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Accidentally Spun A Chuck On Under Power

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  • #16
    I did that once in my early days. Wound up pulling the spindle out of the machine and took it to the high school metal shop where I spent my Wednesday evenings. (Community college class for adults.) I made a pair of jaws with a key to hold the spindle by the left end, vertically in a bench vise. Then laid a six foot long steel bar across the face of the chuck between the jaws. Another person and I pulling mightily on the ends were able to free the chuck without damage. However, an earlier attempt at removal had broken some teeth on the bull gear and its mating gear. I had to completely rebuild the back gear set. Perhaps I could have come up with an in situ chuck removal method, as you did, but I had to pull the spindle to repair the gears anyway. Hard lesson. I haven't repeated that mistake.

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    • #17
      Originally posted by junkaddict View Post
      I turned on the lathe without the chuck all the way on. I was centering a piece in a 4 jaw, and had backed it off without noticing. Well, I knew it was going to be trouble as soon as I heard the whack of the chuck seating. I tried everything. Impact on a piece of hex bar, piece of plywood against the bed and a socket & breaker bar on hex stock bumping it in reverse. It was not budging, and I know better than to try the back gear. I though about it, and was looking at the hole in the end of the spindle where a collet closer pins on. I though if I could make an inner and outer diameter that just fit on the spindle end like a socket so there was no room for anything to deform in any direction, and I put a pin though all three pieces, that pin in shear like that would take a fair amount of force without breaking. A little turning, welding, drilling, and voilĂ ! Locked it solid, and it came off. Took a dial gauge to it, and it is still straight. Wasted an entire day. There is a mistake I wont make again.
      Originally posted by Mcgyver View Post
      Just like you did, I figured the trick is support the pin right at the shaft. I had one, looks like it was glued on, that really taxed me. braces and belt maybe , but I made something that both clamped on the shaft and engaged the pin. Not to suggest you were wailing on it, but learned with a few projects recently that 100 or 500 or whatever little taps can often free something up vs one big one that breaks things. Its amazing how well it can work. 24: adjustable on the clamp, big pipe wrench on the stuck collect chuck....I was worried about the amount of torque required bending something, but no harm done, spindle was 1/2 a tenth run out afterward
      Unfortunately things like an over-tightened chuck happen from time to time. On behalf of those who might someday experience this malady, Thank You to both of you for taking the time to post pictures of how you resolved the issue successfully. Hard to beat the help of quality photos when trying to explain things.


      "................but learned with a few projects recently that 100 or 500 or whatever little taps can often free something up vs one big one that breaks things."

      Yes! This is a valuable technique. This is where I often use an air chisel gun to provide the "little taps". Just hook up the gun through a pressure regulator first. Use a flat hammer attachment in the gun. Start near zero psi and slowly increase air pressure until the gun provides gentile taps against the work piece. I only recommend doing this if the gun is controlled through a pressure regulator.

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      • #18


        Several years back I bought an old (1944 - wartime plaque and all) 9" South Bend lathe and the chuck on it was severely stuck; I tried everything (except dry ice in the spindle) including building a clamp to secure the outboard end and using a 3/4" impact gun on a large piece of hex shaft in the jaws while I reefed on a 12" crescent wrench on one of the jaws. All I managed to do was twist off my 3/4" to 1/2" adapter. I ended up hacksawing through the back plate as close as I could to the spindle which worked and with so little material removed, I saved the back plate too. The chuck scroll and teeth on the jaws were severely worn so I wasn't worried about damaging the chuck.
        Location: Saskatoon, Saskatchewan, Canada

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        • #19
          Don't sweat it...... Just as R.P.W pointed out, an interrupted cut can make the chuck tighter than starting up with it loose. Talk about a lot of little taps....! I've had that happen. Not a big screwup, just another workshop hassle, and you did a good save on it. Thumbs up on that!

          It'll happen again from something like an interrupted cut, and you now have the tools to handle it. Not uncommon, and another really good reason why L type and Camloc chucks exist. No interrupted cut it tightening a Camloc.......... I'd prefer to have machines with those...but I don't at the moment.

          I really like the "how I handled this" type posts. Shows folks are thinking, and provides good ideas. I know I do not like the mega threads, but this is really a contender to be the beginning of one... It would get all the "how I saved this situation" posts in one spot. I'd guess there won't be as many as the SMT megathread!
          CNC machines only go through the motions

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          • #20
            I posted this some time ago, but it is worth posting again. In it I did free a stuck chuck without resorting to excessive force or endangering the back gears.

            I think I may have stumbled on something that actually worked. I had been trying, on and off for some time but it just wouldn't budge. I soaked it with Kroil a bunch of times and let it sit, trying to free it the next day. I have seen so many lathes on E-Bay with one or two broken teeth on the back gears so there was no way that I was going to use the back gears in this endeavor, or so I thought. In the past two days I intensified my efforts because I have a backlog of several projects that need some lathe work. Yesterday I started trying to use some shock treatment with a wood block against the jaws and a one pound hammer. But I did not use the back gears, I just used the motor with the pulleys set for their slowest speed to resist the blows. Still, it did not come free.

            Yesterday I thought of trying an application of WD-40 on top of the Kroil that I had applied the previous two days. It did not work yesterday. But tonight I was trying to set up to try the technique suggested by Mr Borton in a post on the SB forum at Practical Machinist, link below. His technique was to lock the gears and put a weight on a long lever arm on the chuck. Then go to bed and check it the next day.

            I found a pipe clamp with a four or five foot section of pipe and I was clamping it to one of the chuck's jaws. I had locked the rotation with the back gears because I felt that this was fairly safe if I was not going to apply a lot of weight or hammer on it. So I got the pipe clamp on the chuck (with some cardboard to protect the chuck) and I decided to just put a little pressure on the pipe, and not even at the far end, only about two feet from the chuck. I pushed down with a moderate amount of force and, BINGO, the chuck unscrewed as easy as you please.

            Now I can not say exactly what did it. Was it the accumulation of a couple of days of hammering? Was it the Kroil, finally working? Was it the combination of Kroil and WD-40? I really can not say. But if this happens again, you can bet that I will be trying that combination of oils again. Take it for what it is worth. It is certainly worth trying before other methods that may be potentially more harmful.

            https://www.practicalmachinist.com/v...ml#post3564965

            Paul A.
            SE Texas

            And if you look REAL close at an analog signal,
            You will find that it has discrete steps.

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            • #21
              As Sir John would say..... "Clumbsy Bastard!"

              God I miss that guy here !

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              • #22
                Happened to me as well a bunch of years ago. Soth Bend 10L w/ 2-1/4 x 8 tpi threaded spindle. Slightly different method to get it off, but similar just as well. See the link to "Clemson's" post in the 2nd post in this thread, for pictures...

                https://www.practicalmachinist.com/v...rusted-165617/
                Last edited by morsetaper2; 05-08-2021, 09:44 AM.

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                • #23
                  I spun one on too tight before. I did like you and made a tool, except it took advantage of two teeth in the bullgear. A guy on FB had said about making such a tool weeks before, I'd have never known about it without his heads up.

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                  21" Royersford Excelsior CamelBack Drillpress Restoration
                  1943 Sidney 16x54 Lathe Restoration

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                  • #24
                    It hasn't happened to me personally, but a variation has which I apologise for having mentioned in the past. I used to work for a small firm which used to do a lot of work refurbishing stuff for the Ministry of Defence. Mainly obsolete things where the original manufacturers were no longer around. The boss thought a new lathe to suppliment the old Myford ML7 would be a good idea. A brand new Myford Super 7 arrived, single phase which was nice. The stupid charge hand who thought he knew everything switched it on and the 4" Pratt chuck which was not tight on the spindle, unscrewed as the lathe was in reverse. The chuck bounced of the bed, over the tray and hit the floor close to the ideot's foot. I had to stone a bruise of the bed of a lathe that had not yet cut any metal. That little chuck was exceptional, it always ran 0.001" tir or better.

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                    • #25
                      Originally posted by old mart View Post
                      It hasn't happened to me personally, but a variation has which I apologise for having mentioned in the past. I used to work for a small firm which used to do a lot of work refurbishing stuff for the Ministry of Defence. That little chuck was exceptional, it always ran 0.001" tir or better.
                      OT, but thanks Old Mart ! Much appreciated -- I don't know if you saw my pm. Reference material like that is always welcome and useful.
                      25 miles north of Buffalo NY, USA

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                      • #26
                        Originally posted by nickel-city-fab View Post

                        OT, but thanks Old Mart ! Much appreciated -- I don't know if you saw my pm. Reference material like that is always welcome and useful.
                        I haven't had any pm's, but if you are refering to the Zeus book and thread wheel I put in the post on the 23rd of March, I thought it was long lost. Be careful with wire gauges, though, there are so many variations.

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                        • #27
                          Next time try heating the chuck as hot as you feel comfortable, and with the machine running at low rpm force a block of ice in the spindle taper so that it melts quickly and has good contact area.


                          Then quickly shut off and lock spindle and apply torque to the chuck.

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                          • #28
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                            This works well on this style of SB 9 inch. I whittled it out of 1/4" plate and it immobilises the spindle well.
                            It fits on a cast boss of the bull gear opposite from the back gear drive pin.

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                            • #29
                              Great to see the variations in solving the problem, keep them coming.

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