Securing a threaded on chuck for reverse rotation
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    Default Securing a threaded on chuck for reverse rotation

    Good evening,

    I do little gun smithing but I note this forum is more accommodating of Asian machine discussions than the general forum so I thought I would ask the following:

    I have a Grizzly 12X37 lathe (along with an SB Model A and Wells Index 747 mill, and access to a Lodge and Shipley 18X54.) Do the latter get me a pass, Don?

    I prefer to thread from the head stock out so I want to secure the chuck for reverse operations.

    There is room to drill and tap the back plate on the three and four jaw chucks I have to 3/8"-16.

    So my thought is a dog point or cup point set screw securing the chuck. (not on the spindle threads, obviously).

    I thought about using a brass or lead plug under the screws but abandoned that as there is only .500" depth to work with.

    Three at 120 degrees should to the job?

    I know the spindle is hardened. I know how to not over tighten a chuck on the spindle

    Typically I don't take heavy cuts when threading and grooving.

    So wattaya think?

    Tony

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    Both of my lathes have threaded spindles (although the back plate seems to be frozen to the spindle on the older machine) and I have not had any problems with the spindle unscrewing while running in reverse. But neither machine has any way of braking the spindle so hard that the chuck will unscrew. Also, the old machine won't go very fast so the chuck does not acquire a great deal of angular momentum. If threading is your only need for reverse, I doubt you will be running so fast as to unscrew on starting, either.

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    Good morning,

    Good points. I had thought of that particularly starting. The green machine has an eight inch four jaw that is pretty heavy. (for the size of the machine.) The machine is capable of thirteen hundred rpm but I seldom go beyond nine hundred. I swap chucks fairly often and don't secure them gorilla tight. It's making a 1"-2" long deep cut in the middle of a shaft that I'm thinking about. If the tool jams.......Obviously a follow rest or steady rest helps. There are times when I could get away without the extra work setting up the rest to eliminate noise and chatter. And.... Threading in reverse gives the option of increasing the speed without the fear of crashing to get a better finish and not having to cut a relief at the end of the thread.

    I think I'll drill and tap for a couple of set screws over brass slugs (that I'll have hunt down in the chip pan and on the floor every time I switch chucks) in the back plate. Peace of mind, I guess.

    A little off topic:

    In the 70s a machinist who had spent thirty plus years at CAT showed me how to thread from the head stock out. Same for running in reverse cutting wide deep grooves in nasty or hard materials. In addition, replacing a live center with a dead center when all else fails to control noise and chatter. I was in his shop on a day when he did it. Later, beer in hand, I remarked that I couldn't feel much if any play in the live center. His only comment was, "It doesn't take much". ENd of discussion.

    Thanks for responding.

    Tony

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    I don't thread out from the chuck.. but if I did I would keep RPM low...
    I have used a lot of threaded spindles and have not lost a chuck.

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    You CAN get set screws with a inserted soft tip !

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    The better back plate /chuck designs usually used split collars to prevent unscrewing.
    Attached Thumbnails Attached Thumbnails emco-face-plate-1.jpg   emco-face-plate.jpg  

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    Quote Originally Posted by Andy St View Post
    The better back plate /chuck designs usually used split collars to prevent unscrewing.
    Some among us settled for a strategically placed slice of copper or aluminium foil, "company lathe" and no messing about with set screws allowed.

    Don't leave it in there after the job is done, though. Bubba is only criticized when his jackleg tricks to JFDI and git 'er DONE are caught-out a year later when the chuck ain't COMING off when one wants it to.

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    Quote Originally Posted by thermite View Post
    Some among us settled for a strategically placed slice of copper or aluminium foil, "company lathe" and no messing about with set screws allowed.

    Don't leave it in there after the job is done, though. Bubba is only criticized when his jackleg tricks to JFDI and git 'er DONE are caught-out a year later when the chuck ain't COMING off when one wants it to.
    Please elaborate. I'm interested.

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    Quote Originally Posted by Yan Wo View Post
    Please elaborate. I'm interested.
    Lessee... late 1950's. SB 10" & Logan. 2 and something 8 per if old memory serves.

    Copper foil was thin strip, VERY! Not wide atall, no ROOM for it otherwise, and it is wedged, chuck not actually allowed to go 100% onto the register shape at the rear.

    OTOH, it dasn't offer to come off easily, either.

    Downside was it took expertise to PLACE it just-so. Upside is it was easily portable, later, to Day Job where the machines were not mine.

    The "School solution" we worked out later was better - took no skill. We cut a narrow, large-bore "washer', of 26 ga. soft aluminium and put it on first, chuck second. Didn't even affect TIR all that much, and it was a school, so TIR didn't matter as much has "concept". And safety of school-age kids. Started 'em younger back when their Dad's were working for mills and such. Or RAN them. A classmate's Dad was CFO, Mesta Machine. His Uncle Louie was CEO. Rank and file or ULM, all still recognized metal working as a valuable skill, whether one worked at it or hired those who hired those who hired it done.

    That "washer" TOTALLY stopped the chronic pranksters that would push the "REV" button of a 3-Phase 3/4 HP instant-reversing motor at full-gallop to roll a chuck at the feet of their classmates.

    And the SB even more than the Logan would DO that, and with great reliability before we added the washer.

    Most ere sayin' it ain't a problem are not bored school kids trying to MAKE it happen, is all.

    Meanwhile - glad to have seen the back of threaded noses altogether, but that was as much luck as planning.

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    Quote Originally Posted by GGaskill View Post
    Both of my lathes have threaded spindles (although the back plate seems to be frozen to the spindle on the older machine) and I have not had any problems with the spindle unscrewing while running in reverse. But neither machine has any way of braking the spindle so hard that the chuck will unscrew. Also, the old machine won't go very fast so the chuck does not acquire a great deal of angular momentum. If threading is your only need for reverse, I doubt you will be running so fast as to unscrew on starting, either.
    My 11x24 Kerry has also threaded chuck. I thought that its not a problem until it once got loose on threading operation... NOT fun when 160mm chuck is spinning on lathe ways and jumps towards your toes!
    Thanks to fast reflexes my toes are still intact but the ways took couple of extra dents.

    I added split ring to clamp on the collar. Kind of hard to believe at first but I didn't need to split the collar, it's very close fitting so just tightening the ring around the chuck collar locks it in place.

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    Quote Originally Posted by MattiJ View Post
    My 11x24 Kerry has also threaded chuck. I thought that its not a problem until it once got loose on threading operation... NOT fun when 160mm chuck is spinning on lathe ways and jumps towards your toes!
    Thanks to fast reflexes my toes are still intact but the ways took couple of extra dents.

    I added split ring to clamp on the collar. Kind of hard to believe at first but I didn't need to split the collar, it's very close fitting so just tightening the ring around the chuck collar locks it in place.
    I agree with MattiJ on this. If the back plate is a good fit to the register just a split collar will do, no need to split the back plate / mount. One problem is that not all lathes with lets say 1 1/2" 8tpi have exactly the same size register. So a third party chuck might fit a South bend correctly but not a Rockwell.

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    Quote Originally Posted by JohnEvans View Post
    You CAN get set screws with a inserted soft tip !

    Arrrgggg! Forgot about them. Thanks for the reminder.

    Tony

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    Quote Originally Posted by tcom View Post
    Arrrgggg! Forgot about them. Thanks for the reminder.

    Tony
    Or you can make them

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    Quote Originally Posted by Brodytonelotti View Post
    Or you can make them
    ... or thumbtacks.. or Bostich staples...or 4-penny box nails .. but WHY?

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    Quote Originally Posted by thermite View Post
    ... or thumbtacks.. or Bostich staples...or 4-penny box nails .. but WHY?
    First of all none of your examples are really that easy to make quickly. On the other hand what I meant was if you already have the right size set screw and some brass laying around it doesn’t take any time at all to drill a hole in the end of the set screw and press in a piece of brass. I’ve done it many times and it takes a lot less time than having to run to the store or wait to get one in the mail just to finish a job or in this case start one. I agree there is no reason to make a set screw completely from scratch if you can buy one. That wasn’t what I meant

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    My brother had his Logan lathe start up in a high gear in reverse, I think he was wiring it up. The chuck came off and put a divot in the bed in front of the chuck.
    He asked what I'd do and I suggested drilling and tapping a couple of holes for setscrews, what they call conical point setscrews, and make slight divots in the spindle clocked so that tightening the setscrews actually pulled it tighter.
    Of course then you have small set screw divots in the spindle, but even if you changed chucks some day the new chuck could be drilled to line up with them, not easy but possible.
    Another thought is to go ahead and drill/tap for setscrews to run directly down to the threads, but make a bronze plug that fits the threads with the thread form, this plug being what the setscrews press against.

    I've actually done that before but I don't remember what it was, not a chuck though. You'd have to super glue it in the tapped hole before you thread the back plate, then, when the final perfect thread fit is found just install the setscrews, that should be plenty to break the super glue.

    But even easier is to drop a lead ball in before the setscrew, it conforms to the thread form without harming the threads and yet holds well.

    But of all the ideas proffered here I like the split collar the best, it would have the same effect as shrinking the backplate on (Which they used to do also, the chuck having to be machined off at new chuck time), but the collar would be releasable.

    My old Sculfort lathe with it's 16" chuck has a key cut radially into the back face of the collar. Behind that on the spindle is a split collar made with a projecting key built in, and that is inserted into the radial keyseat of the chuck's back plate and then the split bolt tightened so it grabs the spindle tight. That also works very well, but you can imagine with a 16" chuck there is a lot more room behind the chuck to do this than on smaller lathes.

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    There are other ways. One of my lathes uses a groove in the spindle and a keeper that is screwed to the chuck's adapter.

    The first picture shows the keeper in place on the chuck. Second shows the groove on the spindle. Third shows the mounted chuck and the keeper in use.






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    What a bunch of Nancy boys. Every one worries about the threaded chuck flying off, WHY? I have been using my 16" south bend since the late 70's, Plug stopping the spindle with 6" and 12" chucks, threading left and right hand threads, on and on. One common denominator, the chuck has never come loose let alone falling off. The spindle and chuck are not butchered with set screws, pins or anything else. Screw your chuck on, when it stops, back up about 15-20 degrees then quickly turn the chuck till it thumps to a stop, it is not going to fall off.

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    MM, that's very nice for you. My brother dinged his ways when his chuck spun off, that wasn't a nice day at all for him.

    All my lathes except the big Scufort have D type spindles, and I've often wondered if such high pucker experiences may be why the superior D and L spindles were invented, and why it's hard to find a new lathe with 3 HP or more that has a screw on spindle.
    I do have a few lathes in storage that have screw spindle noses, old antiques. I'd really be all "nancy" using one running in reverse working on an interrupted cut, It's nice to not have to worry about it with a camlock nose,

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    Quote Originally Posted by partsproduction View Post
    MM, that's very nice for you. My brother dinged his ways when his chuck spun off, that wasn't a nice day at all for him.

    All my lathes except the big Scufort have D type spindles, and I've often wondered if such high pucker experiences may be why the superior D and L spindles were invented, and why it's hard to find a new lathe with 3 HP or more that has a screw on spindle.
    I do have a few lathes in storage that have screw spindle noses, old antiques. I'd really be all "nancy" using one running in reverse working on an interrupted cut, It's nice to not have to worry about it with a camlock nose,
    The modern chuck mounts are required because modern high horsepower gear head machines accelerate and stop the spindle fast enough that it may come loose. Old lathes and flat belts don't have that problem. My bet is that your brothers chuck was loose. Started unexpectedly while wiring it! WTF! Lets just wire this machine with the machine switch on and live power wires. You betcha.


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