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Turning metric threads on an atlas with qcgb?

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  • Turning metric threads on an atlas with qcgb?

    Anyone have a chart or something that shows what combination of gears are needed for different metric threads? More specifically I want to turn 1.5mm pitch. It is very very close to 17tpi which is skipped on the qcgb.

    The charts I am finding on google aren't really "atlas" specific.

    Appreciate any help!
    Andy

  • #2
    Do a search of this site. I just asked this last week and got tons of good info. The short version is, cutting metric threads is completely different and will require you to do some math. And some pitches will require gears you don't have.

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    • #3
      I've got one . Not sure how to post it here. Open to suggestions.
      JIM : You don't get a 2nd chance to make a 1st impression.

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      • #4
        And you can't release the half nuts during the process of cutting the whole thread.
        It's only ink and paper

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        • #5
          Originally posted by vpt
          Anyone have a chart or something that shows what combination of gears are needed for different metric threads? More specifically I want to turn 1.5mm pitch. It is very very close to 17tpi which is skipped on the qcgb.

          The charts I am finding on google aren't really "atlas" specific.

          Appreciate any help!
          Andy,

          I just cut 1.50 threads yesterday on my Atlas for a group of ER collet nuts. You'll need a 40/52 gear cluster in the slot to mate with the QC box. The 52T gear goes to the outside. Mount a 48T next to the reverse tumbler gear and to the inside so it mates with the 32T gear on the tumbler and the 40T on the cluster. Set the QC selector to C-4 and you're good to go.

          A previous contributor reiterated about leaving the halfnuts engaged. I have to psych myself and practice the motions a couple times so I don't automatically disengage. You'll no doubt find a sequence that works for you, but since reversing the motor is noticeably inconvenient on my machine my procedure is this. I'm usually in back gear just so things don't happen too fast and some of my parts are threading to a shoulder so it can get exciting in a hurry. Anyway, with the carriage well clear I turn on the motor for the cut, gauge a stop point to coast into the thread clearance slot (and prepare to snub the chuck if necessary. When stopped I flip the back gear lever to freewheel the spindle, crank the crosslide back with the right hand, crank the spindle in reverse with the left (spindle crank installed), crank crosslide back to zero when clear, advance the compound, re-engage back gear and have at it again.

          As it happens this order for nuts was a fairly short internal thread that had to stop precisely so I hand cranked the whole thing - in and back - and don't mind saying my left arm is a little tired of that.
          .
          "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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          • #6
            The chart I have shows a 48T idler driving a 40T compounded with a 52T. The 52T meshes with the gear in the gearbox. The 32T part of the 16/32T compound is used to drive the 48T idler. So the gear train goes 32-48-40 with the 40T on the same shaft as a 52T, the 52T driving the gearbox. The left gearbox lever is set to C and the right one is set to 4.

            Be sure to check this as errors have been found in some of these charts. It looks like the 40/52 compound should reduce the 22TPI setting thusly: 22 X 40/52 =16.92 TPI which is roughly equal to 1.5MM pitch.

            Edit: Looks like TGTool beat me to the punch!
            Don Young

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            • #7
              Not undoing the half nuts is key. Try the Atlas lathe users group on Yahoo, or look for an Atlas manual from ebay or Clausing.
              gvasale

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              • #8
                If you have a thread dial, with a little practice you can open the half nuts when doing metric threading. You still have to stop and reverse the spindle, though. What you have to do is keep the thread dial on the same number WITHOUT LETTING IT GO AROUND. You open the half nuts and stop the motor at the same time while watching the dial. Then, after backing the tool out, reverse the carriage and spindle while trying to get the dial back to the same position on the same revolution. If you do let it go around you can just adjust the spindle or carriage to make it go back around the other way. Once you have the carriage and spindle suitably positioned, reclose the half nuts while making sure backlash is taken up in the proper direction.

                It may sound complicated and hard to understand, but if you try it a few times without actually cutting anything you will get the hang of it and see that it gives exactly the same results as keeping the half nuts closed. I don't know why this technique is not better known.
                Don Young

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                • #9
                  Andy, the specific reference you need is the Atlas manual entitled "Atlas Quick Change Atttachment Hand Book". Its a 72 page booklet that has thousands of feed gear set-ups, including metric threads and coil winding.
                  My booklet was printed in 1947, with a soft blue cover. If you can find one you will treasure it!
                  Joe B

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                  • #10




                    Hope this is of help.
                    JIM : You don't get a 2nd chance to make a 1st impression.

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                    • #11
                      Originally posted by Carld
                      And you can't release the half nuts during the process of cutting the whole thread.
                      With the right setup, it is perfectly possible to use the half nuts identically as for imperial threads. The secret is to ensure that the re-engagement is with the spindle, lead screw and saddle in EXACTLY the same place, each time you engage.

                      Use a felt tip to mark the headstock & chuck, leadscrew and housing, each with a line, to visually align them each time. Put a block of wood between the front face of the tailstock (locked down) and the back face of the saddle, so the start point for the saddle is always the same. Do this with the clasp nuts engaged. This is critical!! Make your first cut

                      For all subsequent cuts, ensure the chuck/headstock line up at the same time as the leadscew/housing, with the saddle in the start position. The clasp nuts should 'drop-in' cleanly each time..

                      My old (pre-war) Myford has neithe a reversing switch, nor a thread dial, but I can still cut any thread the gears will give, using the casp nuts.

                      NzOldun

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                      • #12
                        If your lathe cannot reverse easily and accurately (mine can't) then using a manual crank handle in the spindle is a perfectly good method. I use this all the time for cutting metric threads on my old Myford and it really takes no more time, unless the thread length is significant. It also allows for very good feel for how the thread is cutting allowing you to gauge the depth of cut you take. Another significant advantage is that threading up to shoulder, even blind internal threads is no problem - you just stop cranking when you touch the shoulder. Sometimes primitive methods are the best. If you would like a picture of the handle that I use (a Geo Thomas design) let me know.
                        Bill

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                        • #13
                          Thanks for the chart Kingweld! I asked a couple places and on another forum (more atlas guys) a PDF was posted that had nearly that same chart in it. I just have to look threw my stack of gears to see if I have the right ones now.

                          The other problem is the reversing. I have a motor that is able to be reversed and a drum switch with reversing capabilities. When I first set up the lathe I wired the switch how I thought it should be wired to reverse the motor. Wire strait on one side of the drum + to + wire - to - wire, on the other side of the drum I reversed the wires tot he motor so it was + to - wire and - to + wire. (110v mind you). But when I tried it the motor spun one way no matter where I turned the switch. Later I found a plate on the motor itself that said to reverse the wires have to switched inside of the motor?

                          Anyone happen to have some info on that deal? I believe it is a dayton 3/4hp 110V motor. I forget the name on my drum switch.
                          Andy

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                          • #14
                            NzOldun, yes, I am aware that can be done but it can get troublesome enough watching the thread dial, backing out the crossfeed, turning in the compound, etc. without adding watching when the chuck and lead screw are timed together and engaging the half nuts. It's much easier to just reverse the spindle.

                            vpt, you may have to use two switches. One to reverse the wires in the motor and another to turn the motor on and off. I had a motor on the Logan I had that was reversible by moving a plate under a cover at the end of the motor. When I wanted to do some reversing I had to expose the plate and shift it for forward or reverse. Since the chuck was a threaded on type I didn't use it in reverse much at all.
                            It's only ink and paper

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                            • #15
                              Thats exactly how mine is. I tore mine apart to figure it out and the inertia switch was sticking a bit so I wanted to clean that up anyhow. What I have figured out is not so much the leads get switched but two of the winding wires get switched to reverse the motor. With my drum switch I have 3 drums and 6 leads. I figured I could run the two winding wires up to the switch and have the switch reverse the winding wire to reverse the motor, then two wires back down tot he motor to tie in with the appropriate winding wires. But it only leaves me with 1 drum and two leads than (which if an electric motor can work like a light bulb?) I can run the hot (+) wire threw the one drum to switch on the motor but then the ground (negative/neutral) would have to be wired direct all the time. Is that ok on an electric motor or should both hot and ground leads be switched/disconnected when not in use?

                              Couple pics, yes its all dirty. The motor is a 1/2hp not 3/4 like I thought before. Split phase.









                              More pics next post.
                              Andy

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