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Did a little single point threading today

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  • Did a little single point threading today

    I'm staying at my parents in the mountains while I build a home. I needed a good brush cutter to clear some property so I got a Grass Gator to use on my Dad's Shindiawa T-27 straight shaft weed eater. The problem is that the kit didn't come with the 8 MM 1.25 Left Hand Thread shoulder bolt necessary to adapt it to this machine. So...
    Using my Dad's Atlas 10" lathe with Plain Change gears and the Atlas Gear Chart I geared the machine to 1.25 TPI, Got an old 3/8" Grade 5 bolt for stock, drilled a center in the threaded end, held the hex end in the 3 jaw chuck and shimmed until it ran true, turned relief at each end to the minor diameter for an 8 MM 1.25 thread, set the machine up, compound swung to the left 29 degrees, threading tool centered and squared with fishtail gauge, lead screw to move carriage away from headstock, second to slowest speed in back gear. I used Tap Magic for cutting lube.

    Here's the result:

    This is my first attempt at LH threading and first Metric on an Atlas lathe using their recommended transposing setup. For Atlas owners wondering if the 1:3000 error in the setup matters, it didn't in this case. Everything went together like it was factory made.

  • #2
    Success tells it all. If you bought it you would still not know if you could do it. Stick out you chest and crow about it.


    • #3
      And some people say Atlas lathes are junk. Good job.


      • #4
        Good looking work! Since 1 in 3000 is about equal to 0.0003" error in 1", that is accurate enough for a pretty decent micrometer so it should do for a bolt!

        I spent most of my working career in metrology and calibrating precision instruments and I can tell you that the only thing that can be without error is counting and related mathematics. You can count teeth on gears exactly but you can't ever cut an exact thread pitch. We used to say 'All measurements are wrong. It's good to have some idea as to how much.'
        Don Young


        • #5
          Good Job.
          I think left hand threads are easier than right hand threads, because you are threading away from the headstock.
          Ever priced a left hand socket head cap screw? (1/4-20) About $7 each


          • #6
            Good for you.

            In machining I always feel there are way points that once you have passed you are one step nearer to feeling your experience.
            Others may have different views on this but I feel Parting off, single point threading and gear cutting form major milestones

            Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.


            • #7
              Thanks for the kudos guys. It's especially appreciated from accomplished machinists like yourselves. I've done some single point RH threading at home on my Logan with QC gearbox and even some metric with proper transposing gears, but never LH on a lathe not all that familiar to me using plain change gears and a setup that approximates the pitch. As Don Young pointed out, an error that small is insignificant in most cases.

              Although this little project was not big or exciting for most experienced people here, I hoped it would provide encouragement to other non professional self taught "wannabees" like myself. In the past I've read questions by other Forum members about metric threading on the Atlas machines using their suggested gear arrangements. Hopefully this post will be reassuring to those folks should they still be wondering about feasibility.

              Sir John, so far I've been successful with both parting and threading. Gear cutting is next on the list when the opportunity presents itself. Personally, I found parting to be the most difficult to accomplish and threading to be a breeze with success at the first attempt. After a lot of reading, thinking, study and trial and error parting came to be easy as well.
              Last edited by firbikrhd1; 12-09-2012, 09:59 AM.