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Nylock jam nuts — also called nylon insert jam nuts or prevailing torque thin nuts — are low-profile hex nuts with a nylon collar bonded into the top of the nut that deforms around the bolt thread on installation. That interference creates a prevailing torque that resists loosening under vibration and dynamic loading, without any secondary locking device. Compared to a standard nylock nut, the jam nut version sits roughly 40–50% lower in profile, making it the preferred choice in assemblies where axial space is restricted.
These fasteners are manufactured to DIN 985 and ISO 7042 standards in metric thread profiles, and are available in stainless steel (SS 304, SS 316), carbon steel (Grade 6, Grade 8), and alloy steel. Industries that rely on them include automotive & off-highway equipment, HVAC and mechanical ventilation systems, electrical enclosure fabrication, and general structural engineering — wherever bolt joints face sustained vibration or require a tamper-evident locking mechanism.
| Parameter | Details |
|---|---|
| Material Variants | Stainless Steel (SS 304, SS 316), Carbon Steel (Grade 4, 8), Alloy Steel |
| Grade Options | A2-70, A4-80, ASTM A194 Gr. 2H, Gr. 8 |
| Size Range | M3 to M36 / 1/8" to 1-1/2" |
| Thread Type | Metric (Coarse/Fine), UNC, UNF |
| Standards | DIN 985 (modified), ISO 7040, ASTM A194, BS EN ISO |
| Surface Finish | Plain, Zinc Plated, Hot Dip Galvanized, PTFE Coated |
| Type Variants | Hex Jam Nylock Nuts, Thin Nylon Insert Lock Nuts |
| Hardness | Carbon Steel: 24–36 HRC, Stainless Steel: As per ASTM specs |
| Tensile Strength | Up to 800 MPa (depending on grade) |
| Thread size d | M5 | M6 | M7 | M8 | M10 | M12 | M14 | M16 | M18 | M20 | M22 | M24 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| - | - | - | M8x1 | M10x1 | M12x1,5 | M14x1,5 | M16x1,5 | M18x2 | M20x2 | M22x2 | M24x2 | ||
| - | - | - | - | M10x1,25 | M12x1,25 | - | - | M18x1,5 | M20x2 | M22x2 | - | ||
| P | 0,8 | 1 | 1 | 1,25 | 1,5 | 1,75 | 2 | 2 | 2,5 | 2,5 | 2,5 | 3 | |
| da | min. | 5 | 6 | 7 | 8 | 10 | 12 | 14 | 16 | 18 | 20 | 22 | 24 |
| max. | 5,75 | 6,75 | 7,75 | 8,75 | 10,8 | 13 | 15,1 | 17,3 | 19,5 | 21,6 | 23,7 | 25,9 | |
| dw | min. | 6,9 | 8,9 | 9,6 | 11,6 | 15,6 | 17,4 | 20,5 | 22,5 | 24,9 | 27,7 | 29,5 | 33,2 |
| e | min. | 8,79 | 11,05 | 12,12 | 14,38 | 18,9 | 21,1 | 24,49 | 26,75 | 29,56 | 32,95 | 35,03 | 29,55 |
| h | max. = nominal size | 6,3 | 8 | 8,5 | 9,5 | 11,5 | 14 | 16 | 18 | 20 | 22 | 25 | 28 |
| min. | 6 | 7,7 | 8,2 | 9,14 | 11,14 | 13,64 | 15,3 | 17,3 | 19,16 | 20,7 | 23,7 | 26,7 | |
| m | min. | 4,4 | 4,9 | 6,14 | 6,44 | 8,04 | 10,37 | 12,1 | 14,1 | 15,1 | 16,9 | 18,1 | 20,2 |
| m´ | min. | 3,52 | 3,92 | 4,91 | 5,15 | 6,43 | 8,3 | 9,68 | 11,28 | 12,08 | 13,52 | 14,48 | 16,16 |
| s | max. = nominal size | 8 | 10 | 11 | 13 | 17 | 19 | 22 | 24 | 27 | 30 | 32 | 36 |
| min. | 7,78 | 9,78 | 10,73 | 12,73 | 16,73 | 19,67 | 21,67 | 23,67 | 26,16 | 29,16 | 31 | 35 | |
| Weight (7,85 kg/dm3) kg/1000pcs | 1,4 | 3,1 | 3,2 | 6 | 11,7 | 16,6 | 21 | 37,8 | 51,6 | 68 | 86 | 127 | |
| Thread d | M3 | M4 | M5 | M6 | M7 | M8 | M10 | M12 | M14 | M16 | M18 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| - | - | - | - | - | M8x1 | M10x1 | M12x1,5 | M14x1,5 | M16x1,5 | M18x2 | ||
| - | - | - | - | - | - | M10x1,25 | M12x1,25 | - | - | M18x1,5 | ||
| P | 0,5 | 0,7 | 0,8 | 1 | 1 | 1,25 | 1,5 | 1,75 | 2 | 2 | 2,5 | |
| da | min. | 3 | 4 | 5 | 6 | 7 | 8 | 10 | 12 | 14 | 16 | 18 |
| max. | 3,45 | 4,6 | 5,75 | 6,75 | 7,75 | 8,75 | 10,8 | 13 | 15,1 | 17,3 | 19,5 | |
| dw | min. | 4,6 | 5,9 | 6,9 | 8,9 | 9,6 | 11,6 | 15,6 | 17,4 | 20,5 | 22,5 | 24,9 |
| e | min. | 6,01 | 7,66 | 8,79 | 11,05 | 12,12 | 14,38 | 18,9 | 21,1 | 24,49 | 26,75 | 29,56 |
| h | nominal= max. | 4 | 5 | 5 | 6 | 7,5 | 8 | 10 | 12 | 14 | 16 | 18,5 |
| min. | 3,7 | 4,7 | 4,7 | 5,7 | 7,14 | 7,64 | 9,64 | 11,57 | 13,3 | 15,3 | 17,66 | |
| m | min. | 2,4 | 2,9 | 3,2 | 4 | 4,7 | 5,5 | 6,5 | 8 | 9,5 | 10,5 | 13 |
| m´ | min. | 1,65 | 2,2 | 2,75 | 3,3 | 3,85 | 4,4 | 5,5 | 6,6 | 7,7 | 8,8 | 9,9 |
| s | nominal= max. | 5,5 | 7 | 8 | 10 | 11 | 13 | 17 | 19 | 22 | 24 | 27 |
| min. | 5,32 | 6,78 | 7,78 | 9,78 | 10,73 | 12,73 | 16,73 | 18,67 | 21,67 | 23,67 | 26,16 | |
| Weight (7,85Kg/dm3) kg/1000pcs | 0,5 | 1 | 1,4 | 2,4 | 3 | 5,1 | 10,6 | 17,2 | 26 | 34 | 45 | |
| Thread d | M20 | M22 | M24 | M27 | M30 | M33 | M36 | M39 | M42 | M45 | M48 | |
| M20x2 | M22x2 | M24x2 | M27x2 | M30x2 | M33x2 | M36x3 | M39x3 | M42x3 | M45x3 | M48x3 | ||
| M20x1,5 | M22x1,5 | - | - | - | - | - | - | - | - | - | ||
| P | 2,5 | 2,5 | 3 | 3 | 3,5 | 3,5 | 4 | 4 | 4,5 | 4,5 | 5 | |
| da | min. | 20 | 22 | 24 | 27 | 30 | 33 | 36 | 39 | 42 | 45 | 48 |
| max. | 21,6 | 23,7 | 25,9 | 29,1 | 32,4 | 35,6 | 38,9 | 42,1 | 45,4 | 48,6 | 51,8 | |
| dw | min. | 27,7 | 29,5 | 33,2 | 38 | 42,7 | 46,6 | 51,1 | 55,9 | 60,6 | 64,7 | 69,4 |
| e | min. | 32,95 | 35,03 | 39,55 | 45,2 | 50,85 | 55,37 | 60,79 | 66,44 | 72,09 | 76,95 | 82,6 |
| h | nominal= max. | 20 | 22 | 24 | 27 | 30 | 33 | 36 | 39 | 42 | 45 | 48 |
| min. | 18,7 | 20,7 | 22,7 | 25,7 | 28,7 | 31,4 | 34,4 | 37,4 | 40,4 | 43,4 | 46,4 | |
| m | min. | 14 | 15 | 15 | 17 | 19 | 22 | 25 | 27 | 29 | 32 | 36 |
| m´ | min. | 11 | 12,2 | 13,2 | 14,8 | 16,5 | 18,2 | 19,8 | 21,5 | 23,1 | 24,8 | 26,5 |
| s | nominal= max. | 30 | 32 | 36 | 41 | 46 | 50 | 55 | 60 | 65 | 70 | 75 |
| min. | 29,16 | 31 | 35 | 40 | 45 | 46 | 53,8 | 58,8 | 63,8 | 68,1 | 73,1 | |
| Weight (7,85Kg/dm3) kg/1000pcs | 65 | 75 | 100 | 162 | 212 | 317 | 415 | 499 | 628 | 771 | 998 | |
Nylock Jam Nuts are used to secure threaded assemblies where vibration resistance and space-saving design are critical.
Nylock Jam Nuts are typically produced through cold forging followed by precision threading and insertion of the nylon locking element. This process ensures high dimensional accuracy and consistent mechanical properties across batches. Post-manufacturing, each lot undergoes inspection including thread gauge verification, hardness testing, and torque performance checks.
KK Fasteners follows structured quality control protocols aligned with ISO 9001 standards, including batch traceability and material certification. Surface finish and coating thickness are also verified to ensure compliance with international specifications such as ASTM and DIN.
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Nylock Jam Nuts are low-profile locking nuts with a nylon insert that creates friction against the bolt threads. This prevents loosening under vibration or dynamic loads. They are widely used in compact assemblies where space is limited but secure fastening is critical.
They are manufactured in stainless steel grades such as SS 304 and SS 316, carbon steel, and alloy steel. Stainless steel is preferred for corrosion resistance in marine and outdoor environments, while carbon steel is used for high-strength and cost-sensitive industrial applications.
Nylock Jam Nuts are commonly produced as per DIN 985 (modified for jam nut profile), ISO 7040, and ASTM A194 standards. These ensure dimensional accuracy, torque performance, and compatibility with international fastening systems.
Selection depends on application conditions such as vibration level, load requirement, and environment. SS 316 is ideal for corrosive or marine conditions, while carbon steel grades are better suited for structural and heavy-duty mechanical assemblies.
A reliable supplier should offer material traceability, ISO-certified production, and compliance with international standards. Consistent quality inspection and export experience are key factors. KK Fasteners supplies Nylock Jam Nuts with documented quality control and global delivery support.
Nylock Jam Nuts provide a compact, reliable solution for vibration-resistant fastening across diverse industrial applications. With controlled manufacturing processes and consistent quality checks, KK Fasteners supports global buyers with dependable supply and technical support. For detailed specifications or bulk inquiries, request a quote or connect with the engineering team to discuss your exact requirements.
