Trojan Special Fasteners Ltd | Specialist Nuts Fasteners | Nuts Bolts Washers | Precision Polygon Turning | Fastener Manufacturer

Frequently Asked Questions (FAQs)

Q: Can flange nuts be used in high-vibration environments?

A: Plain flange nuts provide improved vibration resistance compared to standard nuts due to increased bearing area and friction, but they are not classified as locking fasteners. For high-vibration applications, specify prevailing torque locking variants (nylon insert or all-metal locking types) or use supplementary locking methods such as anaerobic threadlockers, lock wire, or castellated nuts with split pins. Serrated flange nuts also provide enhanced vibration resistance by biting into the substrate surface.

Q: What is the difference between a serrated flange nut and a plain flange nut?

A: Serrated flange nuts feature radial teeth or serrations on the underside of the flange bearing surface. These serrations bite into the mating surface during tightening, creating additional friction and mechanical interlock that resists rotational loosening. Plain flange nuts have smooth bearing surfaces. Serrated variants are preferred for vibration-prone applications but may mark or damage decorative surfaces, powder coating, or soft materials.

Q: Can I reuse flange nuts?

A: Plain carbon steel and stainless steel flange nuts can generally be reused multiple times provided the threads are not damaged, cross-threaded, or deformed. Inspect threads visually and check for smooth engagement before reuse. Prevailing torque locking flange nuts (nylon insert or deformed thread types) may lose their locking effectiveness after initial use—inspect the prevailing torque feature and replace if compromised. Nylon insert nuts should typically be replaced after removal as thermal and mechanical cycling degrades the nylon ring.

Q: Are flange nuts suitable for outdoor applications?

A: Yes, flange nuts are excellent for outdoor applications when manufactured from appropriate materials with suitable surface treatments. For outdoor use, specify:

• 304 or 316 stainless steel for corrosion resistance
• Hot-dip galvanised carbon steel for structural applications
• Zinc-nickel or zinc flake coatings for automotive/industrial outdoor use

Avoid plain carbon steel with minimal coating in outdoor environments as corrosion will compromise performance.

Q: What size flange nuts does Trojan Special Fasteners manufacture?

A: Trojan Special Fasteners manufactures flange nuts from M3 to M52 in metric threads, 2BA to 2" in Imperial BSW/BSF threads, and #8 to 2.1/4" in Unified UNC/UNF threads. We also produce non-standard sizes, special thread forms (left-hand, multi-start, Acme, etc.), and completely bespoke designs to customer specifications.

Q: Can flange nuts be made with left-hand threads?

A: Yes, Trojan Special Fasteners manufactures left-hand threaded flange nuts for applications requiring reverse-rotation security (e.g., rotating machinery, bicycle pedals, propeller shafts). Left-hand threads are designated with "LH" suffix (e.g., M12 x 1.75 LH).

Q: Do you manufacture flange nuts to custom drawings?

A: Yes, Trojan Special Fasteners specialises in bespoke fastener manufacturing. We produce flange nuts to customer-supplied drawings and specifications including non-standard dimensions, special materials, unique flange geometries, combination features (e.g., flange + nylon insert + serrations), and proprietary designs. Our engineering team collaborates with clients to optimise designs for manufacturability and performance.

Q: What is the maximum temperature rating for nylon insert locking flange nuts?

A: Nylon 6.6 (polyamide) inserts have a maximum continuous service temperature of approximately 120°C (248°F). Above this temperature, the nylon begins to soften and lose its locking effectiveness. For higher temperature applications (>120°C), specify all-metal prevailing torque locking flange nuts which rely on deformed threads rather than polymer inserts.

Q: Can flange nuts be supplied with certification?

A: Yes, Trojan Special Fasteners provides material certification and test documentation as required. Available certificates include:

• Material test certificates (3.1 per EN 10204)
• Chemical composition analysis
• Mechanical property test results
• Dimensional inspection reports
• Traceability documentation with heat/lot codes

Certification requirements should be specified at the time of quotation.

Q: What surface treatments are recommended for marine environments?

A: For marine applications, we recommend:

• Submerged/splash zone: 316 stainless steel (no coating needed) or bronze
• Above waterline: 304 or 316 stainless steel, hot-dip galvanised carbon steel
• Coastal (salt air exposure): 316 stainless steel, zinc-nickel plated carbon steel, or 304 stainless with additional coating

Avoid plain zinc plating and aluminium in saltwater environments due to galvanic corrosion and rapid degradation.

Q: How do I determine the correct torque value for installation?

A: Installation torque depends on:

• Thread size and pitch
• Material grade (8.8, 10.9, stainless, etc.)
• Lubrication condition (dry, oiled, anti-seize, etc.)
• Required preload (clamping force)
• Friction coefficient of surface treatment

Consult torque reference charts specific to your fastener grade and lubrication condition. As a general rule, lubricated assemblies require approximately 20-30% less torque than dry assemblies to achieve equivalent preload. For critical applications, use calibrated torque wrenches and follow documented tightening procedures.

Q: Can Trojan Special Fasteners test prevailing torque on locking flange nuts?

A: Yes, we offer prevailing torque testing services. Supply us with the mating threaded component (bolt, stud, or internally threaded part) and we will conduct installation/removal torque tests to verify locking performance meets your specifications. Test results can be documented and certified as required.

Q: What is the lead time for bespoke flange nuts?

A: Lead times vary depending on order quantity, material availability, and manufacturing complexity. Standard catalogue items in common materials may be available from stock. Bespoke designs typically require:

• 1-2 weeks: Engineering review and quotation
• 2-4 weeks: Prototype/first article production
• 3-6 weeks: Full production batches

Contact our sales team for specific lead time estimates based on your requirements.

Q: What is the difference between a flange nut and a collar nut?

A: A flange nut has a wide circular flange at the base that extends outward beyond the hexagon body, providing maximum bearing surface area. A collar nut has a cylindrical collar section where the diameter is equal to or less than the across-flats dimension of the hexagon, providing a more compact profile. Flange nuts are better for maximum load distribution, whilst collar nuts are ideal for confined spaces or applications requiring alignment guidance from the collar.

Q: Can flange nuts be zinc plated?

A: Yes, carbon steel flange nuts can be zinc plated for corrosion protection. We offer clear zinc, yellow zinc, and black zinc plating options. Zinc plating typically provides 96-720 hours salt spray resistance depending on thickness. For enhanced corrosion protection, we recommend zinc-nickel plating (720+ hours) or hot-dip galvanising for outdoor structural applications. Stainless steel flange nuts do not require plating due to their inherent corrosion resistance.

Q: What thread types can you manufacture?

A: Trojan Special Fasteners manufactures flange nuts with metric threads (M3-M52), Imperial BSW/BSF threads (2BA-2"), and Unified UNC/UNF threads (#8-2.1/4"). We also produce special thread forms including left-hand threads, fine pitch threads, Acme threads, Buttress threads, square threads, multi-start threads, and completely custom thread profiles to customer specifications.

Q: Do you offer minimum order quantities?

A: Minimum order quantities vary depending on material, size, and specification complexity. For standard sizes in common materials (carbon steel, 304 stainless), we can accommodate small batch orders. Bespoke designs or exotic materials may require higher minimum quantities due to material procurement and setup costs. Contact our sales team to discuss your specific requirements—we're flexible and work with customers from prototype quantities through to high-volume production.

Q: Can you match an existing nut without a drawing?

A: Yes, if you can provide a physical sample, our engineering team can reverse-engineer the dimensions and produce matching flange nuts. We'll measure all critical dimensions (thread size, pitch, across-flats, flange diameter, height) and create a detailed drawing for your approval before manufacturing. For best results, provide 2-3 sample nuts to ensure accuracy and account for any manufacturing variations in the original parts.

Q: What is the difference between Grade 8.8 and Grade 10.9 nuts?

A: Grade 8.8 nuts have a minimum proof stress of 800 N/mm² and are suitable for general industrial applications with Grade 8.8 bolts. Grade 10.9 nuts have a minimum proof stress of 1000 N/mm² and are required for high-strength applications using Grade 10.9 or 12.9 bolts. Using Grade 8.8 nuts with Grade 10.9+ bolts may result in nut thread stripping before the bolt reaches full preload. Always match nut grade to bolt grade for balanced joint strength.

Q: Can flange nuts be passivated?

A: Yes, stainless steel flange nuts can be passivated to enhance their natural corrosion resistance. Passivation is a chemical treatment that removes free iron contamination from the surface and promotes formation of a chromium oxide passive layer. This is particularly important after machining operations. We can provide passivation per ASTM A967 or AMS 2700 specifications. Carbon steel flange nuts cannot be passivated as they lack sufficient chromium content.

Q: What is the torque-tension relationship for flange nuts?

A: The relationship between installation torque and bolt tension (preload) depends on multiple variables including thread pitch, material grade, surface treatment, lubrication, and friction coefficient. As a general approximation: Torque (N⋅m) = K × d × F, where K is the friction coefficient (typically 0.15-0.20 for dry assemblies, 0.10-0.15 for lubricated), d is the nominal bolt diameter (mm), and F is the desired preload (kN). For critical applications, use calibrated torque wrenches and follow documented tightening procedures with appropriate K-factor for your specific conditions.

Q: Do flange nuts meet automotive industry standards?

A: Yes, we manufacture flange nuts to automotive industry specifications including ISO, DIN, and proprietary OEM standards. For automotive applications, we typically supply Grade 10.9 or 12.9 carbon steel nuts with zinc-nickel or zinc-flake coatings for corrosion protection and no hydrogen embrittlement risk. We can provide PPAP documentation (Production Part Approval Process), material certifications, and dimensional inspection reports as required by automotive quality management systems.

Q: Can you manufacture flange nuts in small sizes for electronics?

A: Yes, we manufacture small-diameter flange nuts from M3 upwards, which are commonly used in electronics assembly, instrumentation, and precision equipment. Popular sizes for electronics include M3, M4, M5, and M6 in materials such as brass (for electrical conductivity), aluminium (for weight savings), and stainless steel (for corrosion resistance). We maintain tight tolerances essential for automated assembly and can provide clean, burr-free parts suitable for circuit board mounting.

Q: What is a serrated flange nut and when should I use one?

A: A serrated flange nut has radial teeth or serrations on the underside of the flange bearing surface. These serrations bite into the substrate during tightening, creating mechanical interlock and increased friction that resists vibration-induced loosening. Use serrated flange nuts in moderate-vibration applications, on softer materials (aluminium, plastics), or where cost-effective locking is needed without nylon inserts. Avoid serrated nuts on decorative surfaces, painted finishes, or very hard materials where the serrations cannot penetrate effectively.

Q: How does bar turning differ from cold forming for flange nuts?

A: Bar turning (our method) machines flange nuts from solid bar stock using CNC lathes, offering superior dimensional accuracy, tighter tolerances, excellent surface finish, and ability to produce complex geometries and non-standard sizes. Cold forming stamps nuts from wire or bar using dies under high pressure—it's faster for very high volumes but limited to standard sizes with looser tolerances. Bar turning excels for precision applications, bespoke designs, harder materials, and smaller production batches where quality outweighs pure volume efficiency.

Q: Can you provide material test certificates?

A: Yes, we provide material test certificates (also called mill test certificates or 3.1 certificates per EN 10204) documenting chemical composition, mechanical properties (tensile strength, yield strength, hardness), and heat/lot traceability. Certificates are available for most materials at a nominal surcharge. For critical applications (aerospace, medical, nuclear, pressure vessels), we can arrange 3.1 certification with full traceability from raw material supplier through finished component. Specify certification requirements when requesting quotation.

Q: What is the difference between UNC and UNF threads?

A: UNC (Unified National Coarse) threads have a larger pitch (fewer threads per inch) providing faster assembly, better performance in softer materials, and improved vibration resistance. UNF (Unified National Fine) threads have a smaller pitch (more threads per inch) offering greater thread engagement, higher tensile stress area, better locking performance, and suitability for precision adjustments. For example, 1/2" UNC has 13 threads per inch whilst 1/2" UNF has 20 threads per inch. Choose UNC for general applications, UNF for precision or high-strength requirements.

Q: Can flange nuts be anodised?

A: Aluminium flange nuts can be anodised to create a hard, durable, corrosion-resistant surface. Anodising creates an aluminium oxide layer that can be dyed various colours (clear, black, red, blue, gold) for identification or aesthetic purposes. The anodised layer is typically 5-25 microns thick and provides excellent wear resistance. Anodising is not applicable to steel, brass, or bronze nuts—these materials require different surface treatments such as plating, painting, or powder coating.

Q: What are the benefits of stainless steel over carbon steel?

A: Stainless steel flange nuts offer superior corrosion resistance without requiring additional surface treatments, making them maintenance-free in most environments. They're ideal for food processing, marine, chemical, and architectural applications. However, stainless steel has lower strength than heat-treated carbon steel (A2-70 stainless ≈ Grade 5.8 carbon steel), costs 3-5× more, and can suffer galling (thread seizure) during installation. Carbon steel with appropriate plating offers higher strength and lower cost but requires surface protection and may not be suitable for aggressive environments.

Q: Can you manufacture flange nuts with inspection holes?

A: Yes, we can incorporate inspection holes, witness holes, or tell-tale holes into flange nut designs. These features allow visual verification of thread engagement, bolt length, or preload indication without disassembling the joint. Inspection holes are commonly used in critical applications (aerospace, pressure vessels, structural connections) where joint integrity must be verified. Provide your dimensional requirements and we'll incorporate the feature into the manufacturing process.

Q: What is the recommended torque sequence for multiple flange nuts?

A: For assemblies with multiple flange nuts (such as flange joints, cylinder heads, or structural connections), follow a star or cross pattern tightening sequence starting from the centre and working outward. This ensures even load distribution and prevents warping. Use a multi-stage tightening procedure: first pass at 30% of final torque, second pass at 60%, third pass at 100%. Allow time between stages for joint relaxation. For critical applications, re-torque after initial operation or thermal cycling to account for embedment relaxation and settling.

Q: Do you offer custom flange diameters?

A: Yes, we manufacture flange nuts with custom flange diameters to suit specific applications. Standard flange diameters are typically 1.5-2.0× the across-flats dimension, but we can produce larger or smaller flanges as required. Larger flanges provide greater load distribution for soft materials or uneven surfaces, whilst smaller flanges reduce the radial footprint for space-constrained installations. Provide your required flange diameter and we'll verify manufacturability and quotation accordingly.

Q: Can flange nuts be supplied with locking patches or adhesives?

A: Yes, we can apply pre-applied adhesive patches (such as Nylok, Vibra-Tite, or equivalent) to flange nut threads. These microencapsulated adhesive patches activate during installation, creating a threadlocking effect that prevents loosening under vibration. Pre-applied patches offer convenience (no separate threadlocker application needed), clean assembly, consistent performance, and no mess compared to liquid threadlockers. They're suitable for temperatures up to 150°C and provide medium-strength locking that can be disassembled with hand tools.

Q: What flange thickness should I specify?

A: Standard flange thickness is defined by the applicable standard (ISO, DIN, ASME) and typically ranges from 1.5-4.0mm depending on nut size. Thicker flanges provide greater rigidity and load distribution but increase overall nut height and material cost. Thinner flanges reduce profile but may deform under high loads. For custom applications, consider substrate hardness (thicker flanges for softer materials), clamping loads (higher loads require thicker flanges), and clearance constraints (limited height requires thinner flanges). Our engineering team can recommend optimal flange thickness for your application.

Q: Can you manufacture flange nuts from customer-supplied material?

A: We can manufacture flange nuts from customer-supplied bar stock in certain circumstances, particularly for exotic materials or when the customer has existing material inventory. The material must be supplied in appropriate bar stock diameter with sufficient length for our turning operations. We'll require material certification and may perform incoming inspection to verify properties. Lead times may be shorter when material is customer-supplied, but pricing reflects machining operations only. Contact our sales team to discuss specific arrangements and technical requirements.