Know how to calculate preload by torque

1. Thread regular tightening torque (N.m)
performance grade 5.6 performance grade 8.8 performance grade 10.9
M6 5-7 6-10 11-14
M8 12-15 19-24 22-29
M8 × 1 14-18 21-28 24-31
M10 24-30 35-47 43-53
M10 × 1.25 28-32 41-53 48-59
M10 × 1 30-36 42-54 51-58
M12 42-53 60-72 80-101
M12 × 1.5 44-56 66-82 88-107
M12 × 1.25 47-60 72-85 94-114
M14 72-87 96-126 144-175
M14 × 1.5 80-96 106-132 160-204
M16 108-127 156-200 199-234
M16 × 1.5 116-144 168-204 214-252
M18 156-180 192-226 240-260
M18 × 1.5 162-192 204-240 250-300
M20 216-243 312-372 384-439
M20 × 1.5 240-264 324-384 433-480
in addition, the tightening torque can also be calculated according to t = KDF, where k is the torque coefficient, D is the nominal diameter, and F is the bolt preload

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2. Torque = arm length × Force
2kgm = 0.5m × Force
so force = 2kgm / 0.5m = 4kg
if the preload applied on the nut is 4kg, if it is to be converted into N.m, it is not necessary to consider the nut radius of 9.8
torsion, because the nut radius has been covered by the length of the torque wrench when calculating the arm length. So just calculate the length of the torque wrench.

3. Firstly, the tightening force should be determined. For example, for M20 screws, the tightening force should be 20kg or 20 * 9.81 = 196.2n
required torque: 196.2 * 20 / 2 / 1000 = 1.962 nm
if the wrench length is 20cm, the required force is: 1.962 / 20 * 100 = 9.81 nm, i.e. 1kg
determine the tightening torque according to the wrench length, wrench length: l (m),
tightening force: F (n)
tightening torque: m (nm); The formula is as follows: M = LF

4. Bolt pre tightening force is the pre tightening force along the axis of bolt generated between bolt and connected parts under the action of tightening torque in the process of tightening bolt. For a specific bolt, the pre tightening force is related to the tightening torque of the bolt, the friction between the bolt and the nut, and the friction between the nut and the connected part. Pre tightening torque MT = k × P0 × d × 0

5. The tightening torque of spanner and the pre tightening force can be calculated by using the friction resistance formula of screw pair in mechanical principle. If the tightening torque is too large, the strength will be adversely affected, and if it is too small, the reliability of the connection can not be guaranteed, The tightening torque or pre tightening force must be controlled. As for the anti loosening measures after tightening, it is also necessary knowledge for a designer

6. Thread regular tightening torque (N.m)
performance grade 5.6 performance grade 8.8 performance grade 10.9
M6 5-7 6-10 11-14
M8 12-15 19-24 22-29
M8 × 1 14-18 21-28 24-31
M10 24-30 35-47 43-53
M10 × 1.25 28-32 41-53 48-59
M10 × 1 30-36 42-54 51-58
M12 42-53 60-72 80-101
M12 × 1.5 44-56 66-82 88-107
M12 × 1.25 47-60 72-85 94-114
M14 72-87 96-126 144-175
M14 × 1.5 80-96 106-132 160-204
M16 108-127 156-200 199-234
M16 × 1.5 116-144 168-204 214-252
M18 156-180 192-226 240-260
M18 × 1.5 162-192 204-240 250-300
M20 216-243 312-372 384-439
M20 × 1.5 240-264 324-384 433-480
in addition, the tightening torque can be calculated according to t = KDF, where k is the torque coefficient, D is the nominal diameter, and F is the bolt preload

7. The calculation formula is: tightening torque = torque coefficient × Preload × Nominal diameter of thread
the key is the torque coefficient. With the same thread specification, the torque coefficient of different surface treatment is different, and some even differ by one time. Therefore, it is not appropriate to calculate the torque according to 0.12 in some manuals or standards. The torque coefficient shall be obtained by test.

8. 2012-5-3 8:55:05 screw tightening torque only rely on theoretical calculation is not enough, in practical application, screw connection tightening torque is mainly to meet the proct in the work, transportation fastening and anti loosening. The inspection of screw fastening and anti loosening is usually verified by vibration test. Vibration test can be determined according to different procts and relevant national reliability and environmental test standards. To sum up, the determination of the appropriate screw tightening torque should be based on the "reference value of screw tightening torque" in the table, assemble a batch of procts, and then observe whether the screw is screwed in place, whether there is thread slippage and damage, and whether the screw is broken; At the same time, according to the proct standard vibration test, screw connection can not be loose. Through wall bolt through wall screw special shaped nut high strength nut anchor bolt standard parts steel die clamp fishtail plate fishtail bolt passage splint

9. The tightening torque of spanner and the pre tightening force can be calculated by using the formula of friction resistance of screw pair in mechanical principle. If the tightening torque is too large, it will have an adverse impact on the strength, and if it is too small, it can not guarantee the reliability of the connection. Therefore, for important bolt connection, tightening torque or preload must be controlled. As for the anti loosening measures after tightening, it is also necessary knowledge for a designer.

10. According to the formula above, it reaches 1500nm, which is obviously too large. According to the formula I know, it is even larger, reaching 1800nm. Regardless of the above load, it is calculated directly according to the conventional calculation, and 1000nm is enough!