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  • Threading issue

    My SB9 does not have a QC gearbox and one cannot set one up the this model SB9 so I need to manually change gears to accomplish any threading.
    This is a pic of the gears, are they correct for threading.


    I attempted a few times, unsuccessfully, and would be grateful for any help with this. I thought I followed the sequence to properly make threads but it didn't work although it looked like a few threads did appear momentarily and then back to just turning.
    thanks,

  • #2
    The most likely cause it not using the thread dial correctly. If the dial slips or you miss the mark on a subsequent pass, the result is a coarsely turned surface instead of threads.

    As far as the gears go, if you selected the correct set and they stayed engaged, there's not much that can go wrong there.
    Any products mentioned in my posts have been endorsed by their manufacturer.

    Comment


    • #3
      Good question "are they correct for threading"? They are as shown in the photo BUT
      for what TPI? Nobody knows unless you count the gears the stud gear and the lead
      screw gear so a gear chart is a must they are online. In short take a light cut and
      measure that if the pitch gauge says 10, thats the gears in there. If you have a thread
      dial with lathe off Manually turn it by pulley or belt engauge 1/2 nut (stop) now mesh
      the thread dial just pick a number your choice and lock the dial. start machine and try
      it using the same mark every time. If you do not have a dial put a piece of tape some
      where on the lead screw and count it. Oh there are those who leave half nut on and
      reverse machine, personally I dont like that. That just puts more wear on the 1/2 nut.
      best I can explain. If you have a pitch gauge and complete set of change gears-good
      ta go.

      Comment


      • #4
        Originally posted by big job View Post
        Good question "are they correct for threading"? They are as shown in the photo BUT
        for what TPI? Nobody knows unless you count the gears the stud gear and the lead
        screw gear so a gear chart is a must they are online. In short take a light cut and
        measure that if the pitch gauge says 10, thats the gears in there. If you have a thread
        dial with lathe off Manually turn it by pulley or belt engauge 1/2 nut (stop) now mesh
        the thread dial just pick a number your choice and lock the dial. start machine and try
        it using the same mark every time. If you do not have a dial put a piece of tape some
        where on the lead screw and count it. Oh there are those who leave half nut on and
        reverse machine, personally I dont like that. That just puts more wear on the 1/2 nut.
        best I can explain. If you have a pitch gauge and complete set of change gears-good
        ta go.
        Yes, the thread dial is set on "1" as it is engaged when the threading is started, but still not working correctly.

        Comment


        • #5
          You are currently setup with the dual compounds for fine feed. That cuts something like 480 TPI. You need the gear change chart:

          http://www.lathes.co.uk/southbend9-inch/img19.gif

          allan

          Comment


          • #6
            I think what the others are trying to tell you is this: there isn't any quick way to tell you what the lathe is set for now, wrt to tpi (other than doing a dry run.) Using the threading dial is relatively simple and the markings (number to watch) will change with different tpi. Normally, the dial will rotate until you engage the lever on the apron. Your job is to engage that lever when the right number lines up with the index mark. You also need the chart for selecting change gear combinations.
            gvasale

            Comment


            • #7
              Originally posted by gvasale View Post
              I think what the others are trying to tell you is this: there isn't any quick way to tell you what the lathe is set for now, wrt to tpi...
              Actually, there is: 8 TPI / (16/54*18/72*18/80) = 480 TPI. See how easy that was? (sarcasm)

              allan

              Comment


              • #8
                If you don't have a set of change gears and the appropriate chart you are unable to set up for the pitch of the thread you are attempting to cut. You either need to know how to do the math to set up the gears (the hard way) or use a chart. I suggest you obtain a copy of South Bends, How to Run a Lathe. It's a great little reference and inexpensive. Available on Ebay usually.

                Comment


                • #9
                  Originally posted by big job View Post
                  Oh there are those who leave half nut on and
                  reverse machine, personally I dont like that. That just puts more wear on the 1/2 nut.
                  best I can explain. If you have a pitch gauge and complete set of change gears-good
                  ta go.
                  You can thread day and night like that and I'm sure that either Darwin or pension comes first before the nuts fail.
                  Amount of experience is in direct proportion to the value of broken equipment.

                  Comment


                  • #10
                    Allen I wasn't planning on counting teeth on all those gears to figure it out. When I deal with change gears, I do it only because its necessary. I don't even remember what I have the feed set for on my Atlas 10F.
                    gvasale

                    Comment


                    • #11
                      Apparently you missed the 'sarcasm' part

                      I happen to have the SB 9" change gear choices memorized. Strange, considering I don't even own one. But it comes in handy on the SB forum over at PM.

                      allan

                      Comment


                      • #12
                        I don't run a Southbend, but it's pretty obvious to me that every gear meshing here is a reduction, so I see no reason to disagree with Allan - you're cutting a thread that's so fine you'll need to use a sewing needle for your tool to realise you're not just turning.

                        There's something about the gearchange charts that's not clicking with you.

                        Start from here: if the lead screw turns at the same rpm as the spindle - ie the gearing is one to one - you'll cut a thread that has the same TPI as the leadscrew. If the leadscrew turns at half spindle speed, you'll get a thread that's twice as fine.
                        Richard - SW London, UK, EU.

                        Comment


                        • #13
                          Originally posted by kitno455 View Post
                          You are currently setup with the dual compounds for fine feed. That cuts something like 480 TPI. You need the gear change chart:

                          http://www.lathes.co.uk/southbend9-inch/img19.gif

                          allan


                          Dead right Allan.

                          Unless or until the OP comes to grips with and tries and masters your posted gear change chart he will continue to have a problem.

                          Once he has it right and has the correct gears correctly set up he should be set to go screw threading.

                          Perhaps someone can post a list of the gears for that lathe so that he can see what if any gears are missing - and do someting about getting new "missing" ones.
                          Last edited by oldtiffie; 11-09-2012, 07:00 PM.

                          Comment


                          • #14
                            Allan: I didn't miss the sarcasm. I like sarcasm. Sometimes is the best thing. I didn't grow up as a machinist, and I still have a lot to learn and always have time to read the book. But I still couldn't make a stab at that photo and come up with any more than a guess. So, you may be a couple of steps ahead of me and it doesn't bother me a bit.
                            gvasale

                            Comment


                            • #15
                              Originally posted by oldtiffie View Post


                              Dead right Allan.

                              Unless or until the OP comes to grips with and tries and masters your posted gear change chart he will continue to have a problem.

                              Once he has it right and has the correct gears correctly set up he should be set to go screw threading.

                              Perhaps someone can post a list of the gears for that lathe so that he can see what if any gears are missing - and do someting about getting new "missing" ones.
                              The extra gears that came with the lathe are;60T-56T-54T-52T-43T **the others are 46-44-40-32-24.
                              How many constitute a whole set for this lathe?
                              thanks for helping with this.

                              Comment

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