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Which is stronger?

Discussion in 'The Hokey Ass Message Board' started by Waddayacare, Aug 1, 2012.

  1. Okay, I need my memory refreshed! These things happen when you get older.

    Which is stronger when taping into steel, fine thread or course?

    Course tells me it will bite deeper but fine tells me more threads per.
     
  2. damagedduck
    Joined: Jun 16, 2011
    Posts: 2,341

    damagedduck
    Member
    from Greeley Co

    fine,more contact material
     
  3. fine like said above.
     
  4. Hey thanks guys!

    I owe you one!
     

  5. TagMan
    Joined: Dec 12, 2002
    Posts: 6,294

    TagMan
    ALLIANCE MEMBER

    Unless of course you're putting threads into aluminum, then you need the depth of course threads.
     
  6. i agree with that ^
     
  7. belyea_david
    Joined: Sep 21, 2010
    Posts: 134

    belyea_david
    Member
    from Regina, SK

  8. Fine, but fine thread is for something that is not going to be taken apart very often.
     
  9. Nope!

    Only plan on putting it together for mock-up, break it down for paint, then reassemble (hopefully once). :D

    Thanks Beaner!
     
  10. The37Kid
    Joined: Apr 30, 2004
    Posts: 30,629

    The37Kid
    Member

    I think a stud in aluminum would have a longer life than a bolt, depending on what the envolved parts are. Bob :)
     
  11. firingorder1
    Joined: Dec 15, 2006
    Posts: 2,147

    firingorder1
    Member

  12. VoodooTwin
    Joined: Jul 13, 2011
    Posts: 3,453

    VoodooTwin
    Member
    from Noo Yawk

    Here is some info to consider;

    Coarse Threads:
    Coarse threads are commonly used where rapid assembly or disassembly is required.
    If corrosion or damage from handling or use is likely.
    They allow for easier starting with less cross threading.
    In relatively low strength materials such as cast iron, aluminum, magnesium, brass, bronze, and plastic, coarse threads provide more resistance to stripping than fine or extra fine threads.
    If subjected to heat, they are less likely to seize than fine threads.

    Fine Threads:
    Fine threads are commonly used for nuts and bolts in high strength applications.
    While applications vary, in general, fine threads are approximately 10% stronger than coarse threads.
    They have less of a tendency to loosen under vibration because the smaller lead or thread helix angle provides better wedging action when the assembly is tightened.
    Fine threads are also used for fine adjustment and thin walled applications due to the shallower thread height.
    Fine threads are generally easier to tap. Since the thread height is shallower, the chip load per tooth and chip volume are lower, resulting in less tapping torque and breakage, particularly in difficult to machine materials.
    Less chip volume also means that more lubrication will reach the cutting teeth resulting in longer tap life.
    Fine threads require larger tap drill than for coarse threads, which improves the performance of the drill and tap
     
  13. Damn!

    This is some valuable information. I never gave it much thought about vibration, and I will be dealing with that. I have already tapped the holes to fine thread and now that I read this I'm glad I did.

    Thanks V.D.T.!
     
  14. Thunder should have all fine thread in the frame and all nuts and bolt units and all nuts. There's probably some course threaded holes in the aluminum, if it takes a stud, the nut will be fine if a bolt then it will be that thread. Some of the aluminum has steel inserts that are fine threaded
     
  15. B.schmidt
    Joined: Jun 1, 2012
    Posts: 13

    B.schmidt
    Member
    from Kansas

    Fine threads are stronger, 1.5 times the diameter of tap, for actual thread depth is what a machinist handbook would call out for minimum thread depth. Thats why most high quality pullers are hardened fine threads.
     

  16. Pullers use fine threads for mechanical advantage.
     
  17. hotrod40coupe
    Joined: Apr 8, 2007
    Posts: 2,561

    hotrod40coupe
    Member

    I usually like to put a steel insert in aluminum for added strength.
     
  18. Ha Ha!

    It's not for Thunder. :cool:
     
  19. metlmunchr
    Joined: Jan 16, 2010
    Posts: 861

    metlmunchr
    Member

    Its near impossible to pull a thread out of steel, coarse or fine, before the pulling force breaks the bolt itself, so long as the female thread is of sufficient depth.

    The primary reason a fine thread bolt is stronger than a coarse one made of the same material is that the fine one has a bigger diameter at the root of the thread. IOW, there's more area to break on the fine versus the coarse, so the load is spread over a larger area.

    The real advantage to fine threads is their increased resistance to loosening under vibration. That's why you see so many fine thread fasteners used in aircraft. Strength of coarse vs fine shouldn't ever be used as the main criteria in deciding whether to use one fastener or the other, because, if the joint is critical, that small difference in strength isn't enough to assure safety and the fastener needs to be larger.
     

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