Frequently Asked Questions (FAQ) About Nylon Insert Nuts

Section 1: General Understanding & Terminology

1. What is the difference between a nyloc nut and a nylock nut?
There is no technical difference - these are simply alternate spellings of the same product type. Both terms refer to nylon insert lock nuts. The variation arose from different manufacturers' trademarking attempts. "Nyloc" was a prominent early brand name that became genericised. The technically correct term is "nylon insert lock nut" or "nylon insert prevailing torque nut," but nyloc, nylock, elastic stop nut, and aircraft lock nut are all widely used synonymously throughout the industry.
2. Are nylon insert nuts the same as self-locking nuts?
Nylon insert nuts are one specific type within the broader category of self-locking nuts. Self-locking nuts encompass any nut design that resists loosening without external locking devices (such as lock washers, cotter pins, or safety wire). This includes all-metal distorted thread nuts, elliptical top lock nuts, centre lock nuts with crimped inserts, and polymer insert nuts. Nylon insert nuts represent the most common self-locking nut type for moderate temperature applications due to their reliability and cost-effectiveness.
3. What does "prevailing torque" mean?
Prevailing torque is the measurable rotational resistance experienced when turning a nut onto a bolt before the nut contacts the bearing surface (the "running torque") and after it lifts off the bearing surface during removal (the "breakaway torque"). This resistance, typically ranging from 0.5 to 5 Nm depending on size, indicates the locking mechanism is functioning. Specifications establish minimum and maximum prevailing torque values that must be maintained throughout the nut's service life to ensure reliable locking performance.
4. Why are nylon insert nuts called aircraft lock nuts?
Early aerospace applications drove nylon insert nut development in the 1940s-1950s when aircraft designers sought reliable vibration-resistant fasteners for safety-critical assemblies. Military and commercial aircraft subjected fasteners to intense vibration, temperature variation, and dynamic loading. Nylon insert nuts proved exceptionally effective, earning widespread adoption throughout aerospace industries. Military specifications (MS, NAS, AN) formalised their use, cementing the "aircraft lock nut" designation. Today they're equally common in automotive, marine, and industrial applications.
5. What is Nylon 66 and why is it used?
Nylon 66 (Polyamide 6,6) is a semi-crystalline thermoplastic polymer formed through polycondensation of hexamethylene diamine and adipic acid. Its molecular structure provides excellent mechanical properties including high tensile strength (70-85 MPa), good impact resistance, dimensional stability across moderate temperatures, and resilience after compression - ideal characteristics for a locking insert. The material designation "66" refers to six carbon atoms in each of the two molecular precursors. Nylon 66 offers superior temperature resistance compared to Nylon 6, making it the preferred polymer for prevailing torque applications.
6. Can nylon insert nuts be used underwater or in marine environments?
Yes, nylon insert nuts perform excellently in marine environments when manufactured from appropriate corrosion-resistant materials. For saltwater applications, specify stainless steel (A4-316) or bronze nuts with nylon inserts. The polyamide insert absorbs minimal moisture (approximately 1-2% water absorption at saturation), causing negligible dimensional change. Nylon actually provides beneficial galvanic isolation between dissimilar metal threads, preventing electrolytic corrosion. Marine-grade nylon inserts resist most marine fuels, lubricants, and bilge contaminants. Trojan manufactures extensive ranges of marine-spec nylon insert nuts for yacht builders, commercial vessels, and offshore installations.
7. What's the difference between a nylon insert nut and a nylon lock nut?
These terms are interchangeable - both refer to the same product. The fastener industry uses various nomenclature including nylon insert nut, nylon lock nut, nylon locking nut, nylon insert lock nut, and elastic stop nut. All describe a hexagon nut containing a captive nylon collar that creates prevailing torque against bolt threads. Consistency in terminology isn't universal, but "nylon insert nut" or "nylon insert lock nut" represents the most technically precise description used in international standards such as BS EN ISO 7042.
8. How are nylon insert nuts different from lock washers?
These represent fundamentally different locking philosophies. Lock washers (split washers, spring washers, or toothed washers) attempt to maintain bolt tension through spring action or bite into adjacent surfaces, but numerous studies demonstrate they provide minimal vibration resistance. Nylon insert nuts create continuous frictional interference between threads throughout the engaged length, physically preventing nut rotation even when joint preload relaxes. Testing consistently shows nylon insert nuts dramatically outperform lock washers in vibration testing. For critical applications requiring reliable anti-loosening performance, nylon insert nuts are categorically superior.

Section 2: Technical Specifications & Standards

9. What standards govern nylon insert nut manufacturing?
Multiple international standards specify dimensional, mechanical, and performance requirements. Primary British/European standards include BS EN ISO 7042 (metric coarse), BS EN ISO 7040 (metric fine), BS EN ISO 10511/10512 (thin nuts), and BS 1768 (Imperial sizes). American standards include ASME B18.16.6 and ASTM F836. Military/aerospace specifications include MIL-DTL-18240, MS17825/17826, and NAS679. German DIN 985/982/986 remain widely referenced despite ISO supersession. Each standard prescribes specific dimensions, tolerances, thread classes, material grades, prevailing torque ranges, proof loads, and testing protocols.
10. What is the difference between ISO 7040 and ISO 7042?
ISO 7042 specifies nylon insert nuts for metric coarse pitch threads (standard thread pitch for each diameter), whilst ISO 7040 covers metric fine pitch threads (closer thread spacing). Fine pitch threads provide greater thread engagement per unit length, useful in thin-wall applications or when maximum thread strength is required. Both standards define identical hexagon across-flats dimensions and nut heights for corresponding thread sizes but differ in thread pitch specifications. For example, M10 ISO 7042 specifies 1.5mm pitch whilst M10 ISO 7040 covers 1.25mm and 1.0mm fine pitches.
11. Are DIN 985 and ISO 7042 interchangeable?
Functionally yes, dimensionally yes with minor tolerance variations. DIN 985 was the original German national standard for metric coarse nylon insert nuts, later superseded by ISO 7042 which harmonised dimensions across European nations. Current BS EN ISO 7042 represents the British adoption of this international standard. Nuts manufactured to DIN 985 typically meet ISO 7042 requirements and vice versa. However, formal approval or aerospace applications may require explicit specification compliance documentation. When substituting, verify that tolerance bands, material grades, and prevailing torque values satisfy application requirements.
12. What thread classes are used for nylon insert nuts?
Most nylon insert nuts employ Class 6H internal threads (ISO metric) or Class 2B threads (Unified), representing free-running fits with moderate clearance. These thread classes permit easy nut starting whilst the nylon insert provides locking action. Tighter thread classes would increase installation torque excessively and risk thread galling. Aerospace applications may specify Class 3B threads for precision fit. The external thread (bolt or screw) typically uses Class 6g (ISO) or Class 2A (Unified). Left-hand thread variants maintain the same class designations with opposite helix direction.
13. What are the material grade requirements for structural applications?
Grade 8 (metric) or Grade 5 (Imperial) represents the minimum specification for structural steel applications. Grade 8 requires minimum 800 MPa tensile strength with 640 MPa proof load. High-strength applications demand Grade 10 (1040 MPa) or Grade 12 (1220 MPa) materials. Stainless steel structural applications typically specify A4-70 or A4-80 grades (700 or 800 MPa). Aerospace applications often require custom alloy specifications with full traceability and material certification. Trojan maintains extensive material inventory across standard and high-strength grades.
14. Do nylon insert nuts require specific torque specifications?
Yes. Installation torque for nylon insert nuts must account for both the prevailing torque (locking resistance) and the desired clamp load. The total installation torque typically runs 20-100% higher than equivalent plain nuts. Standard torque tables must be adjusted upward, or application-specific testing performed to establish correct values. Over-torquing risks damaging the nylon insert or stripping threads; under-torquing fails to achieve adequate clamp load. Critical applications require calibrated torque wrenches and documented torque values. Trojan can provide application engineering support to establish appropriate torque specifications for specific assemblies.
15. What is the proof load for a nylon insert nut?
Proof load represents the maximum tensile stress a nut must withstand without thread stripping or permanent deformation. For metric Grade 8 nuts, proof load equals 640 MPa times the stress area. For example, an M10 Grade 8 nylon insert nut must support approximately 46.5 kN (4,750 kgf) without failure. The nylon insert does not significantly affect proof load capacity - the metallic thread engagement determines strength. Testing involves threading the nut onto a mandrel and applying specified tensile load; the nut must not strip or show permanent deformation. Proof loads are tabulated in relevant standards for each thread size and material grade.

Section 3: Materials, Finishes & Coatings

16. What material should I specify for outdoor applications?
For outdoor exposure combining moisture, UV radiation, and temperature cycling, specify A4-316 stainless steel (marine-grade austenitic stainless) with passivated finish. This material provides excellent atmospheric corrosion resistance without coating dependence. For high-strength outdoor applications where stainless steel is insufficient, use carbon steel or alloy steel with hot-dip galvanising (85 microns minimum) or Geomet/Dacromet ceramic coating. Avoid electroplated zinc in aggressive outdoor environments - it provides limited protection. The nylon insert itself demonstrates good UV resistance, though prolonged direct sunlight exposure may cause slight embrittlement over years.
17. Are stainless steel nylon insert nuts magnetic?
Depends entirely on the stainless steel grade. Austenitic grades (A2-304, A4-316) are non-magnetic in annealed condition, useful where magnetic interference must be avoided (medical equipment, instrumentation, compass proximity). However, cold working during thread forming can induce slight magnetism. Martensitic stainless grades (410, 420) and precipitation-hardening grades (17-4PH) are magnetic. If non-magnetic behaviour is critical, specify A4-316 in annealed condition and verify with testing. Some applications actually require magnetic fasteners for retrieval purposes - inform Trojan of your specific magnetic property requirements.
18. Can you supply nylon insert nuts in bronze or specialist copper alloys?
Yes. Trojan manufactures nylon insert nuts in various bronze and copper alloy grades including phosphor bronze (PB102), aluminium bronze (CA104), nickel silver (NES833), and other specialist materials. These materials offer excellent corrosion resistance, good electrical and thermal conductivity, and non-sparking properties important for hazardous environments. Bronze nuts are particularly popular in marine applications, electrical engineering, and industries requiring non-magnetic, non-sparking fasteners. Lead times may be extended for specialist materials depending on availability.
19. What is the difference between zinc plating and hot-dip galvanising?
Zinc plating (electroplating) deposits 5-25 micron zinc layers through electrolytic process, providing decorative finish and moderate corrosion protection (typically 200-500 hours salt spray resistance). Hot-dip galvanising immerses parts in molten zinc at 450°C, creating 50-150 micron metallurgically-bonded coating offering 1000+ hours salt spray protection. Galvanised nuts have rougher appearance, thicker coating (affecting thread dimensions), and superior longevity. Galvanising suits outdoor structural applications; zinc plating suits automotive and general industrial use. For nylon insert nuts, verify the galvanising temperature profile doesn't degrade the polymer insert - Trojan uses controlled processes preserving insert integrity.
20. What is cadmium plating and when is it specified?
Cadmium plating provides exceptional corrosion protection with excellent electrical conductivity and low friction characteristics, explaining its historical aerospace dominance. However, cadmium is highly toxic, environmentally hazardous, and increasingly restricted under RoHS and REACH regulations. It remains permissible in aerospace and defence applications where safety-critical performance justifies use. Cadmium plating provides superior performance in marine atmospheres compared to zinc. If your application specifies cadmium-plated fasteners (common in legacy aerospace designs), Trojan can supply to MIL-DTL-870 specifications, though we recommend exploring zinc-nickel or IVD aluminium alternatives where permissible.
21. What does passivation do for stainless steel nuts?
Passivation chemically removes free iron contamination from stainless steel surfaces and promotes formation of a dense chromium oxide protective layer. Manufacturing processes (machining, thread rolling) can embed steel tool particles onto stainless parts, creating corrosion initiation sites. Passivation using nitric or citric acid baths dissolves these contaminants whilst leaving the chromium-rich stainless steel matrix intact. The resulting chromium oxide film provides the corrosion resistance that defines stainless steel. All Trojan stainless steel nylon insert nuts receive passivation treatment per ASTM A967 unless otherwise specified, ensuring maximum corrosion performance.
22. Can nylon insert nuts be painted or powder coated?
Yes, but with important considerations. The nylon insert must be protected during the coating process to prevent polymer degradation from heat or chemical exposure. Powder coating typically requires 180-200°C curing temperatures, potentially damaging standard Nylon 66 inserts rated to 120°C continuous. Solutions include: masking the internal threads and insert during coating; installing inserts after coating (requires post-coating assembly capability); using high-temperature polymer inserts; or applying liquid paint with lower cure temperatures. For aesthetic matching in assemblies, Trojan can coordinate coating application ensuring the locking function remains uncompromised.

Section 4: Temperature Performance & Environmental Resistance

23. What is the maximum temperature for nylon insert nuts?
Standard Nylon 66 inserts provide reliable locking function for continuous operation up to 120°C (248°F). Short-term exposure to 150°C is generally acceptable for limited durations. Beyond 120°C continuous, the nylon begins softening, reducing prevailing torque and potentially causing creep or dimensional change. For applications between 120-180°C, Trojan can supply nuts with high-temperature polyamide or polyimide inserts. Above 180°C, transition to all-metal prevailing torque nuts (distorted thread, crimped collar, or spring tab designs) becomes necessary. Always consult application engineering when operating temperatures approach insert material limits.
24. Do nylon insert nuts work in freezing temperatures?
Yes, excellent performance in cold environments. Nylon 66 actually becomes stronger and stiffer at reduced temperatures, increasing prevailing torque slightly. Testing demonstrates reliable function to -55°C and below. Cold temperature embrittlement is not a concern within normal industrial temperature ranges (-40°C to +120°C). Arctic, Antarctic, and cryogenic applications routinely employ nylon insert nuts successfully. The greater challenge in extreme cold involves differential thermal contraction between the nut, bolt, and joint materials - ensure adequate preload to maintain clamp force through thermal cycling. Trojan has supplied nylon insert nuts for polar research equipment, refrigeration, and LNG applications.
25. What happens if a nylon insert nut gets too hot during service?
Excessive temperature exposure degrades the nylon insert through thermal aging processes. Initial symptoms include reduced prevailing torque as the polymer softens. Prolonged overheating causes molecular chain scission, irreversibly destroying the polymer's mechanical properties. The insert may discolour (yellowing or browning), become brittle, or completely lose resilience. Once thermally damaged, the nut cannot recover - replacement is mandatory. Applications involving periodic thermal spikes (engine components, brake systems) require careful evaluation. If you suspect temperature-related degradation, measure prevailing torque - values below specification minimums indicate the nut should be replaced.
26. Are nylon insert nuts resistant to oil and fuel?
Yes, Nylon 66 demonstrates good chemical resistance to most petroleum-based oils, greases, hydraulic fluids, and fuels. Automotive engine oil, transmission fluid, diesel fuel, kerosene, and hydraulic oil generally cause no significant degradation. However, certain aromatic hydrocarbons and aggressive solvents can swell or weaken nylon over extended exposure. Gasoline containing high aromatic content may cause slight swelling. For applications involving continuous chemical immersion, consult chemical compatibility charts specific to Nylon 66. Alternative insert materials (fluoropolymers, PEEK) provide superior chemical resistance where standard nylon is inadequate. Trojan's technical team can recommend appropriate materials for specific chemical environments.
27. Can nylon insert nuts be used in vacuum or space applications?
With specific considerations, yes. Vacuum environments pose two challenges: outgassing of volatile compounds from the nylon insert potentially contaminating sensitive equipment, and lack of atmospheric oxygen for thermal dissipation. Space-qualified fasteners typically require materials meeting NASA outgassing specifications (ASTM E595: <1.0% total mass loss, <0.1% collected volatile condensable material). Standard Nylon 66 may exceed these limits. For high-vacuum or space applications, specify vacuum-processed inserts or transition to all-metal locking nuts. Numerous spacecraft, satellites, and vacuum chambers successfully employ appropriately specified nylon insert nuts. Trojan can source space-qualified materials with appropriate certification for aerospace applications.
28. Do nylon insert nuts degrade from UV exposure?
Nylon 66 possesses inherent UV resistance superior to many polymers, but prolonged direct sunlight exposure over years causes gradual photo-oxidation. Surface embrittlement may occur, potentially reducing prevailing torque. However, since the insert resides inside the nut body, only the exposed inner surface contacts UV during storage or before installation. Once assembled, the insert is completely shielded from UV. Outdoor applications experience minimal UV degradation because the nut hex body shadows the insert. For maximum UV resistance in long-term outdoor storage, consider UV-stabilised nylon variants or store fasteners in enclosed containers. Practically, UV degradation rarely affects field performance of properly installed nylon insert nuts.

Section 5: Installation, Torque & Assembly

29. Can nylon insert nuts be installed with impact wrenches?
Not recommended for critical applications. Impact wrenches deliver high instantaneous torque through rapid hammering action, potentially damaging the nylon insert through shock loading or localised overheating from friction. The polymer insert can partially extrude, lose resilience, or develop stress cracks. For non-critical assemblies where controlled torque isn't specified, judicious use of low-power impact drivers may be acceptable - use the minimum impact power necessary and employ operator skill to avoid overtightening. Critical applications absolutely require controlled torque application using beam-type, dial-type, or electronic torque wrenches. Trojan recommends continuous-pull tightening for optimal insert life.
30. Do I need to use thread lubricant on nylon insert nuts?
Depends on the application. For most general industrial applications, no lubrication is required - the nylon insert provides sufficient anti-galling properties. However, specific circumstances warrant lubrication:

• Stainless steel applications (particularly austenitic grades prone to galling)
• High-strength fasteners with elevated installation torques
• Applications specifying precise clamp loads requiring consistent friction coefficients
• Torque-angle tightening procedures

When lubricant is used, torque specifications must be adjusted downward (typically 20-30% reduction) because lubrication reduces friction. Never apply lubricant unless assembly procedures explicitly specify it - doing so risks exceeding design clamp loads and potentially yielding threads. If specification requires lubrication, use products compatible with nylon (avoid chlorinated solvents).
31. What happens if I overtighten a nylon insert nut?
Overtightening produces several failure modes. Initially, excessive torque may extrude the nylon insert, forcing polymer material outward past the nut face or inward against the bolt threads, permanently deforming the insert and potentially reducing locking effectiveness. Continued overtightening can strip the internal threads of the nut, particularly in lower-strength materials or smaller thread sizes. Ultimate failure involves bolt tensile fracture or thread stripping. Even if catastrophic failure doesn't occur, overtightening induces residual stresses that accelerate fatigue crack initiation in cyclic loading. Always adhere to specified torque limits and use calibrated torque wrenches for critical assemblies.
32. How do I measure prevailing torque?
Prevailing torque measurement requires a calibrated torque wrench or torque meter. Two values are typically measured:
On-torque (running torque): Thread the nut onto a clean, undamaged bolt without seating it against any surface. Measure the torque required to rotate the nut continuously through the nylon insert region before the nut contacts the bearing surface. This represents pure locking torque.
Off-torque (break-away torque): After full assembly and subsequent loosening, measure the torque required to initiate nut rotation off the bearing surface. This includes both prevailing torque and any static friction from the seated joint.
Specifications establish minimum and maximum acceptable values. Trojan's quality processes include statistical sampling of prevailing torque for production lots, ensuring consistent locking performance.
33. Can nylon insert nuts be used with fine-pitch threads?
Absolutely - fine pitch threads are specifically addressed in standards BS EN ISO 7040, ISO 10511, and DIN 982. Fine pitch threads provide greater thread engagement per unit length, beneficial in thin-wall applications, hard materials, or where maximum strength is required. The nylon insert functions identically regardless of thread pitch. Fine pitch threads do require more precise manufacturing tolerances and careful handling to prevent cross-threading during installation. Trojan manufactures nylon insert nuts in coarse, fine, extra-fine, and speciality pitches across metric, Imperial, and Unified thread forms.
34. What is the minimum thread engagement length for nylon insert nuts?
Thread engagement length depends on material strength and loading conditions. For steel bolts into steel nuts, minimum engagement should equal 1.0 times the bolt diameter for Grade 8.8 materials (example: M10 requires 10mm minimum engagement). Lower-strength materials require proportionally more engagement. Since nylon insert nuts are typically taller than standard nuts, they inherently provide good thread engagement. However, ensure the bolt penetrates completely through the nylon insert region - the locking function requires thread contact with the polymer collar. Inadequate engagement reduces both strength and locking effectiveness. Trojan manufactures tall nylon insert nuts for applications requiring extended engagement.
35. Can nylon insert nuts be staked, crimped, or further secured?
Generally unnecessary and potentially detrimental. The nylon insert provides the primary locking mechanism - additional securing methods typically aren't required. Staking (punch marking the nut to deform metal into the bolt threads) or crimping risks damaging the nylon insert and may actually reduce locking effectiveness. If application requirements mandate absolutely no possibility of loosening (beyond what nylon inserts provide), consider all-metal lock nuts with post-installation crimping, castle nuts with cotter pins, or safety wiring. For extreme-vibration or safety-critical applications where redundant locking is desired, Nord-Lock washers or wedge-locking washers can supplement nylon insert nuts without interfering with the polymer insert.

Section 6: Reusability, Maintenance & Inspection

36. How many times can a nylon insert nut be reused?
No universal answer exists - reusability depends on multiple factors including insert design, material quality, installation conditions, service environment, and application severity. Laboratory testing of aerospace-grade nuts demonstrates 5-15 assembly cycles maintaining acceptable prevailing torque under ideal conditions (room temperature, clean threads, no preload between tests). Real-world service introduces additional variables: thermal cycling, chemical exposure, time-dependent creep, and invisible damage. Conservative practice limits reuse to 3-5 cycles maximum, and only for non-critical applications after prevailing torque verification. Trojan categorically recommends single-use for safety-critical applications - the modest replacement cost is insignificant compared to failure consequences.
37. How do I know if a used nylon insert nut is still good?
Several inspection criteria indicate serviceability:
Visual inspection:

• No visible nylon extrusion beyond nut face
• No discolouration, burning, or melting of polymer
• No cracks in nut hex body
• No thread damage, galling, or cross-threading
• No contamination embedded in insert

Functional testing:

• Measured prevailing torque within specification limits
• Nut threads smoothly without binding or catching
• Insert remains firmly retained in nut body

Service history:

• Known temperature exposure within limits
• Documented installation/removal cycles
• No known chemical exposure
• Reasonable service duration

If any doubt exists about nut condition, replace it. Never compromise safety for marginal cost savings.
38. What reduces the life of a nylon insert nut?
Multiple degradation mechanisms shorten service life:

• Elevated temperatures accelerating polymer aging
• Repeated installation/removal cycles causing mechanical wear
• Chemical exposure (solvents, aggressive fluids) attacking polymer
• UV radiation (outdoor storage) causing surface embrittlement
• Moisture absorption affecting dimensional stability
• Overtightening causing compressive set or insert extrusion
• Thread damage reducing locking contact area
• Contamination interfering with thread engagement
• Time-dependent creep under sustained load

Minimising these factors maximises nut life. Store fasteners in controlled environments, handle carefully during installation, and replace according to maintenance schedules rather than waiting for evident failure.
39. Can I clean and reuse nylon insert nuts removed during maintenance?
For non-critical applications, yes, provided they pass inspection criteria. Clean threads thoroughly with solvent (avoid chlorinated solvents that attack nylon - use mineral spirits or isopropanol), blow dry with compressed air, and visually inspect per previous guidelines. Measure prevailing torque on a clean bolt - if values fall within specification, cautious reuse in non-critical locations may be acceptable. However, unknowns regarding service history make this practice questionable. Many organisations maintain policies prohibiting fastener reuse regardless of apparent condition. Economic analysis often favours replacement - technician time for inspection and testing exceeds new fastener cost.
40. Do nylon insert nuts require periodic inspection or replacement schedules?
Maintenance-critical applications (aircraft, rail vehicles, elevators, pressure vessels, lifting equipment) typically mandate scheduled fastener inspection as part of preventive maintenance programmes. These schedules derive from manufacturer recommendations, regulatory requirements, operational experience, and risk assessment. Inspection may involve:

• Visual examination for damage or deterioration
• Torque verification (measurement and retightening if necessary)
• Scheduled replacement at defined intervals or utilisation cycles
• Non-destructive testing (NDT) of bolts and studs
• Documentation and traceability

Non-critical applications rarely require scheduled fastener maintenance beyond opportunistic inspection during other maintenance activities. For critical applications, consult OEM recommendations, regulatory authorities (CAA, FRA, HSE), and qualified engineering judgment to establish appropriate inspection intervals.

Section 7: Design Considerations & Engineering

41. When should I use a thin (low-profile) nylon insert nut?
Thin nylon insert nuts serve applications with restricted axial clearance where standard-height nuts cannot fit. Common scenarios include:

• Limited thread engagement length on studs or tapped holes
• Tight clearance to adjacent components
• Sheet metal assemblies where nut height matters
• Weight-reduction requirements
• Aesthetic considerations requiring low profile

Trade-offs include reduced thread engagement (lower strength) and potentially reduced locking effectiveness from shallower insert depth. Standards ISO 10512 (coarse) and ISO 10511 (fine) specify thin nut dimensions. Despite reduced height, thin nylon insert nuts still provide reliable locking for appropriate applications. Trojan manufactures thin profile nuts across comprehensive size ranges.
42. What are the advantages of nylon insert flange nuts?
Flange nuts integrate a wide washer-like bearing surface with the nut body, providing multiple benefits:

• Increased bearing area reducing surface pressure
• Elimination of separate washer (part count reduction)
• Prevention of washer loss or incorrect installation
• Better load distribution over soft materials (composites, plastics)
• Resistance to embedment into joint surfaces
• Enhanced vibration resistance from larger contact patch

Nylon insert flange nuts combine locking and load distribution in a single component, ideal for vibration-prone assemblies in soft materials. Automotive, aerospace, and consumer products extensively employ this design. Trojan manufactures serrated and non-serrated flange variants.
43. Can nylon insert nuts be used in tapped holes?
Yes, but with important limitations. When threading a nylon insert nut into a tapped hole (rather than onto a bolt), ensure adequate thread engagement depth - the hole must be deep enough to allow the nut to thread completely through the insert region plus additional engagement for strength. The through-hole must provide clearance for a wrench to install the nut. Blind tapped holes present challenges because the nut cannot bottom out, potentially leaving inadequate thread engagement. This application is relatively uncommon - typically, bolts thread into tapped holes whilst nuts go onto external threads. If your design requires nuts in tapped holes, verify sufficient depth and engagement.
44. What is the weight difference between nylon insert nuts and standard nuts?
Minimal - the nylon insert represents only 2-5% of total nut weight depending on size. For example, an M10 steel nylon insert nut weighs approximately 12-14 grams versus 12-13 grams for an equivalent plain hexagon nut. The weight increase is negligible in most applications. For extreme weight-sensitive applications (aerospace, racing, drones), consider:

• Aluminium nylon insert nuts (40-60% weight reduction versus steel)
• Thin-profile designs
• Optimised nut geometry (reduced hex body thickness where permitted)

Weight savings from material substitution dramatically exceed any difference attributable to the nylon insert itself.
45. Are left-hand thread nylon insert nuts available?
Yes. Left-hand threads (reverse helix, loosening with clockwise rotation) serve applications where conventional right-hand threads would self-loosen due to rotational direction of the assembly. Common applications include:

• Left-side bicycle pedals
• Angle grinder backing nuts
• Rotating shafts and arbours
• Certain propeller fasteners
• Mixer and blender components

Trojan manufactures left-hand nylon insert nuts across metric, Imperial, and Unified threads in standard and special sizes. The nylon insert functions identically regardless of helix direction. Left-hand nuts are typically marked with grooves or "LH" stamps to prevent installation errors.
46. Can nylon insert nuts be made in custom sizes or geometries?
Absolutely. Trojan specialises in special and non-standard fastener manufacturing. We routinely produce:

• Non-preferred thread sizes and pitches
• Oversize threads for thread repair
• Custom across-flats dimensions
• Increased or reduced nut height
• Modified insert depth or position
• Dual-thread nuts (left-hand one end, right-hand other)
• Custom materials and coatings
• Precision-tolerance variants
• Modified geometries for specialised applications

Provide drawings, specifications, or samples - our engineering team will evaluate manufacturability and recommend optimal production approaches. Minimum order quantities for custom sizes vary based on complexity but are often lower than anticipated.
47. What is the difference between a nylon insert nut and a centre-lock nut?
Centre-lock nuts employ a different locking mechanism - a crimped or deformed section in the nut body creates an out-of-round condition that binds against bolt threads. All-metal construction enables higher temperature capability (typically 300-400°C) but generally provides less consistent locking torque than nylon inserts. Centre-lock nuts are typically single-use because the metal deformation doesn't recover. Nylon insert nuts offer more reliable, quantifiable locking performance with limited reusability. Choose centre-lock all-metal nuts for high-temperature applications; choose nylon insert nuts for general applications requiring consistent prevailing torque and potential reuse.

Section 8: Quality, Testing & Specifications

48. What quality certifications do Trojan's nylon insert nuts carry?
Trojan Special Fasteners maintains comprehensive quality management systems and can provide:

• Material certificates (EN 10204 3.1 or 3.2)
• Dimensional inspection reports
• Prevailing torque test results
• Proof load test documentation
• Hardness test results
• Traceability to heat/lot numbers
• Compliance certifications to specific standards
• PPAP documentation (automotive)
• First Article Inspection Reports (FAIR) for aerospace
• RoHS and REACH declarations

Our quality processes ensure every nut meets specification requirements with full documentation supporting critical applications.
49. How is prevailing torque tested during manufacturing?
Trojan employs statistical sampling protocols testing prevailing torque on calibrated test equipment. Sample nuts from each production lot thread onto precision test mandrels (hardened, ground bolts with verified thread dimensions) mounted in torque meters. The operator rotates the nut through the insert region at controlled speed whilst the meter records running torque. Results must fall within specification limits (typically expressed as minimum and maximum values in Newton-metres). Out-of-specification results trigger investigation and potential lot rejection. This testing ensures consistent locking performance across all supplied fasteners.
50. What is proof load testing?
Proof load testing verifies nut strength by threading the nut onto a hardened mandrel and applying the specified tensile load in a calibrated testing machine. The nut must withstand this load (typically 90% of minimum thread stripping strength) for a specified duration without thread failure or permanent deformation. After load removal, the nut must still thread smoothly on a standard gauge. This destructive test is performed on samples from each production lot, verifying material strength and thread quality meet specification requirements. Proof loads are tabulated in standards for each thread size and grade.

Section 9: Comparison with Other Locking Methods

51. Are nylon insert nuts better than thread-locking adhesives?
Different approaches with distinct advantages. Nylon insert nuts provide immediate locking (no cure time), are reusable (limited cycles), require no surface preparation, work across temperature ranges from -55°C to +120°C, and function reliably in contaminated or oily environments. Thread-locking adhesives (Loctite, etc.) offer variable strength grades, higher temperature resistance (up to 230°C for high-temp formulations), complete thread engagement, and ability to seal threads against leakage. However, adhesives require clean, dry, oil-free surfaces, cure time before achieving full strength, and are essentially permanent (requiring heat for disassembly). Choose nylon insert nuts for field maintenance, rapid assembly, or reusable applications; choose adhesives for permanent assemblies or higher temperatures.
52. How do nylon insert nuts compare to distorted thread lock nuts?
All-metal distorted thread lock nuts employ deformed or out-of-round threads creating interference without polymer inserts. Advantages include extreme temperature capability (600°C+), no polymer degradation concerns, and applicability in radiation, vacuum, or chemical environments hostile to plastics. However, distorted thread nuts typically provide less consistent locking torque, may be single-use (some designs permanently deform), and cost more than nylon insert nuts. Nylon insert nuts dominate general industrial applications (temperature <120°C) due to superior performance-to-cost ratio. All-metal nuts serve high-temperature, chemical, or radiation environments where polymers cannot survive.
53. Can I use a regular lock washer instead of a nylon insert nut?
Technically yes, practically no. Extensive testing (including German Junker vibration tests) demonstrates split lock washers and spring washers provide marginal vibration resistance - they prevent loosening primarily through spring tension maintenance, which diminishes as the washer sets. Nylon insert nuts create continuous frictional interference preventing rotation even after joint relaxation. Studies show conventional lock washers often perform no better than plain washers in vibration tests. For critical applications requiring reliable anti-loosening performance, nylon insert nuts, adhesives, or positive locking methods (cotter pins, safety wire) are categorically superior. Lock washers persist mainly through historical inertia rather than engineering merit.
54. What about Nord-Lock washers versus nylon insert nuts?
Nord-Lock washers employ wedge-locking technology - pairs of washers with cam faces and radial teeth create a secure mechanical interlock. Advantages include extreme temperature capability, immunity to vibration, unlimited reusability, and no polymer degradation. They excel in structural steel, heavy equipment, and high-temperature applications. Disadvantages include higher cost (typically 5-10 times nylon insert nuts), requirement for matched pairs, and greater assembly complexity. For most general applications, nylon insert nuts provide excellent performance at lower cost. For extreme conditions (high temperature, severe vibration, critical structural joints), Nord-Lock or equivalent wedge-locking systems justify premium investment.

Section 10: Purchasing, Specification & Technical Support

55. How do I specify the correct nylon insert nut for my application?
Provide the following information to Trojan's technical team:

• Thread size and type (M10 x 1.5, 1/2"-13 UNC, etc.)
• Standard or specification (ISO 7042, MS17825, etc.)
• Material and grade (steel Grade 8, A4-70 stainless, etc.)
• Surface finish (zinc plated, passivated, galvanised, etc.)
• Nut style (standard, thin, flange)
• Special requirements (left-hand thread, oversize, etc.)
• Quantity required
• Application description (environment, temperature, criticality)
• Quality documentation needed

Our engineers will recommend optimal specifications and can suggest alternatives if your initial specification presents sourcing challenges or cost-effectiveness improvements.
56. What is the typical lead time for nylon insert nuts?
Standard sizes in common materials (steel, zinc plated or stainless) typically ship within 2-5 working days from stock. Non-standard sizes, special materials, or custom specifications typically require 4-8 weeks depending on complexity, quantity, and material availability. Large production quantities (10,000+ pieces) may require extended lead times for material procurement and production scheduling. For time-critical requirements, contact Trojan directly - we often expedite urgent orders or suggest in-stock alternatives meeting your functional requirements.
57. Do you offer technical support for fastener selection?
Absolutely. Trojan's engineering team provides complimentary application support including:

• Fastener specification and selection assistance
• Material and finish recommendations
• Torque specification guidance
• Joint design consultation
• Problem-solving for existing assemblies
• Custom design feasibility evaluation
• Standards interpretation and compliance guidance

We view technical support as integral to customer service - contact us with your application details and we'll ensure you receive optimal fastening solutions.
58. Can Trojan manufacture to obsolete or superseded standards?
Yes. We maintain extensive historical specification libraries and manufacturing knowledge for withdrawn standards including BS 1768-1, original DIN 985, ISO 7040:1983, and numerous obsolete military specifications. Maintenance operations, restoration projects, and legacy equipment support often require fasteners to discontinued standards. Provide the specification number and any available documentation - we'll determine manufacturing feasibility and quote accordingly. Our capability to produce obsolete fasteners supports customers maintaining decades-old equipment where original-specification replacement parts are otherwise unavailable.
59. Are samples available for evaluation?
Yes. Trojan can provide sample quantities for evaluation, testing, or approval purposes. For standard specifications, small sample quantities (5-50 pieces depending on size) are typically available at nominal cost. For custom specifications requiring special manufacturing, sampling may involve tooling costs and minimum production quantities. Contact our sales team with your requirements - we're committed to ensuring you receive exactly the right fasteners for your application before committing to production volumes.
60. What makes Trojan Special Fasteners different from commodity fastener suppliers?
Trojan specialises in precision manufacturing of special, non-standard, and bespoke fasteners rather than mass-produced commodity items. Our differentiators include:

• Custom manufacturing capability (size, material, geometry)
• Technical expertise supporting application engineering
• Quality documentation supporting critical industries
• UK-based manufacturing and engineering support
• Flexibility for small-batch and prototype quantities
• Legacy and obsolete specification capability
• Responsive customer service and technical consultation
• Extensive material and finish combinations

When your application demands more than off-the-shelf commodity fasteners, Trojan delivers tailored solutions with the engineering support to ensure success.

Contact Trojan Special Fasteners

For technical inquiries, quotations, or application support for nylon insert nuts and all precision fastener requirements:
Trojan Special Fasteners Ltd
Tel: 0121 789 8586
Email: trojan.fasteners@gmail.com
Web: TrojansF.co.uk
Serving UK and international customers with precision fastening solutions since [Year]. Delivering excellence in special fastener manufacturing.