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Thread: Threaded Insert or Not

  1. #1
    Associate Engineer
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    Threaded Insert or Not

    I have a 6" X.75" cylindrical part with a 1.5" flange and -20 threads that will support 250 Lb. A ratchet tool will rotate this part vertical on a steel threaded rod stock (ASTM A193 Grade B7 >130,000 psi) used as a stud. I went with the fine threads for fine adjustment. This is part of a bigger assembly that has fixtures for assembly and caster wheels for transporting.

    The question is what is better and most cost effective:

    1. Use a threaded insert or
    2. Use a steel material which will be taped.




    If using a steel material is better, what is a good steel that is cheap and easy to find that wont have a problem.
    I always had the philosophy that threaded inserts were a burden and a simpler solution is to design the screw size and engagement or material instead of the extra step of adding a insert. For example, Im a big bike rider and in the bike industry most of the parts are aluminum with no insert, the screw size is upsized and the torque spec is low with some aluminum fasteners used in some areas.

    In my case, I can use steel because I am not concerned about weight as long as it is low cost and easy to find. If it is easier for the machinist, I would switch the part to aluminum with a helical insert.

    Thanks for your input.

  2. #2
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    Welcome to the group, but, you have not supplied enough information to form practical suggestions.

    There are also conflicts that will add to the confusion. Fine threads in aluminum is not a good idea, especially so if this thing is going up and down frequently.

    How frequently will it be going up and down?

    Will the threads be regularly lubed or set and forget?

    Steel type? Whatever is best suited to the application and at this point we are left guessing.

    A single "stud" may not be the best option but a picture would be worth 784 more words.

  3. #3
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    One option is to use aluminum and a insert if the alluminum part less expensive than steel.

    I might be used once a day, lubed and forget.

    Yes, I'm wondering, if steel, what kind can you directly tap and have good threads. So what is a cheap steel that you can easily machine.untitled_zpsc59d13e1.jpg

    ]

  4. #4
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    For steel, 12L14 is a high lead-content easy-machining steel, but with any steel the easier to machine the lower the strength.

    Why so concerned about cost? Steel is cheap and in fact, without checking first, my guess would be that 12L14 is probably more expensive (pennies) than simple old 1018. As I said, choose a steel that is best suited to the application. Easy of tapping would be a minute issue unless there are 30,000 to be tapped.

  5. #5
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    Thanks, I like the 12L14 option. What does the lead do? Is it better for threads? Any health issues?


    I was looking for a low cost option because I wanted a go-to solution that was simple and low cost. Shops run out of threaded inserts and install them wrong, that I thought that eliminating the threaded insert would be a good idea.

    I looked at cost of the material required for that part that you suggested and they are a lot lower than I thought. The aluminum is a lot cheaper that I thought.


    For 1.5" X 12" Rod:

    6061-T6 -$17.90
    12L14 -$13.67
    1018 - $14.70

  6. #6
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    Quote Originally Posted by Killroy View Post
    Any health issues?
    Well, that depends, the answer is much like the stupid Lead-Law the people who care for us Legislated for motorcycle batteries on motorcycles. If you are sucking on the battery terminal then it is probably gonna be bad for your health after a few years of that.

  7. #7
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    Quote Originally Posted by PinkertonD View Post
    Welcome to the group, but, you have not supplied enough information to form practical suggestions.

    There are also conflicts that will add to the confusion. Fine threads in aluminum is not a good idea, especially so if this thing is going up and down frequently.

    How frequently will it be going up and down?

    Will the threads be regularly lubed or set and forget?

    Steel type? Whatever is best suited to the application and at this point we are left guessing.

    A single "stud" may not be the best option but a picture would be worth 784 more words.

    I refuse to count, but I am guessing you did. This made me groan loud enough that my manager stepped out of his office! I groaned, but deep down, I think it was genius!

  8. #8
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    Quote Originally Posted by Lumpidydumpy View Post
    I refuse to count, but I am guessing you did.
    Thanks, but guilty -- it was a guess. Although, 784 seemed a random enough number of about the correct order to be believable.

    My deepest apologies for forcing the groan and the Manager's expended effort to rise from his throne-of-power to investigate.

  9. #9
    Administrator Kelly Bramble's Avatar
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    Details pending, untanged threaded inserts like Keenserts are easily removable/replace-able. Regardless of material one could replace the inserts should wear be an issue.

  10. #10
    Lead Engineer RWOLFEJR's Avatar
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    Ball screws and nuts are pretty inexpensive if you want to make it really slick and easy to operate? The ball nut would outlive a regular nut by 1,214,895 cycles... Give or take... Probably get a nut and a foot of screw for under $200.oo... ?

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