F.A.Q. self locking nuts
Q: What is the locking torque of a stainless steel joining lock nut?
the torque depends on the material class of the self locking nut
| Standard threads | Quality class | tightening | tension in the bolt | locking torque Nm | ||
| torque | kN | 1st deturn | 5th deturn | |||
| in Nm | MIN (µ = 0,20) | MAX (µ = 0,12) | MIN | MIN | ||
| M3x0,5 | A2 or A4-70 | 1,06 | 1,13 | 1,81 | 0,15 | 0,50 |
| A2 or A4-80 | 1,36 | 1,5 | 2,41 | |||
| M4x0,7 | A2 or A4-70 | 2,31 | 1,97 | 3,16 | 0,20 | 0,70 |
| A2 or A4-80 | 3,01 | 2,63 | 4,21 | |||
| M5x0,8 | A2 or A4-70 | 4,43 | 3,19 | 5,11 | 0,30 | 1,50 |
| A2 or A4-80 | 5,81 | 4,26 | 6,81 | |||
| M6x1 | A2 or A4-70 | 7,6 | 4,52 | 7,23 | 0,40 | 1,70 |
| A2 or A4-80 | 10 | 6,03 | 9,64 | |||
| M8x1,25 | A2 or A4-70 | 17,6 | 8,23 | 13,17 | 0,60 | 2,80 |
| A2 or A4-80 | 23,6 | 10,98 | 17,56 | |||
| M10x1,5 | A2 or A4-70 | 35,1 | 13,05 | 20,88 | 1,10 | 3,30 |
| A2 or A4-80 | 46,6 | 17,4 | 27,84 | |||
| M12x1,75 | A2 or A4-70 | 60,9 | 18,96 | 30,34 | 1,90 | 4,00 |
| A2 or A4-80 | 79,9 | 25,29 | 40,46 | |||
| M14x2 | A2 or A4-70 | 95,5 | 25,88 | 41,4 | 2,50 | 5,50 |
| A2 or A4-80 | 126,5 | 34,5 | 55,2 | |||
| M16x2 | A2 or A4-70 | 147,5 | 35,33 | 56,52 | 3,50 | 7,70 |
| A2 or A4-80 | 195,5 | 47,1 | 75,36 | |||
| M18x2,5 | A2 or A4-70 | 204 | 43,2 | 69,12 | 6,00 | 10,00 |
| A2 or A4-80 | 270 | 57,6 | 92,16 | |||
| M20x2,5 | A2 or A4-70 | 286,5 | 55,13 | 88,2 | 8,50 | 14,50 |
| A2 or A4-80 | 379,5 | 73,5 | 117,6 | |||
| µ = 0,20 corresponds with 50% Re of the bolt |
| µ = 0,12 corresponds with 80% Re of the bolt |
| this is the norm NFE25-035 |
Q: Why use a joining lock nut to fasten compressor valves?
Your advantages to switch over to a joining lock nut:
1) Single piece joining lock nut that does not require specific knowledge or multiple tools for installation
2) A locking fastener with prevailing torque that functions completely independent of any preload
3) 50% quicker installation
4) Consistent prevailing torque enabling exact bolt tensions to be achieved with each installation
5) Reduce inventory (single piece instead of two pieces) eliminating of mix-ups when matching top and bottoms
6) No galling and consistent friction coefficients for stainless steel utilizing a unique, permanent tin based anti-galling treatment
stainless steel A4 anti-galling joining lock nuts installed on compressor valves
Q: WHAT TORQUES ARE APPLIED ON THESE NUTS WHEN USED ON VALVES?
The locking torque for class 8 material locking nuts can be find in this table, they are according to the norm DIN EN ISO 2320
| Standard threads | tightening | Locking torque in N.m | ||
| torque | 1st turn | 1st deturn | 5th deturn | |
| in kN | MAX | MIN | MIN | |
| M3x0,5 | 2,2 | 0,43 | 0,12 | 0,08 |
| M4x0,7 | 3,8 | 0,90 | 0,18 | 0,12 |
| M5x0,8 | 6,2 | 1,60 | 0,29 | 0,20 |
| M6x1 | 8,7 | 3,00 | 0,45 | 0,30 |
| M8x1,25 | 15,9 | 6,00 | 0,85 | 0,60 |
| M10x1,5 | 25,3 | 10,50 | 1,50 | 1,00 |
| M12x1,75 | 36,7 | 15,50 | 2,30 | 1,60 |
| M14x2 | 50 | 24,00 | 3,30 | 2,30 |
| M16x2 | 68,2 | 32,00 | 4,50 | 3,00 |
| M18x2,5 | 86,2 | 42,00 | 6,00 | 4,20 |
| M20x2,5 | 110 | 54,00 | 7,50 | 5,30 |
| M22x2,5 | 136 | 68,00 | 9,50 | 6,50 |
| M24x3 | 159 | 80,00 | 11,50 | 8,00 |
| M27x3 | 206 | 94,00 | 13,50 | 10,00 |
| M30x3,5 | 253 | 108,00 | 16,00 | 12,00 |
| Fine Threads | tightening | Locking torque in N.m | ||
| torque | 1st turn | 1st deturn | 5th deturn | |
| in kN | MAX | MIN | MIN | |
| M8x1 | 17 | 6,00 | 0,85 | 0,60 |
| M10x1 | 28,1 | 10,50 | 1,50 | 1,00 |
| M10x1,25 | 26,6 | 10,50 | 1,50 | 1,00 |
| M12x1,25 | 41 | 15,50 | 2,30 | 1,60 |
| M12x1,50 | 38,3 | 15,50 | 2,30 | 1,60 |
| M14x1,50 | 54,4 | 24,00 | 3,30 | 2,30 |
| M16x1,5 | 72,7 | 32,00 | 4,50 | 3,00 |
| M18x1,5 | 97,5 | 42,00 | 6,00 | 4,20 |
| M20x1,5 | 122 | 54,00 | 7,50 | 5,30 |
| M22x1,5 | 150 | 68,00 | 9,50 | 6,50 |
| M24x2 | 173 | 80,00 | 11,50 | 8,00 |
| M27x2 | 224 | 94,00 | 13,50 | 10,00 |
| M30x2 | 280 | 108,00 | 16,00 | 12,00 |
