Announcement

Collapse
No announcement yet.

change gears?

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

  • change gears?

    Where can I go to find/learn about change gears? Is there any general rules of thumb or info available? I had someone give me an old lathe with a box of change gears. His father used the lathe and he has no clue. It is an old Ariston lathe. Metric only. The only thing I know is that I don't know anything about making threads!
    Location: The Black Forest in Germany

    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

  • #2
    There is a book in the "Workshop Practice" series, by Matin Cleave called "Threading in the Lathe". It is probably as good a source of information on the use of change gears, as you will find.

    Comment


    • #3
      The old standby is the South Bend book, "How to Run a Lathe." But I think the Atlas (Craftsman) book "Manual of Lathe Operation and Machinists Tables" gives a clearer explanation of change gears and threading operations.

      Check eBay and/or Amazon.

      Comment


      • #4
        Originally posted by Black Forest
        Where can I go to find/learn about change gears? Is there any general rules of thumb or info available? ... It is an old Ariston lathe. Metric only.
        The 'Screw-cutting in the lathe' book by Martin Cleeve (as already suggested but this time with slightly better spelling) is excellent.

        Starting from the basics, you need to determine the pitch of your leadscrew. Easiest way to work this out is to engage the half-nuts and measure how far the carriage moves for one (or ten) turns of the leadscrew. This will be a 'sensible' number of millimetres if, as you say, the lathe is metric.

        If you then gear the spindle to the leadscrew with a 1:1 ratio, this is the pitch of thread you will cut.

        If you want a coarser thread (unlikely as leadscrews are generally pretty coarse already but we'll do the exercise anyway), you have to change the ratio of the gearing so the carriage moves further/faster for one spindle revolution. In other words, for one rev. of the spindle, the leadscrew must make greater than one rev. Hence you have to gear it up (bigger gear on the spindle, smaller gear on the leadscrew).

        If you want a fine thread, you have to slow down the carriage so it moves less/slower. For one rev. of the spindle, the leadscrew must turn less than one rev., hence you have to gear it down (small gear on spindle, large gear on leadscrew).

        Working out the gear ratios requires nothing more than a high school level of familiarity with fractions.

        Comment


        • #5
          Thank you for the answers. I will buy the books suggested. Anymore info offered would be appreciated.
          Location: The Black Forest in Germany

          How to become a millionaire: Start out with 10 million and take up machining as a hobby!

          Comment


          • #6
            Any help?

            Originally posted by Black Forest
            Where can I go to find/learn about change gears? Is there any general rules of thumb or info available? I had someone give me an old lathe with a box of change gears. His father used the lathe and he has no clue. It is an old Ariston lathe. Metric only. The only thing I know is that I don't know anything about making threads!
            BF.

            This should help. It is from a Technical and Further Education (TAFE) Department in one of our Universities of Technology in Australia (OZ) and as OZ is a metric country it is predominantly metric.

            It may seem like "heavy going" but its not really as all the basics and fundamentals are there.

            Just take it slowly and steadily and you will be OK.

            If I can be of any further help, please don't hesitate to ask and I will do what I can to assist.

            Part 1 (Chapter 14):
            http://i200.photobucket.com/albums/a...w_threads1.jpg

            http://i200.photobucket.com/albums/a...w_threads2.jpg

            http://i200.photobucket.com/albums/a...w_threads3.jpg

            http://i200.photobucket.com/albums/a...w_threads4.jpg

            http://i200.photobucket.com/albums/a...w_threads5.jpg

            http://i200.photobucket.com/albums/a...w_threads6.jpg

            http://i200.photobucket.com/albums/a...w_threads7.jpg

            http://i200.photobucket.com/albums/a...w_threads8.jpg



            Part 2 (Chapter 29):
            http://i200.photobucket.com/albums/a...d-cutting1.jpg

            http://i200.photobucket.com/albums/a...d-cutting2.jpg

            http://i200.photobucket.com/albums/a...d-cutting3.jpg

            http://i200.photobucket.com/albums/a...d-cutting4.jpg

            http://i200.photobucket.com/albums/a...d-cutting5.jpg

            http://i200.photobucket.com/albums/a...d-cutting6.jpg

            http://i200.photobucket.com/albums/a...d-cutting7.jpg

            http://i200.photobucket.com/albums/a...d-cutting8.jpg

            http://i200.photobucket.com/albums/a...d-cutting9.jpg

            http://i200.photobucket.com/albums/a...-cutting10.jpg

            http://i200.photobucket.com/albums/a...-cutting11.jpg

            http://i200.photobucket.com/albums/a...-cutting12.jpg

            http://i200.photobucket.com/albums/a...-cutting13.jpg

            http://i200.photobucket.com/albums/a...-cutting14.jpg

            http://i200.photobucket.com/albums/a...-cutting15.jpg

            http://i200.photobucket.com/albums/a...-cutting16.jpg

            http://i200.photobucket.com/albums/a...-cutting17.jpg

            http://i200.photobucket.com/albums/a...-cutting18.jpg

            http://i200.photobucket.com/albums/a...-cutting19.jpg

            http://i200.photobucket.com/albums/a...-cutting20.jpg

            Comment


            • #7
              Originally posted by Black Forest
              Where can I go to find/learn about change gears? Is there any general rules of thumb or info available? I had someone give me an old lathe with a box of change gears. His father used the lathe and he has no clue. It is an old Ariston lathe. Metric only. The only thing I know is that I don't know anything about making threads!
              Change gears can be pretty simple for an imperial only or a metric only lathe with a clean design but can get a bit more complicated for machines that try to cut both or that try to get by with too few gears and need more complicated setups, or use weird leadscrew pitches, etc.

              When you mesh two gears, the driven gear turns at the speed of the driven gear multiplied by the number of teeth on the driving gear and divided by the number of teeth on the driven gear, but in the opposite direction. If you insert an idler gear between them, the ratio doesn't change but the direction of rotation is reversed. If you insert a pair of gears coupled together on the same axle, with one meshing with the driving gear and the other meshing with the driven gear, then the ratio of the number of teeth on the two new gears affects the results.

              You should have at least three axles on which to mount gears. One on the spindle or the output of the tumbler reverse or coupled directly to the spindle with a fixed gear (that isn't changed because the spacing isn't adjustable). One on the lead screw. And one on a "banjo" which is a part that pivots around some point and has a long slot; between these two degrees of freedom, you can move the axle so the gear(s) on it mesh properly with the others. Each axle (with possibly one exception), should have the ability to mount 2 gears or 1 gear and a spacer the width of the gears. You may have additional axles, as well, to permit more complicated gear ratios.

              Assuming the first gear connects directly to the spindle or on an axle that rotates once per spindle revolution, then basically compute the ratio of the thread pitch/lead you want to the one on the lead screw and choose a combination of gears with the same ratio.

              Simple gearing:

              (spindle gear) (idler gear) (leadscrew gear)
              spindle gear drives idler gear which, in turn, drives the lead screw gear.
              ratio = spindle_gear/leadscrew_gear

              Example:
              Leadscrew: 1mm pitch
              Desired pitch: 2mm pitch
              ratio 2:1 (two leadscrew revolutions per spindle revolution)
              Spindle gear: 40 tooth (for example)
              Leadscrew gear: 20 tooth (half as many teeth as spindle gear)
              Idler gear: any gear which will fit and allow you to mesh with the two important gears.
              You could also use 32/16, 60/30, 72/36, 36/18
              Swap the two gears, and you will get 0.5mm pitch.

              If you can't find a simple gearing combination which works, you have to resort to compound gearing:
              Code:
              Spindle             Leadscrew 
                 |        |          |
              [GEAR A] [GEAR B]      |
                 |        |          |
                       [GEAR C]  [GEAR D]
                          |
              
              Ratio: A/B*C/D
              Here, gears B and C are on the same axle and keyed to rotate together. Spindle turns gear A, Gear A drives Gear B, C shares an axle with B so it turns at the same rate, and gear C drives gear D. The middle axle turns at a rate of A/B times the rate of the spindle and the leadscrew turns at a rate of C/D times the middle axle, or A/B*C/D times the spindle. If need be, you can insert any gear as an idler between gears A and B or gears C and D and it doesn't have any effect on the ratio other than reversing the direction of rotation.

              For really complicated ratios, you bring a 4th axle into play.

              It is easy to get confused and make your ratios upside down making a finer pitch when you wanted a coarser one, or vice versa, but easily fixed by swapping gears.

              If you have a 127 tooth gear, you should be able to cut exact imperial sizes; if you don't you may be able to get a close enough approximation good for short threads using some pretty weird gear ratios.

              If your lead screw is a sensible pitch related to other standard metric pitches by a simple ratio, your gear setups should be fairly simple. If they used one of the weirder sizes, it gets more complicated. In some cases you can setup one combination of gears that converts that pitch to a more reasonable starting point and leave that setup for most uses and just add other gears.

              There will often by multiple gear combinations that will work, though some might not physically fit due to something getting in the way.

              Here is an example of simple gear combinations with a 1mm lead screw and a few random gear sizes (12, 16, 18, 28, 30, 32, 36, and 48 teeth)
              Code:
              	1mm*12/12 = 1 mm
              	1mm*12/16 = 0.75 mm
              	1mm*12/18 = 0.66666667 mm
              	1mm*12/28 = 0.42857143 mm
              	1mm*12/30 = 0.4 mm
              	1mm*12/32 = 0.375 mm
              	1mm*12/36 = 0.33333333 mm
              	1mm*12/48 = 0.25 mm
              	1mm*16/12 = 1.3333333 mm
              	1mm*16/16 = 1 mm
              	1mm*16/18 = 0.88888889 mm
              	1mm*16/28 = 0.57142857 mm
              	1mm*16/30 = 0.53333333 mm
              	1mm*16/32 = 0.5 mm
              	1mm*16/36 = 0.44444444 mm
              	1mm*16/48 = 0.33333333 mm
              	1mm*18/12 = 1.5 mm
              	1mm*18/16 = 1.125 mm
              	1mm*18/18 = 1 mm
              	1mm*18/28 = 0.64285714 mm
              	1mm*18/30 = 0.6 mm
              	1mm*18/32 = 0.5625 mm
              	1mm*18/36 = 0.5 mm
              	1mm*18/48 = 0.375 mm
              	1mm*28/12 = 2.3333333 mm
              	1mm*28/16 = 1.75 mm
              	1mm*28/18 = 1.5555556 mm
              	1mm*28/28 = 1 mm
              	1mm*28/30 = 0.93333333 mm
              	1mm*28/32 = 0.875 mm
              	1mm*28/36 = 0.77777778 mm
              	1mm*28/48 = 0.58333333 mm
              	1mm*30/12 = 2.5 mm
              	1mm*30/16 = 1.875 mm
              	1mm*30/18 = 1.6666667 mm
              	1mm*30/28 = 1.0714286 mm
              	1mm*30/30 = 1 mm
              	1mm*30/32 = 0.9375 mm
              	1mm*30/36 = 0.83333333 mm
              	1mm*30/48 = 0.625 mm
              	1mm*32/12 = 2.6666667 mm
              	1mm*32/16 = 2 mm
              	1mm*32/18 = 1.7777778 mm
              	1mm*32/28 = 1.1428571 mm
              	1mm*32/30 = 1.0666667 mm
              	1mm*32/32 = 1 mm
              	1mm*32/36 = 0.88888889 mm
              	1mm*32/48 = 0.66666667 mm
              	1mm*36/12 = 3 mm
              	1mm*36/16 = 2.25 mm
              	1mm*36/18 = 2 mm
              	1mm*36/28 = 1.2857143 mm
              	1mm*36/30 = 1.2 mm
              	1mm*36/32 = 1.125 mm
              	1mm*36/36 = 1 mm
              	1mm*36/48 = 0.75 mm
              	1mm*48/12 = 4 mm
              	1mm*48/16 = 3 mm
              	1mm*48/18 = 2.6666667 mm
              	1mm*48/28 = 1.7142857 mm
              	1mm*48/30 = 1.6 mm
              	1mm*48/32 = 1.5 mm
              	1mm*48/36 = 1.3333333 mm
              	1mm*48/48 = 1 mm
              And here are a few examples of 4 gear compound combinations which would give inch threads (A/B*C/D):
              Code:
              	1/(1mm*12/12*127/30) = 6 * 1/inch
              	1/(1mm*12/16*127/30) = 8 * 1/inch
              	1/(1mm*12/18*127/30) = 9 * 1/inch
              	1/(1mm*12/28*127/30) = 14 * 1/inch
              	1/(1mm*12/30*127/30) = 15 * 1/inch
              	1/(1mm*12/30*127/32) = 16 * 1/inch
              	1/(1mm*12/30*127/36) = 18 * 1/inch
              	1/(1mm*12/30*127/48) = 24 * 1/inch
              	1/(1mm*16/30*127/32) = 12 * 1/inch
              	1/(1mm*18/12*127/30) = 4 * 1/inch
              	1/(1mm*18/30*127/30) = 10 * 1/inch
              	1/(1mm*32/16*127/30) = 3 * 1/inch
              	1/(1mm*32/30*127/48) = 9 * 1/inch
              	1/(1mm*36/12*127/30) = 2 * 1/inch
              	1/(1mm*36/18*127/30) = 3 * 1/inch
              	1/(1mm*36/30*127/30) = 5 * 1/inch
              [NOT APPLICABLE] If you have one special gear which mounts on the spindle which isn't interchangable with the other gears (different hole size), your gear settups get a little more complex. If you have a change gear with the same number of teeth as the special gear, try mounting that one on the lead screw and then you may be able to do most thread setups by just stacking two gears on the same axle with the ratio you desire.

              [NOT APPLICABLE] If you do not have a tumbler reverse, you change between left and right hand threads by either adding or subtracting an idler gear.

              Found a picture of your lathe here:
              http://bbs.homeshopmachinist.net/showthread.php?t=41724

              Looks good. You have a 127 tooth gear so you can do inch/metric. You have a tumbler reverse. You appear to have a 4th axle, pivoted out of the way. You have 7 gears on the lathe, plus the aforementioned box of gears.

              Start by checking your tumbler reverse and make sure that the axle nearest the spindle (the one coming from the tumbler reverse) rotates exactly once per spindle revolution. It can cause confusion if it does not.

              In the configuration shown in that picture, the middle gears are just acting as an idler and it is doing inch/metric conversion because the 127 tooth gear is in play (actually, it may be a useless setup because the 127 tooth is in the wrong place if your leadscrew is really metric). The second gear on the middle axle is just acting as a spacer. The stack of gears in the back are doing nothing. You appear to have a spacer on the outside end of the leadscrew shaft.

              There is a good chance that when not doing imperial/metric conversion your gear setups may be fairly simple for standard threads.

              If you need help with the gear combinations, post your lead screw pitch and the number of teeth on each change gears you have available.

              Comment


              • #8
                Originally posted by john hobdeclipe
                The old standby is the South Bend book, "How to Run a Lathe." But I think the Atlas (Craftsman) book "Manual of Lathe Operation and Machinists Tables" gives a clearer explanation of change gears and threading operations.

                Check eBay and/or Amazon.
                Or....here is a free equivalent of "How to Run a Lathe" ....

                "Text Book of Turning" by P.T. Hercus

                http://bbssystem.com/viewtopic.php?t=89

                Comment


                • #9
                  [QUOTE=djc]The 'Screw-cutting in the lathe' book by Martin Cleeve (as already suggested but this time with slightly better spelling) is excellent.

                  That will teach me to recommend a book I haven't looked at in a couple of years, without checking first.

                  Comment


                  • #10
                    Originally posted by Mike Burdick
                    Or....here is a free equivalent of "How to Run a Lathe" ....

                    "Text Book of Turning" by P.T. Hercus

                    http://bbssystem.com/viewtopic.php?t=89
                    Excellent! Thanks for this link.

                    Comment


                    • #11
                      In Machinery's Handbook 23rd Edition there is a section in the contents titled 'Threads and Threading' with a subsection titled 'Tapping and Thread Cutting' which contains information on 'Change Gears for Thread Cutting'.

                      If you have a copy of Machinery's Handbook you already have the info that you need to figure what gear combinations you will need to cut any thread pitch that you need.

                      gumper

                      Comment


                      • #12
                        Thank you for the links and pictures. I am studying now!
                        Location: The Black Forest in Germany

                        How to become a millionaire: Start out with 10 million and take up machining as a hobby!

                        Comment


                        • #13
                          What would you like to know about change gears...Just as me!

                          Ok. If any of you need any advice on change gears I am the go to guy!

                          I know everything there ever was or ever will be known about change gears. I am the Google of change gears. I know every size of every make of every system on any lathe ever built or will be built.

                          I am your Change Gear Guru.....

                          Thank you for all the great info. I have been reading most of the afternoon and I think I will try tomorrow to cut some threads on this 100 year old relic.

                          It is not often I get a chance to relax like I did this afternoon.
                          Location: The Black Forest in Germany

                          How to become a millionaire: Start out with 10 million and take up machining as a hobby!

                          Comment


                          • #14
                            Black Forrest.

                            PM box full.
                            .

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



                            Comment


                            • #15
                              Well damn John, if you would stop sending me messages my box wouldn't be full.
                              Location: The Black Forest in Germany

                              How to become a millionaire: Start out with 10 million and take up machining as a hobby!

                              Comment

                              Working...
                              X