Myford S7 Chuck Lock

Discussion in 'Machine Modifications' started by SteveT, Feb 7, 2019.

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  1. Feb 7, 2019 #1

    SteveT

    SteveT

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    I could really do with turning some small items with the lathe running in reverse. This of course risks the chuck unscrewing.
    Has anyone come up with a workable solution to secure the chuck other than that used on the big bore Myfords which would mean modifying the spindle nose.
    Any suggestions gratefully received
    Steve T
     
  2. Feb 7, 2019 #2

    tornitore45

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    I placed 3 set screws in the backplate collar but practically never tighten when changing chuck. However they are there just as last ditch precaution for those rare case I need to run in reverse and even then I take light cut and use the tail stock if I can.
     
  3. Feb 7, 2019 #3

    goldstar31

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    Why one needs to run a lathe in reverse eludes me. Perhaps you can explain.

    I DO have a rear tool post for parting off which arguably beats all other methods. Mine is a Geo Thomas design which is pretty common to Myford users. True, I have a number of chucks, faceplates, catchplates and collets but that is 'run of the mill 'stuff which most of us collect over the years.

    I haven't got around to having/making a Keats plate but I have a ready supply of scrap metal to pepper with assorted holes, tapped or otherwise as an alternative. Again, this is quite normal.

    I DO have rather opposite problems with chucks sticking and consequently made up a jig of sorts to release annoying catch plates- to belt with a hammer when gentler persuasion methods fail.

    So please add to whatever experiences encountered.

    Norman
     
  4. Feb 7, 2019 #4

    mcostello

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    Some of Us have no where to mount a rear tool post.
     
  5. Feb 7, 2019 #5

    TonyM

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    Running in reverse is easier for internal screwcutting in a blind hole.
     
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  6. Feb 7, 2019 #6

    Apprentice707

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    If it is a round bar you wish to turn I suggest using a genuine Myford system collet. I have never had any problems with one of those coming loose. The ER system may be good too, but I have never tried that.

    Good Luck

    B
     
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  7. Feb 7, 2019 #7

    tornitore45

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    RH Threading a blind hole is easier in reverse.

    I never got a chuck stuck on the spindle. I place a pin wrench on the spindle and lean it over the front way. Then an adjustable wrench on one jaw. Very little effort required.
     
  8. Feb 7, 2019 #8

    SteveT

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    As others have said I have some internal screwcutting in blind holes but also some matching male and female tapers.
    Thanks to everyone who has responded.
    Steve T
     
  9. Feb 8, 2019 #9

    Wizard69

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    You didn't define what is meant by small but frankly a Morse taper adapter to a ER collet is a very good way to handle smalls.

    I otherwise understand your situation, I have a generic 9x20 and the biggest problem with this lathe is in fact the screw on chuck. Back when i bought it I did some research so I knew what i was getting but the problem was many did not highlight the issues with a screw on chuck. Frankly I don't see a good way to run such machines in revers with a chuck mounted. If anybody was to ask me today I would say avoid machines with screw on chucks. It is too late for us, but I'm certain newer users out there would at least like to consider the opinion.
     
  10. Feb 8, 2019 #10

    BaronJ

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    Hi Guys,

    I have a Myford S7 with a screw on chuck, and never had a problem with the chuck coming loose, never mind unscrewing ! I do a lot of work running in reverse, particularly threading. Both internal and external. The loading when threading is so small that unscrewing the chuck is a non issue.

    I fact I don't know anybody that has had a chuck loosen on them ! Though I agree that it could happen and people should be aware of the possibility.

    With regard to the Myford only, my S7 has a spindle lock pin that is intended to be used when removing the chuck, however I find it easier to use the back gear to lock the spindle.
     
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  11. Feb 8, 2019 #11

    BaronJ

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    Hi Norman,

    I trust you are keeping well.

    It is very important that the spindle register and threads, and the matching ones in the chuck are undamaged and kept scrupulously clean and well lubricated. Something as little and thin as a hair can cause the chuck to bind on the register.

    A guy near me had the chuck stick on his machine ! It turned out that he had cleaned the threads in the backplate with a paper towel and some of it had ragged on the threads. No noticeable difference screwing it on but a real pig to remove.
     
  12. Feb 8, 2019 #12

    bobden72

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    Number one is cutting a left hand thread! I have never had a problem of the chuck unscrewing its usually the other way trying to get it off.
     
  13. Feb 8, 2019 #13

    WOB

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    I wind springs in reverse because I like to watch the turns going on the mandrel over the top. I also power tap with a tap in the tailstock. Reverse makes backing out the tap fast and easy.

    WOB
     
  14. Feb 8, 2019 #14

    mcostello

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    I have had a chuck unscrew 2 times, the second time I caught it in time.:eek: I have also had it once be a real pig to remove.
     
  15. Feb 10, 2019 #15

    dazz

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    Hi
    Running a lathe in reverse with a threaded spindle is like driving down the wrong side of the road. Sooner or later, it is going to end in tears.
    One of many reasons for reverse running is external or internal threading from a shoulder.
     
  16. Feb 10, 2019 #16

    DJP

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    I had this happen on a previous lathe. The chuck backed out enough to jam the cutter and the belt then slipped. The long threaded spindle for the chuck seemed to be a design feature should the chuck start to unscrew. The chuck on that lathe was also small so mostly I got a surprise and no real damage.

    In the industrial world with huge machines the risk goes way up.
     
  17. Feb 10, 2019 #17

    Hopper

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    I cut left hand threads using conventional forward rotation. Just start the thread at the chuck end and cut towards the tailstock. Likewise for cutting tapers, intsead of reverse rotation, I turn the boring bar upside down and cut on the back side of the job.

    But there are a couple ways to secure a Myfraud chuck, depending on model and format. If the chuck or backplate has a smaller diameter hole in the rear than in the area where the jaws run, you can put a disc in there attached to a long threaded rod down through the centre of the lathe spindle with a nut and washer on the other end, kind of like a draw bar. Disadvantage is you can't run a long job up through the spindle hole.

    Other than that, you could drill and tap a couple holes through the chuck or backplate collar, depending on model, and put in a couple of grub screws with brass tips that bear on the spindle thread and stop the chuck unscrewing.

    Or you could keep the tailstock centre in place, with tailstock locked down hard, which should - in theory - stop the chuck from unscrewing and moving toward the tailstock. In theory...
     
    Last edited: Feb 10, 2019
  18. Feb 10, 2019 #18

    BaronJ

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    Hi Guys,

    I'm somewhat surprised by the comments that people have had the chuck unscrew on them !

    A properly fitted chuck requires a fair amount of force to unscrew it, as can be seen when it comes to changing it.

    The only scenario that springs to mind that could cause a chuck to loosen, is parting off from a rear tool post with the parting blade the wrong way up ! Unfortunately I've seen people with machines set up like that. Possibly because most advice to parting issues is to "part from the rear" without stating that the lathe should run in the normal direction and that the parting tool should be fitted upside down.

    Of course it could be that the chuck hasn't been screwed up to the shoulder properly.
     
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  19. Feb 10, 2019 #19

    goldstar31

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    Of course, John, no one has mentioned the fact that Myford spindles have a register. o_O
     
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  20. Apr 3, 2019 #20

    Baz

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    If I remember correctly the new big bore Myford has a groove in the spindle register and the back plates have a grubscrew which locates in said groove the idea being to prevent the chuck unscrewing when run in reverse, never actually seen it in real life though because big bore Myfords are a bit too expensive for my pockets!
    Baz
     

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