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Lathe gears - how loose ?

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  • Lathe gears - how loose ?

    How loose, how tight should one keep the gears on the outboard gear train? i.e., the adjustable gearing between the QC gear box and the gears from the spindle.

    I recently cleaned, greased, and adjusted the gears a bit snugger than before and performance is fine, but noise is markedly more egg-beater noisy, like a sports car in reverse. Before it was more like Casey Jones' choo-choo train chugging along.

    Opinions requested in regards to performance, wear and noise, and any other issues of importance.


    Appearance is Everything...

  • #2
    You need a little clearance. Put in a piece of paper when adjusting them "snug", then remove the paper - it will be about right.


    • #3
      Thank you Lakeside. Yes, I have re-adjusted them and they are noticeably quieter. I also notice those (3) gears I had tightened weren't holding any grease, more of a polished appearance than the other gears. The lathe is sounding as it did in the past.

      Appearance is Everything...


      • #4
        I use the paper method too & it's worked for me also.
        "Let me recommend the best medicine in the
        world: a long journey, at a mild season, through a pleasant
        country, in easy stages."
        ~ James Madison


        • #5
          How thick is your paper??


          • #6
            Traditionally, you used a cigarette paper, which were also popular for edge finding. Stick it to the work with a lick of saliva, then bring the tool up till it grabbed the paper.

            Of course, they come in a range of thicknesses, down to 20 micron in same cases.
            Paul Compton


            • #7
              Use a Dollar bill. It's a little thicker than cig paper, but tougher.



              • #8
                I tend to blue it and move the tool til it comes off, I'm not sure if I'm doing it right as I'm mostly self taught anyway and I've got a crappy teacher, lol
                Rizlas work too
                I wish I hadn't rolled so many cigs


                • #9
                  This will vary somewhat with different lathes and the gear pitch. The involute gear form is somewhat tolerant to the spacing and that leads me to believe that a bit over is better than too little. If there is insufficient space, then they will make more noise and that probably means more wear.

                  I use card stock, as used for index cards or it can be purchased in full 8.5 x 11 sheets and probably larger. A narrow strip, about the width of the gear face, is best as it will conform to the gear shape easier. If I use paper, I double it. Sometimes, for a quick threading operation I just wing it: I jam them tight and then move one out just a bit. This seems to work for me as my fingers have been "calibrated" for it after many such set-ups.

                  Good lubrication is important. There are oils made for use on gear teeth and these are probably the best. I often use way oil as it has good stiction so it stays put. Keep the hubs well lubricated too. I purchased two compound gears with their own mounting hubs. The holes in the gears were work at least 1/32" larger in diameter from constant use and wear, probably without lubrication. I had to bore larger holes and make larger hubs for them. A manual lathe should be lubricated each day it is used. Make a chart so you do not miss any of the lube points.

                  My SB9 has a tumbler reverse and I always put it in a central or neutral position when I am not using the gearing for threading or feeds. This should help to minimize further wear on the gear teeth and hubs. One day I mean to make a three position lever with detents for this operation.
                  Paul A.

                  Make it fit.
                  You can't win and there is a penalty for trying!


                  • #10
                    The lube part is interesting. Mine have been bone dry for seven years. What is the correct procedure here.?


                    • #11
                      Anyone who can adjust gears to the thickness of a bit of paper must have a brand new lathe. With my old stoker - a Colchester Bantam - I tighten up the gears, hold one gear and jiggle the mating gear to feel for play, and if there's a little play I leave it. No play, or too much play - do it again.

                      Then, when I put the power on, I listen. If anything is too tight I can hear a regular grumble from the gears.

                      I figure a little too much play can't do any harm. There's so much backlash in various parts of the gear train that a little more makes little difference.
                      Richard - SW London, UK, EU.


                      • #12
                        Originally posted by plunger View Post
                        The lube part is interesting. Mine have been bone dry for seven years. What is the correct procedure here.?
                        -Get some "Open Gear Lube". Most decent auto parts stores should have it, or you might have to order some. It's a sticky, waxy spray- the stuff I have says to spray it on, and wait 20 minutes or so before using the machine. Time for the carriers to evaporate a bit, I presume.

                        Quieted my geartrain down significantly. It's messy, and like any lube needs to be periodically reapplied, but it works.

                        Only drawback is that I tend to get afraid that dust and fine swarf will get embedded in the goop, but I've just taken to periodic cleaning (with solvent) and reapplying.

                        Doc's Machine. (Probably not what you expect.)


                        • #13
                          Way oil is also an excellent open gear lube. It is used expressly for that purpose in the printing industry. It stays on the gears and does not attract dust and other contaminants. I give my end gears, apron and QCGB a shot about once a week.
                          Jim H.


                          • #14
                            All of this "paper" and anything else similar presumes that there is no wear on the involute faces of the gears. The real spacing of course will be (original spacing + wear (to compensate for wear)).

                            But the "cigarette paper" thickness will be OK in just about all situations (other than severe wear).

                            Needless to say as gears are changed around over time there will be variations between different gear combinations in the amount of wear.

                            Machinery's Hand Book covers this situation very well.

                            This is a classic "rule of thumb" situation which mostly (not always) works but many "rules of thumb" as not quite so accurate or accommodating so care and caution are needed.



                            • #15
                              If there is a truck stop near you, get a spray can of 5th wheel and slider lube. Spray it on and let the carrier evaporate. It's leaves a coating about 1/32" thick which is not messy and not supposed to attract dust and grit.

                              I know it will make the sliders work easier when you need to adjust the wheelbase on a trailer.