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South Bend Heavy 10 Chuck Problem

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  • South Bend Heavy 10 Chuck Problem

    We have a South Bend Heavy 10 lathe in a common area which can be used by several people. The last person to use the lathe left the four jaw chuck on the lathe. The chuck is a screw on/off and the chuck must have been tightened by an 800 lb. gorilla! I've soaked the threads with penetrating oil and it has sat for 24 hours. I normally engage the back gear to hold the shaft stationary while the lathe chuck is unscrewed with a wrench on one of the chuck jaws. The chuck is on so tight, I afraid I will break the teeth on the back gear if I put too much torque on the chuck to try to break it free. I've already bent a 1/2" by 1/2" foot long bar trying to break the chuck free. Does anyone have suggestions on how to remove the stuck chuck without breaking the back gear teeth? Thanks in advance.
    Bill

    Being ROAD KILL on the Information Super Highway and Electronically Challenged really SUCKS!!

    Every problem can be solved through the proper application of explosives, duct tape, teflon, WD-40, or any combo of the aforementioned items.

  • #2
    Dont use the back gear!! JR

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    • #3
      I got my 10l knowing one or two teeth were missing from the BG. It is a matter of grasping the spindle proper then think about short rotational impacts, what do they call those.

      So wrench up the 1/2" air drive with a 1/2 sawed off blank. Chuck it up in the lathe chuck and give it a couple hits with the air gun. Light taps (make sure you have your directions correct).

      It might pop right off. JR

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      • #4
        stick an ice cube in the spindle.

        back gear teeth on a southbend 9 are 16 dimetrical pitch 5/8" wide, made from 30,000 psi cast iron can handle 40-50 foot pounds continuously, the cast iron teeth have a good chance of breaking above 100 foot pounds, are nearly guaranteed to break at 150 foot pounds of torque... know your limits.
        Last edited by johansen; 09-06-2019, 04:25 AM.

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        • #5
          Does the spindle have a collar visible between the backplate and the bearing housing? If so, you could try drilling a blind hole into the collar and making a Cee spanner to fit. Worst case scenario is to take the chuck off the backplate and machine the backplate to dust. Don't risk the backgears any more than you have done already.

          When I was reconditioning my UK made Raglan, (these seemed to be susceptible to broken back gear teeth) and had the spindle out, I machined 2 flats on the collar and made a big spanner out of steel plate. With the end of the spanner resting against the bed casting, a smart tap on a spanner on a chuck jaw always worked. Then the big plate spanner jumped off, and fell on my feet----.
          'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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          • #6
            Yeah, don't break the back gear. Much better not to use it for this. I wonder if there is debris in the threads..

            This question comes up regularly. Lots of good info out there, and there is some awful advice mixed in! There was a thread on PM in the past 6 mos where someone had purchased an old lathe and the chuck had been on for potentially decades. That was a great read, as the OP tried various techniques. I couldn't locate the thread. There were also concerns that there might be buried set screws locking the chuck on. His chuck was surely much more stuck than yours, fortunately.

            There is the fundamental question of whether smooth torque can solve this, or whether a more abusive impact approach - whether hammer or otherwise - is required. Much better to be smooth about it, especially on a small lathe like this.

            He clamped a bar to the opposite end of the spindle to prevent it from turning. His first bar was hollow, like a stop sign, and the flex was too great for it to work - it was feeble. Bolts were undersize, clamp material was aluminum. He eventually had to upgrade all that. But something light might work for you.

            You can clamp a piece of metal in the chuck, and either allow it to rest against the bed and fix the chuck, or you can use it to turn the chuck.

            Have you tried a strap wrench on the chuck and on a spindle gear? They are sorta feeble, but possibly.

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            • #7
              the youtube guy Mrpete222 did several videos on just that subject.
              one way was to make a internal mandrel to go up inside the spindle and hold it.
              And, use a impact hit rather than just a cheater bar to break loose the thread

              Comment


              • #8
                Take a look at this post: https://www.hobby-machinist.com/thre...1/#post-555123

                Using the back gear to lock the spindle to remove a stuck chuck is almost guaranteed to break off teeth on the gear. Build the spindle crank and you'll be able to lock the spindle without destroying the back gear.

                In the future, cut a washer out of wax paper or parchment paper and place that between the chuck and the spindle face. This is a trick used by the British for their lathes on ships to prevent locked chucks.

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                • #9
                  Thanks for the ideas. It is now off to the shop to try to see which one will work the best. Paper spacer on spindle shaft will be mandatory in the future!
                  Bill

                  Being ROAD KILL on the Information Super Highway and Electronically Challenged really SUCKS!!

                  Every problem can be solved through the proper application of explosives, duct tape, teflon, WD-40, or any combo of the aforementioned items.

                  Comment


                  • #10
                    The person who last tightened the chuck need not have been a gorilla, if you screw up the chuck until it is 1/4 turn from tight and then spin it on, the inertia will do the rest. Rather than an ice cube in the spindle, you might try heat from a heat gun blowing through the spindle bore. If the length of the spindle threads to the register face increased even a tiny bit, the chuck might not be so tight. I have long since stopped jarring the threads loose on the Smart & Brown and prefer using a strap wrench. If you jam the back gear with a wad of cloth and keep a steady pressure on the chuck with a strap wrench while heating the bore of the spindle, it might work.

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                    • #11
                      Hmm. I'm not convinced about blowing hot air up the spindle bore. Seems to me that would just expand the spindle and make the chuck even tighter. Possibly hot air on the backplate, but thats a big lump of metal to heat up with a hot air .
                      When I had lathes with threaded spindles (Oh the joys of D1-3 mounts!) I didn't jam the chucks on tightly, but if I'd been doing work with uneven cuts, like taking the corners off big lumps of square cold rolled, or a lumpy casting, that could wedge them on pretty tightly.

                      Sometimes jamming a piece of softwood between the bull gear and the headstock casting will let you get a stuck chuck off, but then the danger is that you might strip the key.

                      We used to have a rule 'He who puts it on, gets it off again afterwards'
                      'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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                      • #12
                        There's no need for someone to be a gorilla. Remember, as you're machining, the chuck is being tightened onto the spindle.

                        If there was some swarf or dirt on those threads, it could bind that chuck on to a point where it is nearly impossible to get it off. Don't use the back gear to try to lock the spindle - you will break off teeth in this situation. I've had to braze up a 10L back gear and file the teeth back into configuration for someone who had done this. I've seen people make expanding mandrels to try to hold the spindle in position, strap wrenches used on the belt sheaves, etc. Using a good strap wrench is probably your fastest option to hold the spindle. You could clean the spindle with brake cleaner, then use some rosin to make the strap wrench really "grab" the spindle. Then put a piece of bar stock between the jaws and whack it with a dead-blow hammer.

                        I saw a chuck get wedged onto 10L so hard at TSJC that they had to pull the jaws off the chuck and literally machine the chuck off the threads. They used penetrating oil, temperature differentials, strap wrenches, hammers, you name it. They had four experienced machinists and gunsmiths looking at how to get that chuck off for days.

                        They ended up machining the chuck casting off in successive passes until they got to the very top of the threads on the spindle, and then they had to pick what was left out of the thread grooves. They saw where some swarf got pressed into the threads of the spindle.

                        The secret to avoiding this is to a) always clean the threads on a thread-on chuck, and b) use copper anti-seize on the threads.

                        Good luck.

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                        • #13
                          One other method is using the spindles inertia to unscrew the chuck. Rotate the chuck so that a jaw is horizontal to the rear.
                          Cut a piece of wood to fit the space between the jaw and lathe bed. End grain vertical. Slack the belt tension then rotate the chuck
                          by hand smartly against the block. Works every time. Keep the spindle threads and seating face oiled as well as clean.
                          RichD
                          RichD, Canton, GA

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                          • #14
                            If all else fails, what if you (Gasp!) turned a piece in reverse?
                            Put a piece of pipe in the chuck, and a arbor to catch the chuck; arbor in tailstock and steady rest,
                            the arbor may catch the chuck with the ID of the pipe.
                            turn the tool bit upside down and turn in reverse.
                            Has this ever been tried at all? anywhere?

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                            • #15
                              I think that unless you're doing an interrupted cut in reverse it won't make much difference if it's that well stuck on.

                              I'd do a few heating/cooling cycles with penetrant oil first, just as a matter of habit, then make a strap wrench for the back end of the spindle, stick as large a piece of steel hex in the chuck that will fit all the way to the back and use an impact wrench. If you want to get fancy maybe stick some dry ice inside the spindle first.

                              I'm a big fan of heating then using freeze-off several times. Haven't failed to get anything off nor have I busted up any fasteners since I started doing that.

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