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A question about bolts

Discussion in 'The Garage' started by ugly_blazer, Sep 6, 2004.

  1. ugly_blazer

    ugly_blazer 1/2 ton status

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    If I had two bolts that were the same size, only was one fine thread and one coarse thread, and using a torque wrench I applied the same amount of torque to each bolt would the clamping force of the bolts be the same or would one be more?
     
  2. BranndonC

    BranndonC 3/4 ton status

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    /forums/images/graemlins/thinking.gif using that philosophy, would the aging of the torque wrench have an effect on the over all exactness of said wrench, there for yielding an erroneous outcome?
     
  3. ugly_blazer

    ugly_blazer 1/2 ton status

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    Anything is possible. /forums/images/graemlins/thumb.gif

    I was just wondering, because if fine thread bolts clamp tighter I may use then to attach some stuff that I don't want to move (fall off).
     
  4. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I think that the clamping load would be exactly the same.

    You'd be shocked how much clamping load a bolt can create though.

    Why not just use larger bolts?
     
  5. ugly_blazer

    ugly_blazer 1/2 ton status

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    [ QUOTE ]
    Why not just use larger bolts?

    [/ QUOTE ]

    It's not a lot of fun drilling holes larger than 1/2" in my frame. I'm probably being overcautious, but it would be embarrassing if I went to pull someone and my bumper fell off.
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    1/2" is what I had in mind. A 1/2" bolt will provide a tremendous amount of clamping force. I can't imagine you needing more clamping force than a 1/2" bolt is capable of providing.

    1/2" bolts are holding my trailer hitch and 5th wheel hitch in my tow rig just nicely. /forums/images/graemlins/thumb.gif
     
  7. ugly_blazer

    ugly_blazer 1/2 ton status

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    Ya, I guess you're right. I have never had a hitch break off that was using 1/2" bolts.
     
  8. tbill

    tbill Registered Member

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    Use a Grade 5 or better bolt and there will be no problems.
     
  9. SkulzNBonz

    SkulzNBonz 1/2 ton status

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    The surface area of the load would be different, I think. It seems that area the load would be spread across (# of threads) is larger in a fine thread as opposed to a coarse thread. With this in mind, the accuracy of the torque reading would be greater? /forums/images/graemlins/dunno.gif Most torque wrenches are calibrated within about 3% of actual, so I don't how much of a difference that would make. If you don't want a bolt to come loose, use Loc Tite or Nyloc nuts. Most places you find fine thread bolts are on mechanisms that require a tight fit with very little tolerance. Engineering gurus, is this accurate?

    John
     
  10. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

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    dunno about "clamping force", but fine threads = more surface area and therefore more friction...

    j
     
  11. surpip

    surpip 1 ton status

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    on the jet we dont often use ny-lock's or loc-tite, we use nust that have been made out of round and those donr coem off, even on a crazy shakin jet on the 'cat. /forums/images/graemlins/waytogo.gif
     
  12. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I personally prefer prevailing torque style lock nuts.
     
  13. 86chevybanshee

    86chevybanshee 1/2 ton status

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    not to hi jack or anything, but i heard something about grade 5 bolts are better than grade 8's because the g5's bend and the g8' break, is this true?
     
  14. darkshadow

    darkshadow 1 ton status

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    1/2 bolt flat washer lock washer lock nut, your all set.
    if your really really really really worryed, find some grade 9 airospace bolts. would hate to think of the cost though /forums/images/graemlins/ignore.gif
     
  15. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

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    [ QUOTE ]
    not to hi jack or anything, but i heard something about grade 5 bolts are better than grade 8's because the g5's bend and the g8' break, is this true?

    [/ QUOTE ]

    no.

    j
     
  16. SkulzNBonz

    SkulzNBonz 1/2 ton status

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    [ QUOTE ]
    not to hi jack or anything, but i heard something about grade 5 bolts are better than grade 8's because the g5's bend and the g8' break, is this true?

    [/ QUOTE ]
    No, because yet though a grade 5 may be more mallible (bendable) it still has less tensile strength than a grade 8, and will therefore fail sooner (i.e. with less of a load) than a grade 8.

    John
     
  17. 84gmcjimmy

    84gmcjimmy 1 ton status

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    [ QUOTE ]
    not to hi jack or anything, but i heard something about grade 5 bolts are better than grade 8's because the g5's bend and the g8' break, is this true?

    [/ QUOTE ]

    I forget where I heard/read this, but someone said that if you use grade5 bolts in the right place, they can be better than grade8's... the example is for a snowplow, you;d rather bend a bolt, that can still limp the plow home, than to have a grade 8 break, and leave the plow there...
     
  18. diesel4me

    diesel4me 1 ton status Premium Member

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    This may be true--I have broken a few grade 5 and 8 bolts on my plow(the pins that hold the plow to the plow frame)and all I could get at that late hour was cheap grade 2 bolts at home depot--I hit a few obsructions during the duration of the storm,and I thought sure the bolts would snap(they were 3/4 inch x 6 inch)but the next day I checked them--they looked like banannas,but they didnt crack or break!I know stainless steel bolts are not good for a lot of automotive applications,they dont rust but they seem to be brittle,and dont like heavy shock loads,I tried stainless steel studs in my exhaust manifolds once thinking I;d never have to change them again--WRONG! the next time I went to loosen them,they snapped off like peanut brittle,I had to pull the manifold and have them removed at a machine shop with an end mill--none of my drills would even scratch them /forums/images/graemlins/angryfire.gif. I use cheap carriage bolts or threaded rod for exhaust studs now--they wont be useable again anyway,gaurenteed to break off,but at least they drill out easy. I also put a new front suspension crossmember in a friends corvair,he pirated all stainless bolts from his workplace,we snapped 3 of them just tourqing them into place--we decided they werent the hot setup for shock mounts and suspension bolts,and ended up buying grade 8 bolts from the hardware store.I have noticed that grade 5 and 8 bolts corrode much slower that the cheap grade 2 stuff--maybe better coatings on them,or just better steel?. /forums/images/graemlins/crazy.gif
     
  19. Triaged

    Triaged 1/2 ton status

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    A fine thread and a corse thread bolt of the same size, material, plating, and lubrication will provide the same ammount of clamping force with the same torque.

    What you are missing is that a fine thread bolt can be torqued to a higher rating then a corse thread bolt (all else being the same). The higher torque is what will give it more clamping force.

    The same is true for grade 5 vs grade 8 (FWIW SAE grade 9 doesn't exist!). Because a grade 8 is made from a stronger material it can be torqued to a higher value then a grade 5 bolt. This will give the grade 8 more clamping force.
     
  20. ugly_blazer

    ugly_blazer 1/2 ton status

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    Ok, thanks. I have always wondered how that worked, thinking that maybe a fine thread would be like a lower gear ratio, more power from less work. Guess not, thanks.
     

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