On Wednesday 22 August 2012 22:28:10 Mark Cason did opine: > On 08/22/2012 06:33 PM, Gene Heskett wrote: > > Hi all; > > > > I am still trying to put that ball screw in the X axis of my > > mini-lathe, and as I was cleaning things up, getting ready for the > > next step of the assembly, I find that I have not fixed a gib problem > > this POS has had since day one, and likely cannot without a new, more > > precisely fitting gib strip. > > > > The first time I ever took it apart, I noted that it was bent, > > swaybacked by about an eight of an inch just laying on the table > > relaxed. > > > > So I got out something resembling an anvil and bent it back as > > straight as I could, then polished it till its wear face was straight > > before I reassembled it, removing possibly .005" in getting the upper > > facing 45 degree angle so it marked a magic marker full length. > > > > Today as I was reassembling it and attempting to adjust the gib > > screws, I noted that the top face not only wasn't in contact with the > > bottom of the slider, the tip of it at the bottom of the carriages > > v-cut was sharper than the bottom of the carriages v-cut, so I > > purposely rounded off that edge hoping that both sides of the V would > > make contact. Such is not the case and never will be with this > > strip, it is not only about 50 thou thinner than it should be, but > > when the angled face is in contact with the V-way, its top face is > > clearing the bottom of the cross slider at a very noticeable angle of > > at least 10 degrees. > > > > If I stick my pocket knife into the gap between the carriage top and > > the bottom of the slider, I can lift the right edge of the crossfeed > > a good 20 thou, which explains a lot of why I can't begin to use all > > the spindle motor for a cut and the bit, when the cross slide tips up > > like that, is driven into the workpiece hard enough to stall the > > spindle & blow the fuse or trip my electronic fuse in .hal instantly. > > I can actually see the gib strip being picked up by the adjustment > > screws, allowing a tip up of at good 20-30 thou by the time the top > > of it is in contact with the bottom of the slider. I can also see > > straight through the clearance gap, both top and bottom. EG this sows > > ear is decomposing. > > > > LMS doesn't show a replacement strip for this lathe, so it appears I > > will need to make a new one. So, 2 questions: > > > > 1: What should I make it out of? > > > > 2: will the usual 45 degree dovetail bit suffice to establish the > > correct angles to contain this lifting of the right edge of the cross > > feed slider? > > > > 3: Or, perchance is this a stock item at some other machinery peddler > > besides LMS? > > > > Thanks. > > > > Cheers, Gene > > A couple of years ago, I completely rebuilt my mini lathe. I > stripped my lathe down, and took med/fine clover compound, and spent > then next hour sliding the carriage from one end of the bed, to the > other. After that, I cleaned it thoroughly. > > To fix the wavy bottom edge of the ways, I took some 240 grit > sandpaper, and glued it to the gib strips. and then slid the carriage > back, and forth again, for the next 2 hours, changing to increasingly > finer sandpaper every couple hundred strokes, or so. I finally ended > with a piece of 1000 grit. I added a bit of machine oil to the ways, > top, and bottom, to make sliding the carriage easier. Adjust the gib > screws to the point that you have resistance, but not too tight that the > carriage won't move easily. > > Finally, I took and machined, and lapped a new gib strip out of a > 1/4" piece of mild steel. The gib should be machined so that you don't > need to use the adjustment screws. Measure how much your carriage > extends above, or below the bottom edge of the ways, and machine the gib > accordingly. Brass, would be a ideal material, but pretty much any > metal will work.
Carriage under bed flange gibs aren't a huge problem, yet... This is the cross slider gib, under the 3 adjustment screws on the right side of the slider. Its a POC, with machining marks from an extremely worn to the point of galling the surface cutting tool on every face but the actual contact face I have flattened on a surface plate, and every angle on it seems totally unrelated to reality. The whole right side of the slider can be tipped up about 20 thou, rocking the gib on the points of the adjusting screws with perhaps 50 lbs of lift. No trouble at all to stick my pocket knife blade under it and watch it move on a dial indicator. And this is with all 3 screws set in to finger tight & locked. I have to use a dead blow hammer to move it, but I can still lift it. I can pick up the whole assembly and see daylight both under it, and over it, all the way thru from front to back, 40 to 50 thousandths of daylight. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! Dopeler effect: The tendency of stupid ideas to seem smarter when they come at you rapidly. ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
