I would just think of the bed as a casting, discard the rubbish sitting on it, add a couple of rails and slides now you have something than can carry a saddle without tightening and play.
Dave Caroline On 29/09/2014, Marcus Bowman <marcus.bow...@visible.eclipse.co.uk> wrote: > Would a better solution ( or an as_well_as solution) be to have two saddles > spaced widely apart? > Or maybe we should all just save up and buy a Tormach. Slant-bed doesn't > solve the basic problem, but its a good way to go. > > Marcus > > On 29 Sep 2014, at 03:35, Gene Heskett wrote: > >> On Sunday 28 September 2014 21:54:25 andy pugh did opine >> And Gene did reply: >>> 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? >> >> The requirement for a totally backlashless coupling between the screws? >> >> I too have a similar problem with my toy 7x12. And because the gibs are a >> >> cast iron bitch to adjust, I've considered pulling the no longer used >> rack, and adding an at least as long as the H wings bar front and back and >> >> putting small ball bearings on some sort of adjusters to ride the bottom >> of the front lip and back lip, which should reduce the friction from >> trying to keep the gibs tight enough. Its slightly compounded on this >> early 7x12 as the angle faces on the front of the way, and the angle cut >> in the saddle didn't match by several degrees. With a front gib pulled up >> >> tight, and the rear one off, the back of the H is lifted, originally about >> >> 3/16", now maybe 5 thou. >> >> I milled that out to a better fit and its wearing in nicely over the last >> >> 5 years, nearly stabilized. But with a QC toolpost, the offset from the >> hold down bolt causes the tool to overhang the front of the H and heavy >> cuts lift the right of it a thou or 2. >> >> OTOH that does seem like an awful lot of work as I'd still have a sows ear >> >> lathe. >> >> Bolton has an 11x28 (23 between centers) with a variable speed motor that >> >> sells bare for about $3000 USD. The B290VF. Marked down some now. $2721 >> w/6" 4 jaw & backplate. What can this group say about it? Good or bad? >> >> Is it worth putting ball screws in it? >> >>> 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. >> >> >> Cheers, Gene Heskett >> -- >> "There are four boxes to be used in defense of liberty: >> soap, ballot, jury, and ammo. Please use in that order." >> -Ed Howdershelt (Author) >> Genes Web page <http://geneslinuxbox.net:6309/gene> >> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS >> >> ------------------------------------------------------------------------------ >> 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 >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users > > > ------------------------------------------------------------------------------ > 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 > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
