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. -- -Mark Ne M'oubliez ---Family Motto Hope for the best, plan for the worst ---Personal Motto ------------------------------------------------------------------------------ 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
