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south bend 9"A threading

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  • south bend 9"A threading

    I need to cut a 10TPI on a piece of steel approximately 1/2" in diameter. I set the quick change gear box to the A position and the second lever to the third position under the 10's column. I ended up with 5 TPI. What am I doing wrong. I have not cut threads before. Thanks for any help in advance Fred

  • #2
    Did you have the 20 tooth stud gear in place?

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    • #3
      Originally posted by laddy
      I need to cut a 10TPI on a piece of steel approximately 1/2" in diameter. I set the quick change gear box to the A position and the second lever to the third position under the 10's column. I ended up with 5 TPI. What am I doing wrong. I have not cut threads before. Thanks for any help in advance Fred
      I have no experiance with that lathe. But if You set the lever under the 20's column I would think ya might end up with 10tpi. based on what You cut already.

      It sounds like the QC is running to fast in relation to the chart ie wrong input gear?

      Steve

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      • #4
        Hey,
        Thanks for the help. What's with the 20 tooth stud gear? Should my lever be in a different position? I have no additional gears to pop in. Appreciate your help Fred

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        • #5
          Hopefully these pics will help you out.
          This is 10tpi on my 9A. Compare your stud gear setup to mine.
          The 40 tooth gear is currently unused and stored on the bottom stud in the picture.
          Steve

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          • #6
            take a picture of the gear train ...and lable the gears with the teeth count

            post and

            then the guys here can tell you whats what.

            all the best.markj

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            • #7
              Yikes,
              My secondary gear in that position is 1.22" in diameter and 7 TPI now where near as big as your secondary gear. Imguess I will have to go shopping! Thanks to all for the help Fred

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              • #8
                Originally posted by laddy
                Yikes,
                My secondary gear in that position is 1.22" in diameter and 7 TPI now where near as big as your secondary gear. Imguess I will have to go shopping! Thanks to all for the help Fred

                It might still be worth your while to post a picture of your setup, it may be that some rearranging of what you have could work.
                --
                Tom C
                ... nice weather eh?

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                • #9
                  What do you mean, "7 TPI"?

                  I suspect you have the gears you need, they are just arranged incorrectly.

                  In any case, it sounds as though, with the setup you have, if you set the levers for 20 tpi you'll get 10 tpi.

                  Pick up a copy of South Bend's "How to Run a Lathe" book from Lindsay Publications, or elsewhere. It will explain all this. There's a PDF version floating around on the Internet -- anybody have a link to it?
                  ----------
                  Try to make a living, not a killing. -- Utah Phillips
                  Don't believe everything you know. -- Bumper sticker
                  Everybody is ignorant, only on different subjects. -- Will Rogers
                  There are lots of people who mistake their imagination for their memory. - Josh Billings
                  Law of Logical Argument - Anything is possible if you don't know what you are talking about.
                  Don't own anything you have to feed or paint. - Hood River Blackie

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                  • #10
                    Thanks to All! I was looking at the wrong gear! Many thanks for all the help. You guys are great! Fred

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                    • #11
                      The only thing that matters is the first (stud) gear*, and the last, the input shaft gear.

                      Those must have a certain relation. Anything else in single gears in between is irrelevant.

                      You can figure this out. To do an 8 TPI thread, the spindle and the 8 TPI leadscrew (IIRC that's what you have) must turn the same speed.

                      So set the box to 8 TPI, and turn the input shaft. Count turns of input per turn of lead screw.

                      The result is the number of turns you must have on the input shaft per spindle turn to get the 8 TPI. Put in gears to do that

                      All the other settings will follow (unless stated otherwise in your table)

                      * Actually, if the stud gear is not 1:1 with the spindle, you need to take that into account in your ratio
                      1601

                      Keep eye on ball.
                      Hashim Khan

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                      • #12
                        "The only thing that matters is the first gear, and the last gear.
                        Those must have a certain relation. Anything else in single gears in between is irrelevant."

                        Those are important words worth reading again.

                        This applies to a gear train.
                        If you stack two gears and continue with that stacked gear, then you are starting a new train, and another ratio change.

                        --Doozer
                        Last edited by Doozer; 11-22-2009, 10:36 PM.
                        DZER

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                        • #13
                          Hey,
                          Made the switch and it works fine. Many thanks to everybody! Mike and Steve you came to my rescue. My how to run a lathe bok said nothing. I really appreciate everybodys aid. I couldn't post a pic because my kid is in college and no one to help this old geezer through the photobucket maze. Happy Thanksgiving to all Fred

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                          • #14
                            Glad the pics helped you out!

                            Steve

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