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  • Help with threading needed WARNING large pics

    I'm home, still nurseing a broken ankle. I thought it might be a good time to spend 2 or 3 months trying to figure why I can't thread on the SouthBend 9.

    Can someone with a SB9 tell me if this looks like their drive setup?


    This is my chart on the machine and when I follow its instructions and then put in a threaded rod it don't come close tracking properly (is that even possible?) The threaded rod I used was a chunk of 1/2" by 13 tpi.


    I was using the rocker style SouthBend threading tool but am going to the type that I can use in the tool block as I know it's more steady. My rocker is homemade and not nearly useable. What do I want to waste, the red or the yellow? Note the red has some backangle introduced. I have a pink wheel I can dress this on. The blank is cobalt.



    I am setup on 29 1/2 near as I can tell. The compound angles off to the right. I am assuming this is right as I face the lathe.


    All of my previous attempts were with the lantern tool holder and now I'm thinking some of my ratty looking threads had to do with unstable tool rest.

    As mentioned earlier, putting a section of threaded rod into the 3jaw and setting the bit properly in the thread I noticed that it would not track properly. Was that even a valid test?

    Any help is appreciated. I have several books on the subject and still haven't worked it out. Im convinced the secret to lifes riches, at least for me, lays in learning to thread. Am I destined to die a pauper? Thanks in advance.
    Last edited by Your Old Dog; 10-01-2006, 06:45 PM.
    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    Thank you to our families of soldiers, many of whom have given so much more then the rest of us for the Freedom we enjoy.

    It is true, there is nothing free about freedom, don't be so quick to give it away.

  • #2
    YOD, Either HSM or MW had a good article on threading a few months ago and it focused on the SB. Worth looking up if you can.

    By not tracking, do you mean not giving the pitch you expect? Check the gears driving the leadscrew, back to the tumbler reverse gears. OOPS, that's probably the info you want !

    Found it ... here you go: http://www.lathes.co.uk/southbend9-inch/page6.html

    It looks like you're set up like figure 2 in the gear chart.

    I think your compound is angled the wrong way. As you advance the compound, you want the left edge of the tool to advance into the left wall of the thread being cut. The right edge should just skim the right hand wall of the thread being cut, due to the 29.5 degree compound angle.

    For a final cleanup pass, the cross slide can be advance a slight amount so that the tool cuts BOTH walls at the same time, giving the final profile.

    Den
    Last edited by nheng; 10-01-2006, 06:55 PM.

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    • #3
      My head hurts I read thru that site but I'm hoping maybe someone with a SB9, take Evan for instance, would maybe mount up on that big white steed with shineing armour and come romping down the forum lane to confirm that my gear train looks right or I got something switched !! I think theres several guys on this site with SB's. Thanks for the effort, I scratch you down in the "favors owed" booklet I keep !!

      Ray.........
      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      Thank you to our families of soldiers, many of whom have given so much more then the rest of us for the Freedom we enjoy.

      It is true, there is nothing free about freedom, don't be so quick to give it away.

      Comment


      • #4
        All looks ok to me .Just grind the top of the tool down to center of the center I my self would go to the yellow line. dont see why it wont work .Unless you got wore out half nuts . and i would not thank so looking at condition of lathe. hope this helps. Set your compound the other way it should read 60 not 30 as in picture. that is the problem . OLD LANE
        Last edited by lane; 10-01-2006, 07:03 PM.
        Every Mans Work Is A Portrait of Him Self
        http://sites.google.com/site/machinistsite/TWO-BUDDIES
        http://s178.photobucket.com/user/lan...?sort=3&page=1

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        • #5
          Ok, hold your head with your left hand and give us a tooth count on the large gear to the left. Also, what's the tooth count on the driven gear to the right, mounted on the leadscrew? The numbers should be stamped on the gears somewhere but the photos don't show it. Looking for 80, 72 or something like that.

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          • #6
            NO your gears are RIGHT.
            Every Mans Work Is A Portrait of Him Self
            http://sites.google.com/site/machinistsite/TWO-BUDDIES
            http://s178.photobucket.com/user/lan...?sort=3&page=1

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            • #7
              Counted the left one at 80. Right one at 56. The stud gear looks wrong. I'm counting 20 teeth. Its the outer gear on the shaft that's driving the largest gear. From the chart, for threading it should be 16, 24 or 32.

              At this point, I'll step aside for other SB comments

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              • #8
                YOD do you have a thread dial on your machine? Placing a hunk of all thread in the chuck and hoping it lines up is a long shot. The best way is to place a piece of 1/2 HR in the chuck and cut a relief about a 2" in or so move your carriage back a about 1" or so from the end using the thread dial and engage the carriage and thread to the relief... Withdraw tool reverse the carriage back before the stock. Advance your cut in and engage the carriage when the mark comes around again. The lead in will take-up and play in the nut and if you miss the mark you can reset. Also put the lathe in back gear to slow things down.
                Wow... where did the time go. I could of swore I was only out there for an hour.

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                • #9
                  Thanks for the interest in this problem.

                  I will count up all the gears tomorrow and label them. I do have a thread dial on this machine and I don't think it's my problem. I'll also post a shot of one of my past attempts to thread to show you how ratty it is. It may offer a clue as to whats wrong.

                  I was concerned that mounting a section of 1/2 x 13tpi threaded rod in the lathe, closing the half nut and then positioning the bit in the thread using the cross and compound slides and the machine would not trach properly when turned by hand. It makes me think there is a problem with the gearing.

                  I'll get more infor for you all tomorrow.

                  Thanks again,
                  Ray...........
                  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                  Thank you to our families of soldiers, many of whom have given so much more then the rest of us for the Freedom we enjoy.

                  It is true, there is nothing free about freedom, don't be so quick to give it away.

                  Comment


                  • #10
                    Your gearing looks correct to me. The stud gear (the one that engages with the tumbler reverse gears) should be 20 teeth. The screw gear (the one that goes into the QC box) should be 56 teeth. The number of teeth on any intervening idler gears don't matter.

                    To cut the top row on the threading chart (4, 4 1/2, 5, etc.) you change the 20T stud gear for the 40T gear that's stored beside the 56T gear.
                    ----------
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                    Don't believe everything you know. -- Bumper sticker
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                    There are lots of people who mistake their imagination for their memory. - Josh Billings
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                    • #11
                      I'll have to look it up ( minds like a sieve at times ) but depending on odd or even pitch you engage the thread dial on different marks. Doing otherwise will make for something that looks like a rat chewed on it
                      Wow... where did the time go. I could of swore I was only out there for an hour.

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                      • #12
                        YOD & SGW, Sorry, my mistake on the stud gear. The 1939 "How to Run a Lathe" book did not show the stud gear for QC machines (too old) and I grabbed the non-QC chart. Been on the road all afternoon and should just READ only Den

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                        • #13
                          I have a model C, so no quick change gear box for me. I have threaded on my lathe. You NEED a threading gauge, you know so you engage the half nuts at the correct time. Your tool needs to be 60 degrees, can use one of those fish tail gauges to grind to. the 29.5 is half of 60 plus a little allowance. You cut only one side of the thread, plus a little bit more each pass by feeding in the compound until you have a full thread. Really amazing the first time you do it as you see an actual thread starting to develope.

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                          • #14
                            YOD, the easiest way to find out if it is threading the same pitch as you have the tumblers set on is with a dial indicator. Mount an indicator parallel to the movement of the saddle and engage the half nut. Then make a mark on your chuck and headstock with a pen so you can see when you have turned the chuck one complete turn. Make sure to turn it a couple of times to get out any slack out of the gear train. Now zero the indicator and measure exactly how much the saddle moves per one revolution of the chuck. This will tell you exactly the how much the saddle is moving per rev. Multiply this movement by the number of threads you are trying to cut and it should equal one inch. Now compare it to what you have the gear box set to. If it is not right then you definitely have a problem in the gear train. Example: if you set the gear box to thread 10 threads per inch, the saddle should advance exactly .100 per turn of the spindle. If you multiply 10 times .100 then you will get 1 which represents one inch. Make sure and turn the chuck in the same direction all of the time to prevent getting any slack in your measurements.
                            Jonathan P.

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                            • #15
                              Threading on a lathe

                              Hi YOD,

                              I can cut threads on my lathe,(not a SB) and some are rough looking. I just buff them on the buffer wheel and they work fine.

                              I normally only cut threads that are above 1/2", on the lathe. I use a die for 1/2" and under. The threads look better.

                              Just my 2 cents.

                              Good luck on your threading.
                              skeeter

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