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  • Lathe half nut

    Isent the lathe half nut/threading dial a rather inconvient system?

    a 1 dog (or some kinda of keyed/indexable clutch) system connected directly to the spindle would work much better.

    IE: just allow the spindle to rotate entire revolutions and only clutch it to the lead screw when it aligns up to whatever point it was unclutched from.

    If im thinking right here, would'nt it allways produce correct engagement points even for metric threads on an imperial leadscrew?
    I mean, if you rotate something 1 exact turn.. reguardless of its pitch (or indeed, number of threads), your right back where you started. Hence if you rotate any number of exact turns, your right back where you started..

    The only downside I can see is you have to keep the leadscrew half nut engaged, and move the leadscrew to go back for a second pass...

    But on the plus side, im pertty sure it should be possable to electronicaly (motor) rotate the leadscrew with the clutch disengaged, then reengage to the correct point anywhere.. since its 'indexed' to the rotation of the spindle, and not the leadscrew anymore. Or just reverse the lathe.. Plus side here is you don't have to *stop* the lathe to stop the thread feed on a dime, even with oddball threads, and you get an engagement point *every* revolution of the spindle, insted of having to wait for some thread dial to line up every 1/8~2"
    (and having to swap gears in the thread dial if your doing metric!)
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

  • #2
    You mean like a Hardinge HLV?

    Or this conversion for a mini lathe?

    http://www.gadgetbuilder.com/Dog_Clutch.html
    Paul Compton
    www.morini-mania.co.uk
    http://www.youtube.com/user/EVguru

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    • #3
      so why isent it seen more?
      Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

      Comment


      • #4
        Basically a dog clutch never knows how far along the shaft it is it may be in the right place to drive but numbers of revs out of sync.

        peter
        I have tools I don't know how to use!!

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        • #5
          Isn't that what the half nuts do? Don't they engage the lead screw at the point you released them if you just look at the number on the thread dial? What is so hard about watching the number on the thread dial and engaging the halfnuts?

          I don't thread over 120 rpm on my lathe and have no trouble catching the right number. If I were threading at 300 rpm or more for a coarse thread it may get interesting but you just start farther away from the thread so you can release the half nuts if needed. I usually thread at 75 rpm.

          From the photo's in the posts here some of the thread dials have to many numbers on them. The older lathes many times only had four lines on the dial. Most have 8 and that is plenty because you can always catch the engagement between the marks if the lead screw will do that but a coarse lead screw won't.

          If a dial has to many numbers then make a new dial with only 4 or 8 numbers and make it easy to use.

          I don't know how a Hardinge HLV threading system works but it must be expensive and for that reason not used on other lathes and it may be patented by Hardinge.

          I just don't see what is so hard about using the half nuts.
          Last edited by Carld; 02-01-2010, 09:35 AM.
          It's only ink and paper

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          • #6
            Hardinge yes, and also Hendey.
            No need for a thread dial with the single-dog clutch.
            Sort of a nice kept secret from the newbees reserved
            for the experienced machinist on real toolroom lathes.
            Newbees gotta learn threading the hard way first.
            That's just how it works!
            My 1917 Cataract toolroom lathe has it and
            my 1951 Hendey tool and gaugemaker's lathe has it.
            With these lathes, you can thread around 1000 rpm if you like.
            Thread finish looks excellent.

            --Doozer
            Last edited by Doozer; 02-01-2010, 09:48 AM.
            DZER

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            • #7
              Newby's, hell, most the machinists I have known have never seen or used a Hardinge lathe and they are a LONG way from being a newby.

              Are you refering to some elitist group or something related to Hardinge.
              It's only ink and paper

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              • #8
                I think it would be pretty cool to have the leadscrew on a stepper motor and not mechanically connected to the spindle. Computer would have to know the spindle angle and match carriage position to the thread.

                I bet that's how a CNC lathe works.
                If not, maybe we should build one.
                Mike

                My Dad always said, "If you want people to do things for you on the farm, you have to buy a machine they can sit on that does most of the work."

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                • #9
                  Hey, that's a good idea. Maybe you could use digital control motors and link them to a computer and design a program to do the machine work for you.

                  Now THAT is a novel idea and it may catch on. Should we call it computer controled machining, yes CCM works for me.

                  EDIT: Black_Moons, I'm just having a little fun with you, no harm intended but threading with a dial is not that hard.
                  Last edited by Carld; 02-01-2010, 09:53 AM.
                  It's only ink and paper

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                  • #10
                    Just pushing your buttons, Carl.
                    It's easier than threading on a Hardinge.

                    --Doozer
                    DZER

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                    • #11
                      Originally posted by Carld
                      Black_Moons, I'm just having a little fun with you, no harm intended but threading with a dial is not that hard.
                      I tried that once, and I couldn't get it to work at all.
                      So I gave up and put the toolbit back in, and that cut them just fine.


                      Peter

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                      • #12
                        Originally posted by Carld
                        I just don't see what is so hard about using the half nuts.
                        Ever cut a metric thread with an imperial lead screw, or vise versa?

                        Even if you've rigged up the right gear for the indicator, you might be waiting a long time for the marks to coincide.
                        Paul Compton
                        www.morini-mania.co.uk
                        http://www.youtube.com/user/EVguru

                        Comment


                        • #13
                          Yes, and you don't have to release the half nuts, in fact you can't release the half nuts but what has that to do with finding the right number on the dial.

                          Black_moons, that's a good one, I like that, it make me chuckle after I caught what you meant.
                          Last edited by Carld; 02-01-2010, 10:15 AM.
                          It's only ink and paper

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                          • #14
                            Originally posted by Carld
                            Isn't that what the half nuts do? Don't they engage the lead screw at the point you released them if you just look at the number on the thread dial? What is so hard about watching the number on the thread dial and engaging the halfnuts?
                            ...
                            I just don't see what is so hard about using the half nuts.

                            As the OP noted, there is usually an issue with the half-nuts when the leadscrew isn't the same language as the thread being cut, e.g. cutting a metric screw using an imperial leadscrew.

                            Plus, metric lathes generally need several little gears (interchangeable) for the threading dial to handle all the metric threads.

                            I added a dog clutch to my 7x12 and combined with a retracting tool holder it makes threading much faster and easier for both imperial and metric. I used to thread to a shoulder using a hand wheel, now I rely on the dog clutch and often thread at 300+ RPM. Higher speed seems to produce nicer threads on this little lathe.
                            See: http://www.gadgetbuilder.com/Dog_Clutch.html

                            John
                            Location: Newtown, CT USA

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                            • #15
                              Black_Moons, I have to agree that it seems like in several hundred years they could come up with an easier way to engage the lead screw and all the manufacturers could use it.

                              When you look at the lathe we use now and the lathes they used in the 1800's there is little difference except in the head stock. That is belt drive versus gear drive while the rest of the lathe is much like the early ones.

                              The more complicated it becomes the higher the price and failures of the mechanism can increase because of complicated workings. Sometimes trade off's are necessary.

                              In trying make it easy the makers that put all the marks on the dial only make it worse and complicate things. It would be much easier if they just made a simple dial with four marks and put all the rest on a chart.

                              I guess no matter how you do it if your confused your confused and I must say I have been confused by the chart too. For that reason I mostly use the number 1 when there are several to choose from. On the other hand, if you using a lathe with a worn lead screw you best use the same number all the time because if you engage a number that is supposed to work for that thread the worn lead screw can put you in the wrong spot in the thread and spoil the thread. Been there, done that. I don't trust old worn lathes and that is what most shops I worked in had. I guess it's a habit I developed to save my butt from slopping up a thread.
                              It's only ink and paper

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