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Back Spindle Spider

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  #1  
Unread 07-24-2013, 06:40 PM
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Back Spindle Spider

Thinking to add spider to my lathe, so I'm planning on building one from 4140. The back spindle is threaded, its metric thread 1.5 the OD is 1400. So I'm thinking to bore out hole for ID thread so I can screw it on the spindle and add setscrews to hold it in place. Well if anyone done this before I'm open to any suggestions...
Here is picture of the back spindle with one nut removed to expose threads.

Thank you ;-)

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  •   #2  
    Unread 07-24-2013, 09:00 PM
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    Re: Back Spindle Spider

    Plain ol' cold roll will work just fine, no need for chrome moly, here.
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      #3  
    Unread 07-24-2013, 11:03 PM
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    Re: Back Spindle Spider

    Then I got 2" OD piece of rusted 1020 just for this
    And I made quick sketch what I think I'm going to make... Without CNC and them can-cycles it will be a challenge to get that ID thread...




    change of plans... this would make threading less complex






    Last edited by Jinx-); 07-25-2013 at 12:09 AM. Reason: cut-view & EC
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      #4  
    Unread 07-26-2013, 03:29 PM
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    Re: Back Spindle Spider

    odd thread it is, looks like m39x1.5, I think its extended metric thread... still working on it
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      #5  
    Unread 07-26-2013, 04:03 PM
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    Re: Back Spindle Spider

    The pitch isn't hard to figure, as long as you have a metric pitch gauge. The O.D.,,,,,, well, you can (and should) mic it, then convert to metric. It's not like you can thread this spider part way, remove it from the chuck and try it 'till it fits. So, you have the jam nut from the spindle. I'd use the jam nut as a gauge and make a threaded stub, 'till the nut fit right. I'd use that threaded stub as a gauge while making the spider. Basic manual machining that it didn't take a program to figure out. A mark on the threading bar for depth will tell you when to dis-engage the split nut. 'Canned cycles" are nice, but, not needed for every job.
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      #6  
    Unread 07-26-2013, 04:06 PM
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    Re: Back Spindle Spider

    I can't disengage half-nut for metric threads.... have to stop then reverse...
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      #7  
    Unread 07-26-2013, 04:15 PM
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    Re: Back Spindle Spider

    I would make it as compact as you could to reduce any out of balance the spider could bring. shoulder it out on the spindle as well so the set screw is not taking the brunt of the pressure and just needs to act as a fail safe. Clock it with your front chuck, makes life easier.

    Use a dial indicator on the carriage to stop dead on the same number each time, set it to touch at 0 then disengage at 0+ one rev, puts you nuts on each time.
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