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Thread: Torquing prop bolts

  1. #1

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    Torquing prop bolts

    What’s the consensus on getting accurate torque reading on prop bolts?
    I've been told that lube will give a false (over torque) reading.
    My experience with dry (no lube), the bolts start “creaking” when getting tight making it difficult to get an accurate reading.
    Some recommend parafin wax (?)
    whats the correct procedure?
    Thanks for your input,
    Doug.

  2. #2
    www.SkupTech.com mike mcs repair's Avatar
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    Read the instructions. No oil most likely


    Sent from my iPhone using SuperCub.Org

  3. #3
    wireweinie's Avatar
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    What Mike said. Standard hardware torques are usually dry. If lube is required, installation instructions will say so and indicate the correct lube to use.

    Web
    Life's tough . . . wear a cup.

  4. #4
    PerryB's Avatar
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    I like to clean the lugs with a brass rifle bore brush using a low speed drill, and a brass toothbrush on the bolt threads. This gets them shiny clean without any thread wear, and I've never had any creaking or sticking. They draw down quite smooth when dry this way.
    After Monday and Tuesday, even the calendar says WTF !
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    Catto mentions parafin wax, but also uses Belleville washers for install.
    McCauley, to my knowledge, makes no mention of thread treatment prior to prop install.
    My small block Chevy build manual suggests lube with “light oil” on torqued bolts.
    Is there no standard recommendation that would allow us all to arrive at a common value when torquing a bolt? Especially a prop bolt?
    Last edited by Oliver; 08-20-2018 at 11:24 PM.

  6. #6
    PerryB's Avatar
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    Quote Originally Posted by Oliver View Post
    Catto mentions parafin wax, but also uses Belleville washers for install.
    McCauley, to my knowledge, makes no mention of thread treatment prior to prop install.
    My small block Chevy build manual suggests lube with “light oil” on torqued bolts.
    Is there no standard recommendation that would allow us all to arrive at a common value when torquing a bolt? Especially a prop bolt?
    I think the parafin wax is for the lugs so they slip into the the counter-bores easier, and if they're using Belleville's that's something new since I got mine. When I bought my Catto they didn't even provide bolts or a crush plate. Those had to be sourced from Saber mfg. Of course none of this was disclosed until AFTER I had my prop. They build a wonderful prop, but I've never been impressed with how the front end of that place is run. -- Sorry, venting....
    After Monday and Tuesday, even the calendar says WTF !

  7. #7
    wireweinie's Avatar
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    Or . . . you could read the instructions from the manufacturer.

    McCauley for instance, has different requirements for different installations. Some installations use dry torque, some use oil on the threads, and some require grease. Just do a search for service bulletin SB227B. It calls for 'light oil' for some and Mil-T-83483 grease for others. Also a big warning to never use dry torques when a lube is called out OR lubed torques when dry is called out.

    There is no one way to torque all prop bolts.

    Web
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  8. #8
    Steve Pierce's Avatar
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    Never see the belville washers on the Catto. I always start the prop bolts by hand, snug with a speed handle and then torque and had no issues.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  9. #9

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    Spent a little time in the hangar today fooling around with a torque wrench and prop bolts.
    As per sb227b (thanks Web) clean and dry threads on Lycoming.
    With a very accurate and calibrated (Snap On) digital torque wrench, discovered that friction between dry washers, bolt head and spinner mounting plate can produce significant friction and false readings
    lubticating washer surfaces eliminates bolt “creaking” also minimizes galling and crushing alum spinner mount.

    That is my consensus on getting accurate prop bolt torque and my 2c for what it’s worth.
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  10. #10
    Steve Pierce's Avatar
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    Were you using the Piper washers or AN washers? Interesting to know that the noise is from the washers.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  11. #11
    hotrod180's Avatar
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    Quote Originally Posted by wireweinie View Post
    …..McCauley for instance, has different requirements for different installations. Some installations use dry torque, some use oil on the threads, and some require grease. Just do a search for service bulletin SB227B. It calls for 'light oil' for some and Mil-T-83483 grease for others.....
    Both my Cessna 100 series service manual and my McCauley C200/400 series operators manual call out for "clean and dry threads",
    as does the paperwork that came along with the STC to install this prop.
    But when I got my C201 back from overhaul, the prop shop supplied me a little tube of milspec grease and explicit instruction for lubing the nuts & studs before torquing.
    I still have some of the grease left, but unfortunately now I can't find those darn instructions.

    EDIT: Thanks for posting the link to that SB , Web.
    Think I'll print it out and put it with my prop STC info.
    It indicates that torque instructions are on a sticker on the prop itself, which I kinda recall now.
    Last edited by hotrod180; 08-27-2018 at 11:23 AM.
    Cessna Skywagon-- accept no substitute!
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  12. #12

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    Quote Originally Posted by Steve Pierce View Post
    Were you using the Piper washers or AN washers? Interesting to know that the noise is from the washers.
    Using hardware provided from Dominion with Borer prop.
    bolts, AN970 and AN960 washers with bolts.

    Catto provides 24 belville washers and 6 AN960’s with their crush plate hardware kit.
    maybe a recent thing,
    torquing with belville washers (4 per bolt) is where I had the biggest issue with erratic readings from creaking bolts, assumed it was threads in the bolts/prop hub but not the case.

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