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  • Auto stop for lathe

    I have seen adjustable auto stop devices on larger industrial lathes has anyone ever put that sort of thing on a smaller lathe , like a 12 x 36 or similar .

    I can see one being very useful when machining long shafting or threads .

    Also a good end stop so the chance of a crash is reduced.

    Michael

  • #2
    Yes - I wired up this micro switch. It triggers "stop" on my VFD.


    As you can see, it is very repeatable -- especially if you get the power braking on the VFD set correctly for the inertia of your chuck.


    For a "normal" screwcutting lathe, I see no reason not to rig a switch like this onto a standard bed stop. My contraption was largely inspired by the article, "Beyond the Basics with a Variable Frequency Drive" written by Dennis Hardin in The Home Shop Machinist magazine Vol.29, Number 3 (July / August 2010).

    If you are specifically talking about a mechanical auto-stop, you'll need to look into the book Screwcutting in the Lathe by Martin Cleeve. He presents the general principle. For an actual, built example, Graham Meek provides one in his book, Projects For Your Workshop Vol. 1. The plans only work on a Myford Super 7 gearbox, but it does provide a more concrete detail of the single tooth dog clutch mechanism.
    Last edited by Arthur.Marks; 03-08-2014, 11:47 PM.

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    • #3
      Many mechanical stops work by slowly opening the half-nuts on the carriage. That wears the half-nuts because they spend a lot of time partially engaged. It can't be good for the lead screw, either. A snap-release like the trigger of a gun solves the problem. There are some home shop web pages around the net that show DIY solutions to the problem. These work best when you can use a thread dial to pick up the thread. That is not always possible.

      Found it: http://andysmachines.weebly.com/semi...ddle-stop.html
      Last edited by dp; 03-09-2014, 01:17 AM.

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      • #4
        I made one for my lathe that activates the magnetic brake. I mostly use it as a safety device when I'm right up to the chuck or whatever. Saved me a few times. I still have concerns about stopping in the cut with carbide, but everything works well for what I do.

        Here's my original thread and pictures : http://bbs.homeshopmachinist.net/thr...der-worry-free!

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        • #5
          lakeside53, thats a good idea I will have to see if there is enough room to fit it ti the lathe in question.

          I was trying to fit a mechanical throwout for the switch that is already fitted to the machine .It is on the opposite side of the carriage.
          ArthurMarks , your idea is as good and I will see if something can be done , maybe some part of each .

          I have 6 rods 750 mm long to thread with a 12x1mm thread for a test jig, will get a bit boring towards the end

          Michael

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          • #6
            I have fitted an electrical autostop to my Sieg minilathe. This is very good for cutting shoulders and for screw cutting, see:
            http://mikesworkshop.weebly.com/autostop.html
            This autostop can switch off an auxilliary motor driving the lead screw, see:
            http://mikesworkshop.weebly.com/leadscrew-motor.html
            or the main lathe motor, see:
            http://mikesworkshop.weebly.com/lath...r-control.html
            Mike
            Last edited by drmico60; 03-09-2014, 09:12 AM.

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            • #7
              My old Holbrook, has an auto stop on the longitudinal feed shaft, it is a really nice arrangement when turning up to a shoulder At the front end of the saddle is a graduated adjustable screwed collar which is activated at the set point by a clamping collar on the feed shaft, By using this & the index on the top slide length measurements is no problem

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              • #8
                Most of the new import lathes have so many interlock switches that it's hard to get them going to start with. Not much effort to add in another switch and you may find, as on eg the Griz 9249 circuit diagram there is position in the connector strip that is just bridged with a wire waiting for another switch to be fitted.
                The Boxfords and therefore I assume old SBs has the friction clutch on the feed but assumes you stay awake for screwcutting. Has anyone considered fitting an adjustable ball bearing clickover clutch like on modern pistol drills?

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                • #9
                  MY lathe has an inbuilt stop feature which functions similar to this.On mine as soon as the carriage hits the carriage stop, the lever switch which sets the carriage in motion pops out and it stops imediately.So all you have to do is set the carriage micrometer stop where you wish the carriage to come to an abrupt halt, making sure of course to make sure you tighten the carriage stop very firmly , as once I had it move when the carriage made contact.Very fortunately I was close at hand I never walk away from any of my machines when they are operating even my mill which of course switches itself of too at the end of a run,I am simply too scared too. Alistair
                  Please excuse my typing as I have a form of parkinsons disease

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                  • #10
                    Logan made and sold a device that opened the halfnuts. It's shown in their old catalogs.

                    It was a spring trigger type, where the plunger released a spring arm that opened the halfnuts. As DP mentioned the slow type put a lot of wear on things. Not only that, they are not very consistent about the opening point. The trigger type can be very consistent.

                    Logan advertised it as a way for one man to operate several machines, so it was obviously intended to operate without immediate attention.
                    1601 2137 5683 1002 1437

                    Keep eye on ball.
                    Hashim Khan

                    If you look closely at a digital signal, you find out it is really analog......

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                    • #11
                      The Nardini 12 x 30 comes with a trigger type trip device on both the horizontal feed and the cross feed. The adjustable stop is shown here.

                      The stop pushes the trigger button shown in the photo.
                      For threading the micro switch shown here activates the solenoid brake.

                      The micro switch should be workable with a VFD but Nardini is worth sherching for. Wish mine was a 14 X 40.
                      Byron Boucher
                      Burnet, TX

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                      • #12
                        I have a question about threading up to a shoulder. If you put your threading tool on the other side of the round stock, turn your lathe in reverse and start from the shoulder towards the tailstock direction would it come out right or left hand threads ??

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                        • #13
                          You would get right handed threads.
                          Location: Long Island, N.Y.

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                          • #14
                            The microswitch suggestions are great , but I vaguely remember a collar on the clutch lever which somehow knocked the feeds out of gear when threading or machining up to a shoulder.

                            I will try a switch that's easier.

                            Michael

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                            • #15
                              I remember the safety gurus wanting a dc injection bake system fitted to all rotating machines in the machine shop, sounded good but some chucks were screw fitted! There was a big craven lathe with a 6foot swing, the injection brake worked, the machine stopped but someone forgot to tell the faceplate!, it screwed off quite dramaticaly as the safety department watched, a very large lump of iron hit the bed and fell over smashing the top of the carrige to bits.
                              Solution, that machine was unsafe, should be scrapped say the safety department, ok says the engineer we will, will you fund a replacement, of course they say till they found out how much a 30 foot long 6 foot swing craven lathe cost, reconditioned.
                              We had to repair it soon after, including a toasted motor and drive train.
                              Moral is if its screwed on ii can screw off i think!
                              Mark

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