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  • Turning left handed threads

    I have a feeling i know this answer.

    The drive shaft on my weed wacker broke. I can get a new one for $40, so no issue there. But, I'm here with this snazzy lathe on my bench. So I'm thinking, why couldn't I just fix this. The shaft broke right at where the threaded arbor comes out. So I think, I could face that, drill and tap it, then thread in a new arbor and locktite it in. Then I have the threaded part protruding the correct amount to attach the spool. Then I hit my snag, the arbor is left hand thread, so the nut doesn't come off during operation. I have no left handed dies. My Atlas lathe doesn't have reverse, and it's threaded chuck would prevent me from threading in reverse anyhow. So, is there another way to turn left handed threads?

  • #2
    Sure you can cut left handed threads. Reverse the direction of the lead screw,not the chuck,to make left handed threads

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    • #3
      Originally posted by Andrew S. Quinn
      Sure you can cut left handed threads. Reverse the direction of the lead screw,not the chuck,to make left handed threads
      and the direction you swing the compound (30 degrees to the left of sq to the axis) to cut on the slant depth (rather than straight depth)

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      • #4
        Are you sure you need left handed threads? I haven't run my weed eater yet this year so I'm just going from memory, but I think right handed will tighten during use.

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        • #5
          The spindle's nut is LH on mine.

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          • #6
            Keep in mind, If the original one broke, and you plan to make a stud to thread in to the broken one, the diameter will be smaller and weaker, not be heat treated, and likely break easier. Maybe money well spent on a new one, or making a whole new piece and probably heat treat it. Not to me a buzz kill, just a reality check.

            ---Doozer
            DZER

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            • #7
              Originally posted by Doozer
              Keep in mind, If the original one broke, and you plan to make a stud to thread in to the broken one, the diameter will be smaller and weaker, not be heat treated, and likely break easier. Maybe money well spent on a new one, or making a whole new piece and probably heat treat it. Not to me a buzz kill, just a reality check.

              ---Doozer

              Thanks all. It didn't occur to me that left handed threads were made by reversing the lead screw, I assumed the chuck had to reverse. Duh. And yes, I'm dead positive it's left handed threads.

              Doozer, I plan to use the same size stud that's in there now. I'm planning to face it off flat and drill and tap it the same size as it is now. It didn't break from use. It broke when the person trying to change the spool didn't realize it was left handed threads and put a big old grunt on the wrench. The nut is plastic with an aluminum insert, so I have to assume unheat treated steel would suffice. The steel doesn't seem hardened I any way, a file takes a nice easy cut right through it. But I'm open to suggestion. If you gets think its a bad idea, I'll pony up the dough. I'm not being cheap, I just like making stuff. ;-)

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              • #8
                You have a lathe and have to ask??? :-) Make it!!!!!
                ...Lew...

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                • #9
                  Originally posted by nitsuj
                  Thanks all. It didn't occur to me that left handed threads were made by reversing the lead screw, I assumed the chuck had to reverse.
                  You need to reverse the lead screw relative to the chuck no matter what, but you can also reverse the chuck. If your chuck is threaded on then you might get a surprise when it goes walking across your shop floor, but it will work if the chuck stays in place. This will allow you to thread from the back side of the apron where setting the 29.5؛ offset will be easier to do.

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                  • #10
                    Go ahead and make it. Sounds like it should work.
                    It's only ink and paper

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                    • #11
                      Originally posted by dp
                      You need to reverse the lead screw relative to the chuck no matter what, but you can also reverse the chuck. If your chuck is threaded on then you might get a surprise when it goes walking across your shop floor, but it will work if the chuck stays in place. This will allow you to thread from the back side of the apron where setting the 29.5؛ offset will be easier to do.
                      And don't forget to put the tool upside down, or put it in backwards when using reverse!

                      (I will let you think about that one for awhile...)
                      Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                      • #12
                        Originally posted by Andrew S. Quinn
                        Sure you can cut left handed threads. Reverse the direction of the lead screw,not the chuck,to make left handed threads
                        Isn't it just easier to stand on your head and cut the thread in the regular manor.
                        The shortest distance between two points is a circle of infinite diameter.

                        Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

                        Southwestern Ontario. Canada

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                        • #13
                          Originally posted by loose nut
                          Isn't it just easier to stand on your head and cut the thread in the regular manor.
                          Try it,and then get back to us with your thoughts on that !!

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                          • #14
                            Said in a different way.
                            Just start at the shoulder and thread away from the headstock. This produces left handed threads.

                            You can really crank up the rpm's if you want, because there is no danger in crashing into the shoulder.

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