Full or partial thread
- Head Type: Hex Flange | Serrated Flange
- Finish Options: Plain, zinc-plated, hot-dip galvanized, passivated, or per customer requirement
- Standards:
- ASME B18.2.1 (Inch Flange Bolts)
- ASME B18.2.3.7M (Metric Flange Bolts)
- DIN 6921 / ISO 1665 (Hexagon flange bolts)
Flange Bolts Material Types
MT.BOLTS supplies carbon steel, stainless steel, duplex steel, and nickel-based alloy flange bolts, meeting the demanding requirements of chemical, marine, and high-temperature environments, compliant with various international standards.
| Material Category | Common Grades/Models | Description |
| Carbon Steel | ASTM A307, A325, A490 | High strength and cost-effective, suitable for general structures; requires anti-corrosion coating. |
| Stainless Steel | 304 (A2), 316 (A4), 321, 410 | Excellent corrosion resistance; widely used in food, chemical, and construction industries |
| Duplex Stainless Steel | UNS S31803/S32205 (F51), UNS S32750 (F53) | High strength with superior chloride corrosion resistance; used in seawater, petrochemical, and paper industries |
| Monel Alloys | Monel 400, Monel K500 | Excellent seawater corrosion resistance and mechanical strength; used in marine engineering and pump systems |
| Hastelloy Alloys | Hastelloy C276, C22, B2, X | Excellent resistance to strong acids and oxidizing media; widely used in chemical equipment and flue gas desulfurization |
| Inconel Alloys | Inconel 600, 625, 718 | Resistant to high temperature, pressure, and corrosion; used in heat exchangers, aerospace, and nuclear industries |
| Incoloy Alloys | Incoloy 800, 825, 925 | Ideal for high-temperature acidic environments; widely used in petroleum refining and heat treating systems |
| Nickel Alloys | Nickel 200, 201 | Pure or high-nickel alloys with excellent conductivity and alkali resistance; used in electronics and chemical applications |
Flange Bolts System of Measurement
- Metric: M3 to M64
- Imperial: #4 to 2.5″
- Length Range: 6 mm to 500 mm | 0.25″ to 20″
- Thread Pitch: Metric Coarse/Fine | UNC/UNF
- Thread Type: Full or partial thread
Flange Bolts Common Standards
- ASME B18.2.1 – Inch Hex Flange Bolts
- ASME B18.2.3.7M – Metric Hex Flange Bolts
- DIN 6921 / ISO 1665 – Hexagon Flange Bolts
- JIS B1189 – Japanese standard flange bolts (used in automotive)
Flange Bolts Surface Finishes
- Plain / Self-color: No surface treatment
- Zinc Plated (Blue/Yellow): Basic corrosion protection
- Hot Dip Galvanized (HDG): Thick zinc layer for outdoor use
- Black Oxide: For mild corrosion resistance and minimal reflectivity
- Passivated (Stainless Steel): Improves natural corrosion resistance
- PTFE / Xylan Coated: Used in chemical plants or marine environments
- Custom Coatings: Available on request, e.g., phosphate, chrome, cadmium
Why Choose MT.BOLTS
- Material Diversity
- Standardized Production
- Ample Inventory
- Competitive Pricing
- Low-MOQ Customization
Benefits and Limitations of Flange Bolts
Advantages
- Integrated flange distributes load, eliminating need for washers
- Serrated flange versions provide resistance to loosening under vibration
- Time- and cost-saving during installation
- High clamping force and consistent torque distribution
- Improved sealing over standard bolts in some designs
Disadvantages
- Not ideal for soft materials (serrated flange may damage surface)
- Larger head footprint may not fit in tight spaces
- Slightly more expensive than standard hex bolts
- Serrated versions may not be reusable
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Flange Bolts Applications
- Automotive industry (engine mounts, suspensions)
- Heavy machinery & earth-moving equipment
- Structural steel connections
- Agricultural equipment
- Pressure vessels and flanged piping connections
- Vibration-prone assemblies
FAQ About Flange Bolts
The flange acts as an integrated washer to distribute load and improve clamping efficiency.
Serrated flange bolts resist loosening under vibration, while non-serrated types are more surface-friendly.
Non-serrated types are reusable; serrated types may damage surfaces and lose grip if reused.
Yes, that’s one of their main benefits — the flange replaces the need for a washer.
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