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Stepperhead 2

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  • #16
    thanks...I see how the TS is supported now, didn't pick up on that in the rendering
    in Toronto Ontario - where are you?


    • #17
      The bed semi-circular groove is lower than the facing saddle semi-circular groove by a small amount creating an offset aperture between the fixed and sliding surfaces. The oval gib has a profile that closely matches but is slightly smaller than the aperture profile to permit insertion. The gib is rotated to set the sliding clearance and is then set in this position. Further rotation will lock the slides together.
      I'm reading that as a line of contact rather than a area of contact. To my thinking I see the line of the gib and way wearing out faster than a classic dovetail style gib which has more area of contact and thus will work with a film of oil being the usual anti-wear shim between gib and way. Not so with your idea due to the line of contact rather than area of contact.

      My other area of confusion is the way the cross slide hand wheel and screw are offset over to the side from the cross slide. I'm guessing that the similar tooth belt runs under the cross slide?

      Aside from this and a few other niggles I do like the setup. I feel that your design has a lot to offer. And in a more perfect world perhaps instead of the present line of 7x nn lathes as table top machines we'd have something more like your Stepperhead concept. Certainly something more like this would end up being a far more versatile small table top machine.

      For a machine that is moved from spot to spot on the table I've always liked the idea of the Cowell's lathe and others that share the monopad mounting arrangement. On small table top lathes this style over others with two foot pads makes a lot of sense. It avoids the risk of a variable twist in the bed as it's moved around and set in place on uneven surfaces.
      Chilliwack BC, Canada


      • #18
        Hi BCRider,
        I am going to say that it is not a line of contact but an area of contact but this could be argued forever without me revealing the patent details. I also mentioned that," I also have a design (not revealed here) that matches both grooves exactly, regardless of the offset distance." But it would not be sensible to reveal it here due to patent confidentiality. The design for the cross slide is very similar to that shown here
        I think the bed could be made stiff enough to avoid the problems you mention about mounting the lathe on uneven surfaces. Screenshot shows cross slide drive with top cover and stepper drive housing removed.
        Alan Click image for larger version  Name:	18-Cross slide drive - top plate removed.jpg Views:	2 Size:	319.4 KB ID:	1930224
        Last edited by jackary; 02-24-2021, 06:03 AM. Reason: Spelling


        • #19
          i noticed this machine several years ago but never got around to really study it. what would you say are the three main outstanding/different/superior elements of design?


          • #20
            As I understand your concept:

            The oval gib is essentially two cylindrical sections with their center axes a small distance apart. As you rotate the gib within the mating cylindrical groove in the bed, the other side of the gib will trace an arc. If the desired gib position falls on that arc then all should be good.

            This is what I meant by "redundant constraint" just using more words.

            If the desired gib position does not fall on that arc then there will be compromises elsewhere. Lifting carriage off bed or line contact in the gib are likely. Or minimal ability to compensate for wear.

            Of course, this is all dependent on fitting. You have already shown it's possible.

            I'd love to see more details if you are willing to share


            • #21
              It sounds like this idea is more clever than my first look over and reaction. So well done there. And with that last bit of additional explanation I think you're onto a great idea. Details are still a touch cloudy but then that's why it's you submitting for the patent and not me...

              The offset drive to the cross slide is brilliant. A trifle complex and parts heavy if you're aiming at a lower price point but for a product which would go for somewhat more cost and a customer that would appreciate the feature it's freaking brilliant. But sadly I'm thinking that all these innovative and clearly well thought out options are going to raise the price point well above this hobbyist's budget. If/when it comes to fruition I'm afraid I'll be watching and cheering from the sidelines as I move into the two bedroom place where they strain my Pablum for me and I have to downsize to "table top machinist".
              Chilliwack BC, Canada


              • #22
                Hi dian,

                Of course I am bound to be biased, but if you ask me for three different elements compared to a similar size conventional lathe, I would list them like this.

                1) The ability to be able to raise the head and tailstock enables the machine to be used as a light milling/boring machine and the overarm with its integral tailstock stiffens up the headstock and bed and also frees up the bed area usually occupied by the tailstock.

                2)The headstock arrangement with the large pulley outside of the bearings enables a back gear ratio without having a secondary back gear spindle etc. and the built in stepper motor drive to the spindle enables indexing and can be coordinated with the stepper motor X and Z drives for all sorts of spiral machining.

                3) The saddle drive leadscrew operates centrally and high up to move the saddle without the tendency to racking, this helps to create a good finish and the cross slide drive has adjustment for backlash and has a long travel.

                I think that may be more than three things but I did say I was biased.



                • #23
                  Hi B C Rider,

                  Thank you for you kind comments. I too am at the stage where I maybe watching at the sidelines ah well! To try to justify your very valid comment about the cross slide complexity I had previously wrote this-

                  The cross slide handwheel drive is set at an angle to the cross slide and has thrust bearings and the provision to eliminate backlash. The stepper motor can be engaged or disengaged by the lever next to the feedscrew handwheel.

                  One advantage of this system is that the cross slide has a travel equal to the full length of the cross slide and is not restricted by the position of the cross slide handwheel. Another gain is the ability to set the backlash to a minimum. By releasing the screws locking the wormwheel pivot, the wormwheel becomes free to move between the converging axes of the handwheel worm and the feedscrew connected to the cross slide.

                  Rotating the feedscrew handwheel clockwise will cause the wormwheel to wedge between these converging axes and anti-clock rotation will move the wormwheel away, increasing the backlash. By manipulating this, the backlash can be set to a minimum, then the pivot screws are locked to preserve this setting. This enables the backlash adjustment to be easily managed.

                  The drive arrangement for the crosslide may look slightly complicated. But, just to be fair, consider the cross slide drive arrangement for a conventional lathe. From the spindle, a chain of three or more gearwheels transmit the drive to a feed gearbox, then to a long horizontal shaft with a keyway along its length, to drive a sliding gear/worm assembly which can then be engaged to the cross slide feedscrew via an engagable wormwheel and gear arrangement. On many lathes this horizontal shaft is also the leadscrew with a keyway groove cut through the screw threads - not an ideal combination!


                  Last edited by jackary; 03-02-2021, 07:18 AM.