What is the size of bolt (thread size, not head size) and how long is the thread engagement?
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Errors in manuals do happen! The secondary clutch is spec'd at 4.6 ft*lbs. in one of my manuals, when it should be 46 ft*lbs.
In general, the rule of thumb to ensure that the bolt breaks before the threads strip is 1x bolt diameter thread engagement for steel, and 1.5x bolt diameter thread engagement for aluminum minimum, though this depends a bit on the alloy of the threads, and gauge of the bolt.
If you're working on something where the torque spec isn't available, there are charts for the general specs for a given bolt diameter and strength, like the example below. In general, your aiming to achieve a clamp load of 75%-90% of the bolts yield strength, using the torque (friction) to measure it. That friction is heavily dependent on thread condition; most manuals spec the torque clean and dry by default and will specify lubrication if required. It's also not that consistent, with a given torque producing a typical variance in clamp load of around +-10%.
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In general, the rule of thumb to ensure that the bolt breaks before the threads strip is 1x bolt diameter thread engagement for steel, and 1.5x bolt diameter thread engagement for aluminum minimum, though this depends a bit on the alloy of the threads, and gauge of the bolt.
If you're working on something where the torque spec isn't available, there are charts for the general specs for a given bolt diameter and strength, like the example below. In general, your aiming to achieve a clamp load of 75%-90% of the bolts yield strength, using the torque (friction) to measure it. That friction is heavily dependent on thread condition; most manuals spec the torque clean and dry by default and will specify lubrication if required. It's also not that consistent, with a given torque producing a typical variance in clamp load of around +-10%.
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