Hobbymat tumbler gear instructions

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Hobbymat tumbler gear instructions

Home Forums Help and Assistance! (Offered or Wanted) Hobbymat tumbler gear instructions

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  • #33312
    Phil Pemberton
    Participant
      @philpemberton74433
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      #381481
      Phil Pemberton
      Participant
        @philpemberton74433

        Hi,

        Some time ago I picked up a "tumbler gear" (screwcutting reversing gear) kit for my Hobbymat MD65. Unfortunately in the time between "receiving the tumbler" and "receiving everything else I need to refurbish the lathe", the instructions have gone missing!

        Does anyone happen to have a copy they could scan or photocopy for me?

        I've put some photos of the gear assembly here: https://imgur.com/a/3RsrPxG
        I have a poor photo of the first half of the first page of instructions from the ebay listing, but that's it – no installation instructions or cutting guide for the gearbox cover

        Thanks,
        Phil.

        #421038
        PETER ROACH
        Participant
          @peterroach92938

          Phil,

          Did you locate any instructions or have you figured it out?

          Peter

          #421043
          Phil Pemberton
          Participant
            @philpemberton74433
            Posted by PETER ROACH on 26/07/2019 17:13:55:

            Phil,

            Did you locate any instructions or have you figured it out?

            Peter

            Hi Peter,

            Sadly not. I found a copy of the installation instructions but sadly the change gear list and diagram are unreadable. The gear list seems to be different to the one on the machine.

            Cheers,

            Phil

            #421254
            PETER ROACH
            Participant
              @peterroach92938

              Phil,

              Any chance of a copy of what you did find?

              I was given one of these lathes, which I believe was acquired 2nd hand from Essel in 2001, that has been modified with the addition of two extra motors. One a Parvalux with a right angle reduction box is fitted with an elephants foot. On the back of the dog clutch is a face plate with an "O" ring. If the power feed lever is pushed to the right the elephant foot drives the face plate via the "o" ring "clutch plate". There is an extra brass sleeve over the clutch lever pillar that engages with a switch so that as well as connecting the drive a switch is made and power feed to the motor. However with all this fitted changing the leadscrew change wheel is a bigger deal.

              I have the following changewheels, 20,30,35,40,50,55,60,65,70,75 & 100. I have also rewritten a BASIC programme to look for other and more accurate combinations. I have 3D printed in ABS a further gear of 63.

              Whilst the Parvalux motor is an elegant solution was looking at the tumbler as a simpler solution.

              Peter

              #421369
              Roger B
              Participant
                @rogerb61624

                I have a Hobbymat fitted with the tumbler reverse so I can supply pictures and measurements if this is of any help.

                #421378
                PETER ROACH
                Participant
                  @peterroach92938

                  Roger,

                  Pictures and measurements would be very useful please.

                  Peter

                  #421489
                  Roger B
                  Participant
                    @rogerb61624

                    I have put some pictures in an album called Hobbymat. The reverser was fitted to the lathe when I bought it. It appears to offer a reversible fine feed but for screwcutting I have always gone back to the original pieces.

                    If this is what you have I am happy to dismantle things and take more pictures/measurements.

                    #421508
                    PETER ROACH
                    Participant
                      @peterroach92938

                      Roger,

                      Thanks, has cleared up that it is either/or and not both. I can understand going back to the original for SC, since it not actually a screw cutting reversing mechanism, which was mentioned as, at the top of thread. I have started to draught the layout in CAD and should be able to calculate the dimensions.

                      Peter

                      #422338
                      Phil Pemberton
                      Participant
                        @philpemberton74433

                        Hi Peter and Roger,

                        I've uploaded the two images I have into an album. Unfortunately there's a page missing but after some cleanup they're mostly readable.

                        #422371
                        Roger B
                        Participant
                          @rogerb61624

                          Thank you smiley

                          #422373
                          PETER ROACH
                          Participant
                            @peterroach92938

                            Thank you

                            #655383
                            eric fritz
                            Participant
                              @ericfritz

                              Hello all.

                              I have joined this site with intrest in the topic of this thread, the reversing tumbler gear attachment.

                              There are several people who would like to duplicate this for their latyhe but lack drawings to do so.

                              Would anyone be willing to provide detailed drawings/measurements for us to do so?

                              Thanks in advance.

                              #655391
                              Martin Connelly
                              Participant
                                @martinconnelly55370

                                For the purposes of threading what the tumbler gears do is effectively make it easy to add an extra idler gear in to the gear train then revert to normal RH threading afterwards. Unless you are going to be doing a lot of LH threading then reverting to RH a modification that allows you to add an idler gear into the gear train, when the odd occasion requires it, would be a simple solution. If you are planning to do a lot of feeding outwards when facing or towards the tailstock when surfacing this may be all that is required.

                                Martin C

                                #655563
                                eric fritz
                                Participant
                                  @ericfritz
                                  Posted by Martin Connelly on 06/08/2023 17:41:46:

                                  For the purposes of threading what the tumbler gears do is effectively make it easy to add an extra idler gear in to the gear train then revert to normal RH threading afterwards. Unless you are going to be doing a lot of LH threading then reverting to RH a modification that allows you to add an idler gear into the gear train, when the odd occasion requires it, would be a simple solution. If you are planning to do a lot of feeding outwards when facing or towards the tailstock when surfacing this may be all that is required.

                                  Martin C

                                  Im a toolmaker by trade and would enjoy the added versatility this mod would offer. Im trying to make this small lathe as capable and easy to use as the full size machines I use regularly.

                                  Having a gear to add or remove is not what I would prefer, Although that would be the "Simplest" thing to do, from a usability standpoint this would get tiresome.

                                  Thanks for the input though.

                                  #655637
                                  Peter Ellis 5
                                  Participant
                                    @peterellis5
                                    Posted by eric fritz on 06/08/2023 16:36:43:

                                    Hello all.

                                    I have joined this site with intrest in the topic of this thread, the reversing tumbler gear attachment.

                                    There are several people who would like to duplicate this for their latyhe but lack drawings to do so.

                                    Would anyone be willing to provide detailed drawings/measurements for us to do so?

                                    Thanks in advance.

                                    Did anyone provide the drawing of the tumbler revers, please ?

                                    #655651
                                    Phil Pemberton
                                    Participant
                                      @philpemberton74433

                                      Sadly I haven't got a drawing but I do have the (unfitted) tumbler mechanism and could take measurements or scans if that'd help. My measuring instruments are limited – I have a micrometer, a set of digital calipers, a Mitutoyo DTI and the usual rulers and so on. No fancy kit like surface plates, sadly.

                                      What I'd really like is a copy of the bits of the instructions which I'm missing – notably the gear ratios. But I expect someone smarter than I could sit down with the drawings, leadscrew pitch (I imagine someone knows that) and scans and figure things out.

                                      If you take a look at the 2 photos I uploaded to my album, they have the two pages of the gear ratios which I have, there's another half-page of additional gear ratios I'm missing.

                                       

                                      Of course what I really should do is put all the stuff I posted to the Hobbymat mailing list on my website – that includes a really nice cleaned-up PDF scan of the lathe manual which is very easy to read when blown up to A4 size!

                                      Edited By Phil Pemberton on 08/08/2023 16:58:05

                                      #655665
                                      Howard Lewis
                                      Participant
                                        @howardlewis46836

                                        Once you know the pitch of the Leadscrew, (Rotate 10 turns and measure how far the Saddle moves ) should enable you to calculate the pitch of the Leadscrew.

                                        Knowing this it should be fairly easy to work out what ratio is needed to cut a particular pitch.

                                        You will find the contents of one or both very useful reading:

                                        Workshop Practice Series No 3, "Screwcutting in the Lathe" by Martin Cleeve.

                                        Crowood MetawWorking Guides "Gearing of Lathes for Screwcutting" by Brian Wood

                                        Having said that, with a small lathe it is likely that many of the threads can be produced using Taps and Dies.

                                        Picking numbers out of the air, for some examples, it will go something like this.

                                        Leadscrew pitch = 1.5 mm

                                        Required thread is 1 mm.

                                        So Leadscrew needs to rotate at 2/3 the speed of the work in the chuck

                                        Possible changewheel set up could be 20 Driver, Idler 60, Leadscrew 30

                                        Could equally well be Driver 50, Idler 20, Leadscrew 75, as long as the gears all mesh correctly.

                                        Required pitch 0.75 mm

                                        Leadscrew needs to rotate at 1/2 of the speed of the workpiece.

                                        so, possible set up

                                        Driver 30, Idler 50, Leadscew 60

                                        or Driver 20, Idler 50, Leadscrew 40

                                        If you want a thread of the opposite hand, just insert an additional idler. Since it will not affect the overall ratio, anything that fits will fit in, say a 20 or 35.

                                        A 63 changewheel would enable you to cut Imperial threads (With some slight, but not necessarily ruinous inaccuracies ) on a lathe with a Metric Leadscrew.

                                        If you just want a fine power feed, how about setting up:

                                        Driver 20, Idler 100 / 30, Leadscrew 75. That should provide a feed of 0.12 mm per rev (0.00472/rev in old money&nbsp ? Hopefully, the stud and key will be long enough to allow you to compound the 100 and 30 wheelswith a pacer to put the Leadscrew gear into correct mesh with the compound Idler.

                                        For setting backlash, (To avoid noise and wear, no geartrain should devoid of backlash ) just run a piece of paper (About 0.75 mm ) between the gears. Start with positioning the stud to set the Leadscrew / Idler mesh and then swing the banjo to set the Idler / Driver mesh.

                                        HTH

                                        Howard

                                        #655732
                                        Bazyle
                                        Participant
                                          @bazyle

                                          Phil,perhaps you can also post hte picture you have of hte unit on here to make it easier to see that going off to imgur.

                                          The device appears only to be intended for variable feeds, not screwcutting as the spacing fixes the final gear to leadscrew at 100. The picture you have is missing the 20tooth on the stud, which has to be compounded with Z1 in the table. W is the mandrel gear.

                                          Referring to Phil's picture (when available) it shows 4 gears of 20 tooth on a sub plate and a stud on the main plate behind coming through a slot. The sub plate pivots about the gear second from left.
                                          The stud should have a 20 tooth gear meshing with the leftmost gear in this position. When the subplate is pivoted the left gear moves out of mesh and the rightmost gear moves into mesh. The gears are 1 module so separation is 2cm.
                                          The pivot point gear has to mesh with a 100 tooth on the leadscrew (coming through the big hole near the bottom) so that spacing must be 5cm+1cm.
                                          The slot in the bottom is for the clamp so measure from your own lathe.

                                          #656269
                                          eric fritz
                                          Participant
                                            @ericfritz
                                            Posted by Phil Pemberton on 08/08/2023 16:57:02:

                                            Sadly I haven't got a drawing but I do have the (unfitted) tumbler mechanism and could take measurements or scans if that'd help. My measuring instruments are limited – I have a micrometer, a set of digital calipers, a Mitutoyo DTI and the usual rulers and so on. No fancy kit like surface plates, sadly.

                                            What I'd really like is a copy of the bits of the instructions which I'm missing – notably the gear ratios. But I expect someone smarter than I could sit down with the drawings, leadscrew pitch (I imagine someone knows that) and scans and figure things out.

                                            If you take a look at the 2 photos I uploaded to my album, they have the two pages of the gear ratios which I have, there's another half-page of additional gear ratios I'm missing.

                                            Of course what I really should do is put all the stuff I posted to the Hobbymat mailing list on my website – that includes a really nice cleaned-up PDF scan of the lathe manual which is very easy to read when blown up to A4 size!

                                            Edited By Phil Pemberton on 08/08/2023 16:58:05

                                            Phil, have you had any time for this yet? I sent you and some others in the thread a PM about this.

                                            Basic measurements for the layout would be very helpful even if not perfect, I could refine them from there and share with the group once I have it working on my machine.

                                            Overall length, width, thickness, the pivot hole location and the pin boss locations for the gears along with the gear rack pivot location would suffice.

                                            #656511
                                            Roger B
                                            Participant
                                              @rogerb61624

                                              I will try to take some measurements of my tumbler reverse over the next couple of evenings. I don't think that there are many critical dimensions.

                                              #656754
                                              Roger B
                                              Participant
                                                @rogerb61624

                                                I have dismantled and measured my tumbler reverse and have drawn it in DraftSight but there dosen't seem to be a way to upload a .dwg file.

                                                The various sectors and large holes are quite rough, possibly plasma or water jet cut.

                                                front.jpg

                                                back.jpg

                                                rough finish.jpg

                                                idler gear.jpg

                                                tumbler reverse.jpg

                                                tumbler reverse gears.jpg

                                                I can send the .dwg by email if requested.

                                                #656806
                                                Peter Ellis 5
                                                Participant
                                                  @peterellis5

                                                  Thank you. Yes please for a DWG.

                                                  peter dot ellis at croatiapropertyservices dot com

                                                  #656816
                                                  eric fritz
                                                  Participant
                                                    @ericfritz

                                                    Yes, thank you so much.

                                                    Sent you a PM with my Email addy.

                                                    #656817
                                                    Phil Pemberton
                                                    Participant
                                                      @philpemberton74433

                                                      Very nice work, Roger!

                                                      Could you please send a copy of the DWG to me at philpem at gmail dot com?

                                                      I'd be happy to host it on my website at https://www.philpem.me.uk/machining/md65 with appropriate credit if you'd like.

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