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  • Internal threads

    I had to cut some internal threads 1" 10tpi, so I ground a tool and cut the threads and the unit works fine. Tonight I have read 2 pieces that say cutting from right to left ( outside to inside ) set the compound to the left looking down at the lathe. I did it wrong but it came out ok. WHY? Can anyone tell me?
    thanks
    ed

  • #2
    being a newb like me you probably took it slow. also your lathe may be fairly tight. it makes the most difference in a loose lathe and heavy cuts. at least thats my interpretation of what i have read and experienced.

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    • #3
      Look at the link

      http://www.metalartspress.com/PDFs/6...ee_threads.pdf
      Non, je ne regrette rien.

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      • #4
        That is one of the sites I was looking at. My question is still the same. I did it the exact reverse of the diagram and still don't understand why my threads came out ok.
        ed

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        • #5
          It makes no difference which direction you cut the threads. It is easier for some to cut internal threads fron the headstock toward the tailstock. It reduces the worry of disengaging the halfnuts blind.

          The purpose of angling the compound is twofold. It reduces cutting forces by cutting only on one flank of the thread. It also supposedly produces a better thread form, although I question this. If, as you should, you make a final spring pass or two without advancing the compound, the thread will turn out the same regardless of the compound angle.

          With heavier lathes and/or fine threads, there is little real need to angle the compound.
          Last edited by JCHannum; 03-16-2009, 08:18 PM.
          Jim H.

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          • #6
            Originally posted by gr8life
            That is one of the sites I was looking at. My question is still the same. I did it the exact reverse of the diagram and still don't understand why my threads came out ok.
            ed
            You were removing metal from the right face of thread rather than the more conventional left face of the thread - the thread width grows toward the right instead of the left. Other than being more vulnerable to slop in the compound and half-nuts, it works the same.

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            • #7
              Thanks, I think I get it.
              ed

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