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Thread: Frictional Coefficient for nylock nuts

  1. #1
    Associate Engineer
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    Frictional Coefficient for nylock nuts

    I have been trying to find something that tells me the frictional coefficient for nylock nuts. When I calculate the torque values using nylock nuts I don't have a frictional coefficient. Is there something out there, or will I need do some experiments to determine this?

    Thanks

  2. #2
    Administrator Kelly Bramble's Avatar
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    Quote Originally Posted by gfzeigler View Post
    I have been trying to find something that tells me the frictional coefficient for nylock nuts. When I calculate the torque values using nylock nuts I don't have a frictional coefficient. Is there something out there, or will I need do some experiments to determine this?

    Thanks
    Experiments are typically are done to obtain an average frictional torque. However, for critical torque applications the frictional torque is determined at installation of each individual fastener and then summed to get the final torque.

    For example:

    Design torque = 20 in-lbs
    Actual frictional measured torque = 3 inch-lbs
    Applied torque = 23 in-lbs

  3. #3
    Technical Fellow
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    There will be a bunch of stuff associated with the frictional torque dependent on bold diameter, probably nut height (not sure if it differs with half-height nuts) and application temperature. Nylon is very susceptible to temperature so you will also need to throw that into the works. I know of no reliable data sheets on the topic, so it will probably come down to test and see.

    However, having said that, if locking and torque load is that critical, you may be better off looking at an all metal lock-nut approach instead. Much more reliable and stable, but a few pennies more. You do not see Nylocs on the end caps of connecting rods.

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