On Friday 26 January 2018 23:40:40 andy pugh wrote: > On 27 January 2018 at 00:07, Gene Heskett <ghesk...@shentel.net> wrote: > > > As a first measurement, try a dial indicator in the chuck around a > > > good MT adaptor in the tailstock (assuming a set-over tailstock). > > > > That, even with the tailstock that close, is going to be off a good > > 50 thou as I've yet to get shims (and shim stock enough) to get it > > true, its off vertically, and I've also bought 2 more triple bearing > > MT2 centers only to find their NT2's ground off center > > That is why I was suggesting an MT3 - to - 2 adaptor. (Or 2 to 1, if > the tailstock is a 2) > They would have to try very hard to make the outer surface of the same > taper not concentric with itself.
OTOH, if the part such as a dead center, has to be reversed after grinding one end and the other end was done in a different jig or even machine, finding the tip of a dead center out of registration with the axis of the MT-2 is entirely up to the operator and how clean he kept the sockets. Which is why I didn't take a lot of care making the MT-5 and the threads for the drawbar concentric with the piece of raw alu I started with. Verifying that the runout was as close to zero as I could get it in the spindles bore, I didn't care, because when I turned it around and put a few hundred lbs of pull into the spindle with it, it wasn't going anyplace. At that point I made a reversed 5C pattern on the other end of the alu rod and made sure it was a snug press fit, difficult to draw into place with a bolt and some washers in the end of the alu. The washers fit against the cut-away for the drawbar in the rear of the grizzly adapter, giving me free reign to grind and remove enough of it so it didn't hit the teeny ledge in the MT-5 taper in the spindle that the max reach (2.65") of the grinder left. That last was cut .0000625" a pass, with just a few sparks from the stone. Smoother than new once it was cleaned out after correcting the 5C taper wall to 10 degrees. ATM, I think, useing what I brung, that pulling the tailstocks barrel, chucking it in the 4 jaw with very little projecting, adjusting the run-out of its bore with tension on the jaws, then inserting the worn center and giving it a few taps with a dead blow, and re-grinding the 60 degree tip is the best way to get a center good enough to align the tailstock. As for the live centers, I guess I'll have to throw both what I have and bigger money out for a good one. These 2 $22 ones are sure junk. I wouldn't use them within 18" of the chuck, I've already had them make a well tightened workpiece walk in the chuck. At about 10" away. Eventually I suppose I'll get to scraping the 70 years of wear out of the ways, or map it. I'll no doubt ask some questions about that because I'll be mapping the X error according to Z's absolute position. And that changes about half a thou depending on which way Z is moving. That I think might be an artifact of an apron thats about 50 lbs lighter than OEM monster apron holding it on the V. It lost a similar amount of weight on the rear with the removal of the taper assembly, and it may need some bearings to add some preload to the front of the saddle. We'll see... Thanks Andy. -- 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> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
