Design fault in SC2 mini-lathe topslide actuation?

hello this is a short video about a problem I found on the sc2 lathe affecting the top slide which i think is a design fault those of you who are looking for more progress on robot boat sailing boats I'm still working on the servo but I'm not yet ready to disclose any further progress not quite tight so it doesn't have much movement but you look at it very closely you might be able to see very slight movement here or at the Kip so basically I can't afford to make it any looser than that so aquatic learners up as tight as I reasonably can but I can still move it in and out like that but what I noticed is if we look at this micrometer dial which of course is a friction coupling to the handle and the shaft if I move it this way the micrometer moves correctly with the handle and the shaft but if I move it that way it does not wear as on the cross slide it moves correctly so I wonder why that was and I seem to be in a situation where I forgot to have the top slide to loose from the point of view of unwanted movement in order to allow this micrometer dial to move as it should do and I looked at the design of it and discovered there's a fundamental design mistake here which isn't present in the topside which isn't present in the cross slide if we look at the cross slide you've got a screw that if we turn it clockwise comes out and you can turn down clockwise it goes in now that movement is constrained by this flange here which if I turn it anti-clockwise bears upon this surface and if I turn it clockwise it bears upon this surface here which is bolted to the rest of the thing so the movement in and out of this spindle is constrained by this flange operating between this surface and that surface and in fact there is very little backlash in that but therefore as we turn the spindle what actually happens is that the cross slide moves rather than the spindle moving which is absolutely fine because of that arrangement when I put the additional components on the micrometer dial and the handle there is no force applied on that dial as I turn this the force is taken on the flange in here rather than on that dial so but she's explained why it works correctly look at the top slide we have exactly the same arrangement with a spindle and the flange on it and as I rotate the spindle anti-clockwise that flange bears upon this surface here which is bolted which is bolted to the top slide and thus as I turn this anti-clockwise the top slide is pulled to the right the problem lies in the fact that when I turn this clockwise there is absolutely nothing restraining restraining that flange see we got free air here there's nothing restraining the flange whereas on the cross slide it was bearing upon a surface and it's that absence of restraint as I turn this clockwise which causes the problem because when we put these other components on I just fit it temporally so in this peculiar arrangement if I turn this anti-clockwise that flange that we saw bears upon this which is bolted to that and therefore it drags the top slide to the right and if I turn it clockwise the flange is bearing on nothing and so force in this direction is being applied via these two surfaces here the handle is pushing on that washer which is pushing on that which is pushing on that and so whether or not this turns depends on whether this friction which is provided by a spring as you know inside here whether that friction is greater or less than the friction between here and here as we try and push the top slide to the left obviously the tighter I do this up the more force between these two surfaces the greater this friction and that's why this micrometer dial is not turning as it should do we can see that if we look underneath looking at this underneath when we turn the screw anti-clockwise this flange bears upon that which is bolted to the top slide and therefore drags the top slide to the left but when we turn it clockwise there is absolutely nothing restraining this flange therefore the handle pushes this micrometer against that that sort that's how the top side has moved to the left what this should be is a piece of metal here fixed to the top slide to which that flange can engage just as there is on the cross slide as I showed you earlier so whoever designed this top slide arrangement simply forgot that there needs to be constraint in both directions this this shaft needs to be constrained in both directions and fit not fixed but so that the flange can apply a force to the top slide and they've just forgotten so what I've done an attempt to fix this problem is I've made this little block which just bolts on to the underside of the top slide at the right-hand end I mean to these two holes that I've tapped there and the screw fits in there and this flange is now trapped between these two pieces of metal so if I unscrew the screw this one drags the top slide that way and if I screw it in this one pushes this top slide that way thereby removing all the pressure on the micrometer the downside of this is that I've had to cut this much off the Gib and therefore I have a centimeter less movement to the right to the left sorry but I don't think that's very important because I never actually want to use the top slide put fully to the left if I did I suppose I would get another game and just unbolt these and go back to the status quo ante well I've fitted that and now I can tighten the top slide as much as I like and it still does not move this indexing the ring which is good the backlash that you can see there is the backlash between the flange which is found on the shaft which is captured between here and the piece of metal that I've inserted I just say it's the backlash between this flange on the shaft and this piece of metal and that piece of metal both of which are bolted to the topside I could reduce that by putting a shim washer in but I'm not much bothered about it the important thing is that I've solved that problem with the indexing disk

Channel: Samuel Fielder

Views: 67,922

Rating: 4.8552279 out of 5

Keywords: mini-lathe, SC2, topslide modification, micrometer dial, sticking

Id: uWMtckdqw88

Length: 9min 34sec (574 seconds)

Published: Sat Dec 23 2017