On Thursday 29 June 2017 19:00:15 andy pugh wrote: > On 29 June 2017 at 23:12, Gene Heskett <[email protected]> wrote: > > yes, momentarily Andy, but it right back as soon as the speed > > steadies, > > Don't let the speed steady? > > https://www.youtube.com/watch?v=dXR2wDDFFm4 > > Are you running a tailstock centre? if tightening that (which, > depending on the bearing type, might preload the head bearings) then I > would suspect the head bearings. > > What type of bearings do you have?
Bronze with adjustable by shims caps. No shims at all in the rear, left end, and 4 mills or so in the front,right caps after some adjustments &_ monitoring with an IR thermometer. Any tighter and the heat rise at speeds above 500 rpms seems too much. It came into my possession with at least 20 thou of slop in the left bearing, and perhaps -3 thou too tight in the right bearing which ran burn your fingers hot. Ed Nisely was nice enough to donate some shim stock he no longer needed, nearly a year back. Between that and some Reynolds Wrap I thought I had it pretty close. > http://www.lathes.co.uk/sheldon/index.html doesn't seem to say. Various production runs had different bearings according to John Knox on that mailing list. And many times the manuals that might come with it have bogus bearing info. Such was the case with the in the desk spindle drives, the countershaft bearings may be shown as torrington needle cartridges, but mine came with a single oilite bushing long enough to fill the space that a pair of torringtons plus a space in the center for grease distribution. That didn't work so well when it was setup with grease zerk fittings, the viscosity of the grease created a lot of heat. On disassembly to drive out the bronze and pull the torringtons back in, I found the real problem was the lower pulley carrying the two belts that spin the spindle, had been reversed on the shaft, so the key was not even in the slot, and the setscrew that was supposed to be locking the key in place, was the only thing spinning the pulley with the shaft, with at times obvious slippage which also generated heat that telegraphed to the outer pulley and into the bearing pockets of the belt tensioning yoke. Made the belts stink like hot rubber etc etc. So I made a browning style tapered collet in the left face of the pulley because thats the only chance I had of making it run semi-true on the shaft, due to both the shaft wear, and wear in the plain hub of the pulley. That shaft would be simple to make but is RC60+, so its quite close to being made from un-obtainium as there is no more N.O.S. of it left on the planet according to John Knox. 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
