On Sun, Sep 28, 2014 at 9:54 PM, andy pugh <[email protected]> wrote:
> My lathe is rubbish. That's just a fact. Luckily the lathe is a rather > clever mechanism and even a bad one can make decent parts due to > fundamental precepts of geometry. > > What I noticed today was that the saddle can twist. I think I have the > rear gibb a bit tight for anywhere more than 5" from the chuck. The > fact that there is a gibb is my own upgrade, the OE arrangement was > some cast iron plates with screws that were not quite tight onto a > painted surface (did I mention that my lathe is rubbish?) > > So, I started thinking, and it occurred to me that whilst the > traditional lathe solution to the fact that the leadscrew is offset > from the point of action of the tool is to have a saddle with long > wings, you could have a short saddle that only controls in X with dual > ballscrews to keep X perpendicular to Z. > > I _think_ that this makes some things easier, as you can have a short > saddle which makes missing the head easier, and leaves more room for > the screw covers. And, you can adjust the X-Y squareness, which is > normally impossible. > > Apart from the extra cost, what is the drawback? > > This isn't the same as a central leadscrew, by the way, that's nice, > but in that scenario too, the scew can't keep the saddle square. > > > > -- > atp > Andy, Are you thinking of starting from scratch with bits and pieces - say the headstock and drive motors? If so, why not pour an epoxy-granite base, mount your headstock to that, and use linear rails instead of depending on a cast iron bed that can twist and wear. You can still use two lead screws, or two rack and pinion's (or would that be racks and pinions, or ... ;-)) to drive the carriage. The linear rails mounted to the epoxy-granite bed would certainly be a heck of lot stiffer, and would be great at dampening things that would cause chatter and such. Mark ------------------------------------------------------------------------------ Slashdot TV. Videos for Nerds. Stuff that Matters. http://pubads.g.doubleclick.net/gampad/clk?id=160591471&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
