Announcement

Collapse
No announcement yet.

Need a Leadscrew, But from which Lathe?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Need a Leadscrew, But from which Lathe?

    I'm going to convert the lead screws on my 9x20 to something more sensible. The originals are 3/4-16 for the carriage and 9/16-20 for the cross slide. I want to go to 3/4-8 for the carriage and 1/2-10 for the cross slide. Cross slide is easy, already have a 1/2-10 LH Acme tap.

    The one for the carriage I'm looking to pick up a used leadscrew off Ebay and modify it to work, rather than buy a section of leadscrew and then have to mill a long key slot in it. So the question is, what lathes used a 3/4-8 lead screw? Atlas, SB, Logan?
    I just need one more tool,just one!

  • #2
    I believe the Atlas 12 x 24 we are working on at the moment has a 3/4" x 8 leadscrew with a longitudinal slot, but I won't be able to confirm that till Wednesday.

    Comment


    • #3
      Curious what exactly bothers you enough to go to the trouble to do this?
      "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

      Comment


      • #4
        Rockwell 10" does. I believe south bends did too.
        21" Royersford Excelsior CamelBack Drillpress Restoration
        1943 Sidney 16x54 Lathe Restoration

        Comment


        • #5
          Originally posted by mickeyf View Post
          Curious what exactly bothers you enough to go to the trouble to do this?
          If you do much threading, the 16 tpi half nuts get sloppy fast, it's also easier to miss timing on the halfnut. I also need to cut pitches coarser than the 8 tpi that comes standard. I could do that with gearing, but cutting 8 tpi already has the leadscrew running so fast it starts to whip at anything over 30 rpm on the spindle.

          Changing it isn't that difficult, some turning on each end of the leadscrew and a new set of half nuts is all.

          The cross slide screw will yield better parting and a direct reading dial. I also am planning a mod that will give me power cross feed.
          I just need one more tool,just one!

          Comment


          • #6
            I just serviced a couple Bulldog side winder implement jacks last night they look to be about 3/4" acme,not sure on pitch might be worth checking out have got the odd one from metal pile at dump.

            Comment


            • #7
              If you change the leadscrew from 16tpi to 8tpi you'll double the load on the screwcutting gear train. 8TPI is already quite coarse for a 9x20 lathe without stressing the gear train more.
              Peter - novice home machinist, modern motorcycle enthusiast.

              Denford Viceroy 280 Synchro (11 x 24)
              Herbert 0V adapted to R8 by 'Sir John'.
              Monarch 10EE 1942

              Comment


              • #8
                South Bend 9" uses 3/4-8 RH, however it is cheaper to buy the threaded rod stock from McMaster

                Comment


                • #9
                  Originally posted by Peter. View Post
                  If you change the leadscrew from 16tpi to 8tpi you'll double the load on the screwcutting gear train. 8TPI is already quite coarse for a 9x20 lathe without stressing the gear train more.
                  I won't be threadeding steel or stainless in those pitches,I can do that at work much faster. I make some parts and pieces in Delrin and UHMW that need a 4 pitch, that should be attainable on the 9x20
                  I just need one more tool,just one!

                  Comment


                  • #10
                    Originally posted by nickel-city-fab View Post
                    South Bend 9" uses 3/4-8 RH, however it is cheaper to buy the threaded rod stock from McMaster
                    It may come to that, I did find a couple Atlas ones on Fleabay for cheap. I'm trying to avoid milling the slot, it wouldn't be difficult to do it, but with rolled thread leadscrew material it's hard to know for sure what the stress is going to do. It might stay straight, or it might corkscrew.
                    I just need one more tool,just one!

                    Comment


                    • #11
                      Originally posted by wierdscience View Post

                      It may come to that, I did find a couple Atlas ones on Fleabay for cheap. I'm trying to avoid milling the slot, it wouldn't be difficult to do it, but with rolled thread leadscrew material it's hard to know for sure what the stress is going to do. It might stay straight, or it might corkscrew.
                      I doubt there would be much stress in a low carbon steel but you're right it could still be a factor -- could always bury it in a charcoal fire overnight before machining if you were really worried about it. I do know that SB parts will have high prices, and be worn out already.

                      One alternative may be to go to Grizzly and order a replacement new lead screw for the current Heavy 10 model -- not gonna be cheap tho.

                      Comment


                      • #12
                        Originally posted by nickel-city-fab View Post

                        I doubt there would be much stress in a low carbon steel but you're right it could still be a factor -- could always bury it in a charcoal fire overnight before machining if you were really worried about it. I do know that SB parts will have high prices, and be worn out already.

                        One alternative may be to go to Grizzly and order a replacement new lead screw for the current Heavy 10 model -- not gonna be cheap tho.
                        It is a factor. A fellow on PM shaped a slot on his planer for a new rod and it bowed big time. He had a process for straightening it. I'll try to find the thread if there's interest.

                        wierdscience, how do you intend to re-do the halfnuts? Bore out and recast with babbitt?
                        21" Royersford Excelsior CamelBack Drillpress Restoration
                        1943 Sidney 16x54 Lathe Restoration

                        Comment


                        • #13
                          Originally posted by The Metal Butcher View Post

                          It is a factor. A fellow on PM shaped a slot on his planer for a new rod and it bowed big time. He had a process for straightening it. I'll try to find the thread if there's interest.

                          wierdscience, how do you intend to re-do the halfnuts? Bore out and recast with babbitt?
                          Take two blocks of Bronze, stick them together with solder, bore and thread then machine off everything that doesn't look like a halfnut pair. These things are pretty simple little half nuts, no cast iron involved.
                          I just need one more tool,just one!

                          Comment


                          • #14
                            All of the above (Atlas, Logan, SB), and others.

                            Would you actually need the slot? The McMaster rod has a pretty large error per foot in pitch, as I recall.
                            1601

                            Keep eye on ball.
                            Hashim Khan

                            Comment


                            • #15
                              Try out your ACME tap on something soft before using it on bronze.

                              Comment

                              Working...
                              X