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  • Embarrassing newbie lathe crash

    I should begin by introducing myself.....Troy near Houston, Texas.

    I've been lurking around here for quite a while and recently picked up a Select Machine Tool 12x24 lathe. Being that I have only seen some one operate a lathe, I have A LOT to learn.

    Long story short, I auto fed the carriage as far as possible toward the chuck. The result is a broken gear in the QC gearbox and the carriage is stuck. The lever to engage the auto feed is also stuck....in gear.

    So, I'm looking for advice on how to un-stick the carriage. My first thought is to figure out how to turn the leadscrew in the opposite direction to "unscrew" the carriage. I've grabbed the end of the leadscrew and applied a minimal amount of force, but it's not budging.

    Thanks for any input.

    Troy

  • #2
    Have you tried turning the spindle/chuck backwards, probably by hand?

    If there is a gear broken in the QC gearbox this may not work but it probably won't make it worse if you don't lean on it too hard.

    Dave

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    • #3
      The broken gear in the QC gearbox eliminates that idea. I had the same thought when it happened, that's how I found the broken gear.

      Troy

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      • #4
        Dismantle the carridge. Take the QC to pieces if you have to get the lead screw disconnected, but it may be as simple as removing the shear pin. Take a lot of pics...

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        • #5
          IF nothing hit the chuck and the chuck is not threaded on the spindle you should be able to bend a bar 90 deg and stick the short end in the chuck and snug the jaws with the long end laying against one jaw. Then you can use that to turn the spindle the opposite direction it was going when it locked up. As your trying to turn the chuck apply pressure to release the power feed lever. It may take a lot of effort but that's the easiest way I have found to do it.
          It's only ink and paper

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          • #6
            I fixed it. Apparently, when the carriage is fed to its limit toward the chuck there is a small portion of the apron that contacts a "sleeve" on that end of the leadscrew. The sleeve has something to do with supporting the leadscrew in that area.

            The power feed ran the apron into the sleeve, the leadscrew continued to turn wedging the apron into the sleeve. When it couldn't wedge any tighter the QC gear broke. A firm grip on the OD of the sleeve with a pair of channel locks was all it took to turn the leadscrew backward and push the carriage toward the tailstock. Once it started moving the half nut was easily disengaged.

            All is well now except for some slop in the carriage, a broken QC gear and a broken back gear. I'll save those for another thread.

            Thanks for the input!

            Troy

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            • #7
              Best lessons are learned on your own. Someone just telling you to watch out for going to far with the carriage wouldn't leave a lasting impression as actually doing it.
              Andy

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              • #8
                Originally posted by vpt
                Best lessons are learned on your own. Someone just telling you to watch out for going to far with the carriage wouldn't leave a lasting impression as actually doing it.

                I don't think they are the BEST lessons but certainly they leave the biggest impression.

                For me the best lesson would be for someone to explain what could happen if I ran the carriage too far and what I might break or get ruined in the process.
                Location: The Black Forest in Germany

                How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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                • #9
                  Experience is a great teacher, but she can be a ruthless b&%#*, sometimes.
                  I cut it twice, and it's still too short!
                  Scott

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                  • #10
                    i would have thought that such a lathe would have had an overload device built into them ..

                    either it clicks itself off the feed or bust a shear pin in the gear train ..

                    also you can fit a micrometer carrage stop ..looks like this



                    all the best.markj

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                    • #11
                      Halfnuts?

                      [the leadscrew backward and push the carriage toward the tailstock. Once it started moving the half nut was easily disengaged. ]

                      So were you threading when this happened, or does your lathe use leadscrew and half nuts for turning as well as threading? I inherited an old hercus that the previous owner used the half nuts for regular turning as they apparently didn't understand how to use the feed (which has a clutch and a shear pin).

                      I realize the damage is done, just wanted to make you aware there's a difference for automatic feed or threading. Using the leadscrew instead of the feed rod makes for some nasty crashes!
                      I spent most of my money on women and booze, the rest I just wasted.

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                      • #12
                        completely unrelated but reminds me of a story one of the old timers in this
                        town likes to tell every now and again.

                        as it goes, when he was "just a lad" .. "about that age where a boy becomes
                        a man and needs to know things like where his land ends and another man's
                        begins".. his father took him out one afternoon and they surveyed all of their
                        property.

                        his father showed him all the land they owned, explained what they'd planted there
                        in the past, and who their neighbors where.

                        In one particularly overgrown corner of a certain plot, over some rough
                        terrain and through thistles, they arrived at a small clearing otherwise
                        impossible to find if not led there.

                        his dad looked him straight in the eyes and out of nowhere SLAP, the
                        smartest backhand he'd ever felt, clean across his face.

                        he said "son, your grandfather showed me this same exact spot, this
                        same exact way, and to this day, I'll never forget where this place is"

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                        • #13
                          Originally posted by The Fixer
                          the previous owner used the half nuts for regular turning as they apparently didn't understand how to use the feed (which has a clutch and a shear pin).
                          Unfortunately this is where I fit in! After reading your post, and doing some thorough research(ie. reading the manual) I now have somewhat of an understanding of how the feedscrew works. Once the replacement gear arrives and I get the QC back together I will give it a shot.

                          I like this thing! My thick skull is costing me a little along the way, but I'll get the hang of it.

                          Troy

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                          • #14
                            Learning Curve

                            That's just the way it is. You have to pay for your education one way or another. For example: College tuition, lost time, lost money, broken parts, etc. Experience is what you get right after you need it. All you can do is learn the lesson, pay the dues and move forward.
                            Last edited by Toolguy; 12-28-2011, 08:01 PM.
                            Kansas City area

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