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Thread: Left hand thread ?

  1. #1
    alan speyrer is offline Hot Rolled
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    Default Left hand thread ?

    Hey guys, i am needing to cut a left hand 7/16"-20tpi with my south bend 10k lathe. I have cut right hand threads many times, never left hand threads, so i am asking what is the proper way to cut left hand threads on a south bend lathe. I have a threading dial.
    when i cut right hand threads i like to cut from the chuck to the tailstock with the lathe in reverse. So i would like to cut left hand threads the same way if possible.

    thanks

  2. #2
    davycrocket's Avatar
    davycrocket is offline Hot Rolled
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    Default L/H thread

    Alan
    The only reason that your lathe was in reverse was so that you COULD cut from chuck towards Tailstock, presumably with the tool in a rear toolpost .(Or upside down in the front toolpost)
    So to cut a L/H thread start from the chuck but with the lathe spindle in forward direction and the tool in the front toolpost . .

    Davycrocket
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  3. #3
    alan speyrer is offline Hot Rolled
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    If the lathe spindle is in the forward direction, then it should cut threads from the tailstock toward the chuck. I dont understand.

    Quote Originally Posted by davycrocket View Post
    Alan
    The only reason that your lathe was in reverse was so that you COULD cut from chuck towards Tailstock, presumably with the tool in a rear toolpost .(Or upside down in the front toolpost)
    So to cut a L/H thread start from the chuck but with the lathe spindle in forward direction and the tool in the front toolpost . .

    Davycrocket

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    davycrocket's Avatar
    davycrocket is offline Hot Rolled
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    Alan
    Doesn't your lathe have reverse/ tumbler gears to allow you to make the leadscrew turn in either direction regardless of the direction of turning of the main spindle ?
    This is what they look like on my lathe . Leadscrew rotation is reversed using the lever with the round black Knob ( Not the spindle lock knob towards the top/rear of the spindle )!!

    Just checked on lathes

    On your lathe it's the lever sticking out where the end cover joins the headstock. You should be able to put the leadscrew into forward , neutral or reverse
    Davycrocket
    Attached Thumbnails Attached Thumbnails tumbler-gears.jpg   southbend-10k-medium-.jpg  

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    alan speyrer is offline Hot Rolled
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    your correct

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    Cool

    Quote Originally Posted by alan speyrer View Post
    when i cut right hand threads i like to cut from the chuck to the tailstock with the lathe in reverse. So i would like to cut left hand threads the same way if possible.

    thanks
    The lathe spindle will be turning forward as normal operation. The lead screw will be turning toward the tailstock (bottom hole on the for/rev lever). The compound will be swiveled with the handle toward the chuck at 29.5 degrees and cut away. The carriage will be in (netrual center hole) Use the half nut lever to cut. Just watch your fingers if moving close to the chuck...Bob
    Bob Wright Metal Master Fab
    Salem, Ohio Birthplace of the Silver and Deming Drill, all others are copies.

  7. #7
    kitno455 is offline Titanium
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    Except it's acme, so 15 degrees or so.

    allan

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    mcruff is offline Stainless
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    Default

    Quote Originally Posted by kitno455 View Post
    Except it's acme, so 15 degrees or so.

    allan
    How do you know, or are you just guessing?

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    Cool

    Quote Originally Posted by mcruff View Post
    How do you know, or are you just guessing?
    He must have some inside info LOL...Bob
    Bob Wright Metal Master Fab
    Salem, Ohio Birthplace of the Silver and Deming Drill, all others are copies.

  10. #10
    kitno455 is offline Titanium
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    No, just guessing

    allan

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