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  • #16
    You will only have trouble with the chuck if a one of a couple things are true.

    First, obviously large diameter can produce a goodly torque, and could break the chuck loose.

    Second, vibration, interrupted cuts or the like, chatter, etc can break it loose even if the work diameter is less.

    I am inclined to not believe the stories of chucks at 600 rpm flying off the lathe and careening around the shop. In the first place, there is no reason other than threading to cut in reverse, and then also, few of us will thread at 600 rpm. If the chuck flies off at 600 rpm, it wasn't the only problem that was making trouble at the time.......
    CNC machines only go through the motions.

    Ideas expressed may be mine, or from anyone else in the universe.
    Not responsible for clerical errors. Or those made by lay people either.
    Number formats and units may be chosen at random depending on what day it is.
    I reserve the right to use a number system with any integer base without prior notice.
    Generalizations are understood to be "often" true, but not true in every case.

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    • #17
      Originally posted by flylo View Post
      Ever have a chuck come off?
      I have, not fun.

      People should look at the way Emco holds on their threaded chucks. A portion of the thread is split like a shaft collar so you can tighten down a screw that clamps the threads tight.

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      • #18
        Originally posted by J Tiers View Post
        You will only have trouble with the chuck if a one of a couple things are true.

        First, obviously large diameter can produce a goodly torque, and could break the chuck loose.

        Second, vibration, interrupted cuts or the like, chatter, etc can break it loose even if the work diameter is less.

        ...............
        I think a good set of braking resistors on a VFD would rate a solid third place.
        I personally have mine set to ramp down in 5 seconds. A 25 pound chuck at 1000 rpm is not something I want stopped in under 1 second! At least not with a threaded spindle.
        Home, down in the valley behind the Red Angus
        Bad Decisions Make Good Stories​

        Location: British Columbia

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        • #19
          Originally posted by J Tiers View Post
          In the first place, there is no reason other than threading to cut in reverse4
          Actually there is, if you want to avoid chatter issues and need feed toward the chuck, then you install your tool upside down. This way the forces try to bend the whole compound etc. upwards and away from the cut instead of in to the cut, thus preventing chatter. Have used this tehnique many times, most of them when doing work with a very large cutter like R5 or some large form cutting tool.

          What comes to threaded spindles, I do not support them as there is better things available.
          Amount of experience is in direct proportion to the value of broken equipment.

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          • #20
            ... and many others to accommodate tooling or other limitations, like reaching way to the rear to turn large disks, parting from the back, when angle facing out past center (sure, I could have messed around with tooling, but I didn't need to). I particularly like boring in reverse with inverted tooling - the chips fall down into the bore and shuffle out.

            I've done plenty of turning with threaded chucks in reverse, and with few problems. I had had a couple come "loose" (because I don't tighten then with "snap"), but they don't just fly off - if anything they float away from the spindle face slightly and get your attention quickly...
            Last edited by lakeside53; 09-29-2013, 03:13 AM.

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            • #21
              Originally posted by macona View Post
              I have, not fun.

              People should look at the way Emco holds on their threaded chucks. A portion of the thread is split like a shaft collar so you can tighten down a screw that clamps the threads tight.
              Yes, I've made a couple for Emco's. But.. to make this work well Emco has an extended shoulder on the spindle. The clamping acts on the shoulder, not the threads where asymmetrical pressure can throw the chuck off register. Also, to avoid moving the chuck, the back plate needs an accurate (close fit) shoulder area registration instead of "oversize" as is on many non-Emco back plates (where the register is the threads pulled against the spindle face). Applying Emco's technique is harder to do with some of the 1/8 inch shoulders on many threaded lathes.
              Last edited by lakeside53; 11-19-2013, 12:50 PM.

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              • #22
                Friend had a twelve foot diameter faceplate come off once, trundled down the shop knocked the double doors of then came to rest in the parking lot and never touched a car. Much pukka factor
                The difficult done right away. the impossible takes a little time.

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                • #23
                  Oldbrock,
                  I'll bet there was a line outside the mens showers.
                  Lucky no one was hurt , would have made a great educational video .

                  Michael

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                  • #24
                    Originally posted by Jaakko Fagerlund View Post
                    Actually there is, if you want to avoid chatter issues and need feed toward the chuck, then you install your tool upside down. This way the forces try to bend the whole compound etc. upwards and away from the cut instead of in to the cut, thus preventing chatter. Have used this tehnique many times, most of them when doing work with a very large cutter like R5 or some large form cutting tool.

                    What comes to threaded spindles, I do not support them as there is better things available.
                    Yes, that and part-off, but I did not bother to mention them. One comes up under the "chatter and vibration" heading, and part-off is not commonly done at 600 rpm in the home shop...... And anyone doing part-off on a reasonably large piece should already know the problem...

                    Personally, I have never noticed any difference in chatter etc running in reverse. If it chattered one way, it does something equally not-good in reverse with tool at back. If you have that problem, get rid of your single-phase machine.... go three phase and everything will suddenly work right.

                    Never did part-off from the back, it works fine from the front, with decent bearings and three phase.

                    Anyhow, most of that is special cases that don't come up much.... NOBODY could list them all if they tried.

                    Twelve foot faceplate? That wasn't threaded-on, unless you count the bolt threads..... (OK, "cap screws")

                    I HAVE seen a chuck loosen , but it did as Lakeside said... unscrewed slowly. Didn't get my attention quite that fast, I saw the result, not the cause, but I still shut it down 'cause something wasn't right. Then I saw the cause.

                    Bottom line is that it CAN happen, anytime in reverse, so plan for it. If you are ready for it, chances are it won't happen.
                    Last edited by J Tiers; 09-29-2013, 11:00 AM.
                    CNC machines only go through the motions.

                    Ideas expressed may be mine, or from anyone else in the universe.
                    Not responsible for clerical errors. Or those made by lay people either.
                    Number formats and units may be chosen at random depending on what day it is.
                    I reserve the right to use a number system with any integer base without prior notice.
                    Generalizations are understood to be "often" true, but not true in every case.

                    Comment


                    • #25
                      I also have Weiler equipment as mentioned by Cal in note #11 above and the threaded spindle LZ 330 lathe I have has this tightening collar. on a six inch chuck

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                      • #26
                        I cant claim ownership of the idea, but I fitted 3/8" soft-faced set screws located 90* apart on the threaded shoulder of my chuck mounting plates. They seem to work. I was worried about both the 8" 4-jaw and the 3-jaw on my Logan.
                        Duffy, Gatineau, Quebec

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                        • #27
                          I am glad to have found this thread. My HF 9x20 lathe has a setscrew on the chuck to keep it from coming loose when running in reverse, but I don't know how much torque it will take before losing grip. It is shown on page 13 of the manual:
                          http://manuals.harborfreight.com/man...5999/45861.pdf

                          I also notice that on page 36 it shows what appears to be the steady rest, but it is labeled the "traveling rest" which may be another word for the "follow rest". On page 7 it shows the follow rest labeled steady rest.

                          BTW, I wonder if the twelve foot diameter faceplate mentioned above was really 12 inches? I've seen videos and pictures of huge lathes, but...
                          http://pauleschoen.com/pix/PM08_P76_P54.png
                          Paul , P S Technology, Inc. and MrTibbs
                          USA Maryland 21030

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                          • #28
                            BTW, I wonder if the twelve foot diameter faceplate mentioned above was really 12 inches? I've seen videos and pictures of huge lathes, but...
                            I'm pretty sure Oldbrock knows what he's talking about, I don't think he would confuse 12" with 12'. At 12" he probably would not have brought up the story.

                            A large power chuck and a couple of faceplates on a couple of Chinese lathes.



                            Home, down in the valley behind the Red Angus
                            Bad Decisions Make Good Stories​

                            Location: British Columbia

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